The Axial SkeletonThe Skull

General Features of Skull:

♣ The expanded upper part of axial skeleton lodging the brain and covering meninges.

♣ Consists of 22 bones, the mandible being the only mobile bone forming the TMJ.

♣ Descriptively divided into a globular upper part called cranium consisting of 8 bones, and an irregular anterior lower part called facial skeleton forming of 14 bones.

♣ The cranium has cranial cavity for the brain & meninges, and formed by:

♠ Single frontal bone ♠ right & left parietal bones ♠ Right & left temporal bones

♠ Single occipital bone ♠ Single sphenoid bone ♠ Single ethmoid bone

♣ The facial bones include:

♠ Two nasal bones ♠ Two lacrimal bones ♠ Two maxillae

♠ Two inferior nasal conchae ♠ Two palatine bones ♠ Two zygomatic bone

♠ Single vomer ♠ Single mandible

♣ The cranial vault (cranial cap or calva) is formed by frontal, right & left parietals and occipital bones.

(Cont.)

♣ Except the mandible, all other bones of skull are connected together by immobile suture which at birth allows slight sliding on each other to decrease the size of fetal skull and help in labor.

♣ All bones of skull are made of inner & outer solid plates separated by a spongy bone called the diploë which is active in blood formation throughout the life.

♣ The bones of skull are perforated by foramens, fissures or canals which transmit blood vessels and cranial nerves.

♣ Emissary foramens are small openings in certain skull bones which transmit emissary veins that connect extracranial and intracranial veins, and are the site for intracranial spread of infection (meningitis & encephalitis).

♣ Developmentally, the bones of vault of cranium are developed from ossification into membranes (desmocranium), while the rest of skull bones are developed from ossification of hyaline cartilages (chondrocranium).

♣ The easiest way of learning skull features is via the ways you are viewing it:

♠ Norma Frontalis (anterior view) ♠ Norma Verticalis (superior view) ♠ Norma Lateralis (lateral niew) ♠ Norma Occipitalis (posterior view) ♠ Norma Basalis (inferior view) ♠ Interior of Skull (cranial cavity)

Norma Frontalis

Norma Verticalis

Norma Lateralis

Norma Occipitalis

Norma Basalis

Norma Basalis

Interior of Skull

Internal Features of Cranial Cap (Calva)

Features of the Skull of New Born:♣ The sutures are still membranous

♣ The anterior fontanelle is about 5 cm in diameter lying at the junction of sagittal & coronal suture. It usually ossifies & disappears at 18-24 months of age.

♣ The posterior fontanelle is usually very small or abscent lying at the junction of sagittal & lumbdoid suture. If present, it usually ossifies & disappears at 2-6 months of age.

Mandible

Hyoid Bone

Vertebral Column:♣ Consists of 33 vertebrae divided into 7 cervical, 12 thoracic. 5 lumbar, 5 fused sacral and 4 fused coccygeal.

♣ the vertebral column has 4 curvatures:

♠ Cervical curvature convex forward

♠ Thoracic curvature concave forward

♠ Lumbar curvature convex forward

♠ Sacral curvature concave forward

♣ Their bodies from 2nd cervical to 1st sacral vertebrae are joined together by fibrocartilaginous intervertebral discs to increase flexibility.

♣ Each disc consists of central gelatinous part called nucleus pulposus and peripheral fibrous part called annulus fibrosus.

♣ Prolapsed disc is a common clinical condition due to degenerative changes leading to the herniation of nucleus pulposus through ruptured annulus fibrosus and pressing on the spinal cord or spinal nerve roots causing muscular and neurological symptoms and signs.

♣ The prolapsed disc may occurs any where in vertebral column but, the most common sites are between L4-L5 & between L5 & sacrum.

♣ The deformities in the shape of vertebral column are developmental or acquired degenerative and include: Kyphosis: increased backward curvature of vertebral column. Lordosis: increased forward curvature of vertebral column. Scoliosis: an increase in lateral bending of vertebral column.

Cervical Vertebrae7 in number, all are small in size with quadrangular-shaped vertebral body and triangular-shaped vertebral foramen. They have foramens in their transverse processes for the vertebral vessels ) vertebral veins ascends fron 7th, while the artery from the 6th

Features of Typical Cervical Vertebrae (3-6):♣ The body small & quadrangular♣ The vertebral foramen is large & triangular in shape♣ The transverse processes are broad and short♣ The spine is bifid

Feature of Atypical Vertebrae (1st atlas, 2nd Axis & 7th Cervica Prominence):

Atlas:♣ Has no vertebral body♣ The vertebral foramen is large constricted in middle, divided by transverse ligament into smaller anterior part occupied by dens of axis vertebra, and posterior larger part occupied by spinal cord and meninges.♣ It is modified to fit the base of skull at atlanto-occipital joint.

Axis:

Has all features of typical cervical vertebrae except that its body superiorly has a bony projection called dens or odontoid process which articulate with atlas vertebra in atlanto-axial joint for the rotation of head.

7th Cervical Vertenra:

♣ Has all feature of typical vertebrae except that its spinous process is long, prominent and not bifid.

♣ In a developmental anomaly called Cervical Rib, the transverse processes of the 7th vertebra are long and connected to the first rib by a fibrous cord. This will result in the traction of lower trunk of brachial plexus (C8,T1) causing muscular & neurological symptoms.

The Scalp:

Extension: superior nuchal line, auricles & eyebrows

Layers: skin, connective tissue, aponeurosis of occipitofrontalis muscle, loose subaponeurotic connective tissue, periosteum.

Occipitofrontalis Muscle:

Attachment: highest nuchal line & skin of eyebrows.

Action: moves the scalp to raise or depress the eyebrows in facial expression.

Nerve supply: temporal and posterior auricular branches of facial nerve.

Sensory Nerve Supply of Scalp:

1. Supratrochlear & supraorbital nerves from the ophthalmic division of trigeminal nerve.

2. Zygomaticotemporal nerve from maxillary division of trigeminal nerve.

3. Auriculotemporal nerve from mandibular division of trigeminal nerve.

4. Greater occipital nerve a branch of dorsal ramus of C2

5. lesser occipital nerve (C2) from cervical plexus.

Arterial Supply of Scalp:

1. Supraorbital & supratrochlear branches of ophthalmic artery (internal carotid artery)

2. Zygomaticotemporal branch of maxillary artery (external carotid artery)

3. Superficial temporal artery (external carotid artery)

4. Occipital artery (external carotid artery)

5. Posterior auricular artery (external carotid artery)

Veins of Scalp:

1. Supratrochlear & supraorbital veins forming the facial vein

2. Superficial temporal vein 3. Occipital vein 4. Posterior auricular vein

Lymph Drainage of Scalp:

Submandibular & submental nodes → deep cervical nodes.

Clinical Notes:

♣ Cutting wounds ♣ Subaponeurotic hematoma ♣ Subperiosteal hematoma

♣ Dermoid cyst ♣ Sebaceous cysts

The FaceMuscles of Facial Expression:

♣ Located in the superficial fascia, attached to bones of skull and the skin of face.

♣ Exert sphincteric action around the orbit, mouth and nasal apertures.

♣ Change the expression of face.

♣ No need to memorize their attachments but be familiar with their names and location.

♣ They include;

♠ Muscles Around Orbital Cavity (orbicularis oculi, corrugator supercilii, procerus).

♠ Muscles Around the Nasal Openings (compressor nasi & dilator naris, levator labii superioris alaeque nasi).

♠ Muscles of Lip and the Angle of Mouth (orbicularis oris, levator labii superioris, levator anguli oris, zygomaticus major, zygomaticus minor, depressor labii inferioris, depressor anguli oris, mentalis, risorius, buccinator, platyama).

Orbicularis oculi:

♣ The orbital part is the outermost part, its fibers arise from medial palpebral ligament make a complete circle around orbital opening and insert into the same area of origin. It forcibly closes the opening of eye during the reflex protection of eyes when exposed to foreign bodies or truama.

♣ The palpebral part in the eyelids and its fibers take origin from the medial palpebral ligament and insert into the lateral palpebral ligament. It lightly closes the eyelids as in blinking or during sleep. It also directs the tears medially toward dilated lacrimal sac.

♣ The lacrimal part is small deep part encircle the lacrimal sac and help to evacuate the sac from tears into the nasolacrimal duct.

♣ It is supplied by temporal & zygomatic branches of facial nerve.

Orbicularis oris:

♣ Forms the upper and lower lips.

♣ It takes origin from the outer surface of maxilla and body of mandible

♣ It consists of peripheral & marginal fibers which intermingles with other facial muscles (zygomaticus major & minor, risorius, buccinator and the levators and depressors of lips and angle of mouth) at the angle of mouth forming the modiolus.

♣ Supplied by buccal branch of facial nerve

♣ It controls the movements of lips in drinking, eating, suckling, whispering, whistling, and talking.

Buccinator:

♣ Muscle of the cheek, has the buccal pad of fat on it, and it is pierced by the parotid duct.

♣ Originates from alveolar part of maxilla & mandible and inserts into the pterygomandibular raphe.

♣ Supplied by buccal branches of facial nerve.

♣ It balloons and compresses the cheek.

Platysma:

♣ Broad, sheet-like muscle, and the most superficial muscle.

♣ Arises from the deep fascia over the deltoid and pectoralis major muscles, and inserts into the mandible and the fascia at the angle of mouth.

♣ Supplied by the cervical branch of facial nerve.

♣ It tenses the skin over the side of neck especially in shaving, and depresses the mandible and angle of mouth.

Motor Nerve Supply of Facial Muscles:

♣ All are supplied by the facial nerve through its 5 terminal branches emerging from the substance of parotid gland ( temporal, zygomatic, buccal, marginal mandibular & cervical).

♣ Temporary paralysis of facial nerve (Bell’s Palsy) is common clinical condition affecting young adults and characterized by inability of closing the eye and drop of the angle of mouth on the affected side with passage of fluid out of mouth.

Sensory Nerves of Face:

1) From Ophthalmic Division of Trigeminal Nerve: supraorbital & supratrochlear branches of frontal nerve. infratrochlear and external nasal branches of nasociliary nerve. palpebral branch of lacrimal nerve.

2) From Maxillary Division of Trigeminal Nerve: infraorbital & zygomaticofacial nerves

3) From Mandibular Division of Trigeminal Nerve: auriculotemporal, buccal & mental nerves

4) From Cervical Plexus: great auricular nerve (C2 & C3) which supplies the skin over parotid gland and part of auricle.

Arteries of Face:

1) Branches of facial artery: inferior labial, superior labial, lateral nasal arteries.

2) Branches of ophthalmic artery: supratrochlear, supraorbital, infratrochlear , external nasal and palpebral arteries

3) Branches of maxillary artery: infraorbital, mental, buccal and zygomaticofacial arteries.

4) Branches of superficial temporal artery: transverse facial and zygomatico-orbital arteries

Veins of Face:Facial, superficial temporal and maxillary veins

Lymph Drainage of Face:Into the submental & submandibular lymph nodes which eventually are drained into the deep cervical nodes.

Muscles of Mastication:

♣ They include, masseter, temporalis, lateral pterygoid & medial pterygoid.

♣ All are supplied by mandibular division of trigeminal nerve.

♣ They originate from the skull bones and insert on to the mandible.

♣ They act on temporomandibular joint (TMJ) during mastication and speech.

Masseter: ♣ Originates from zygomatic arch & inserts on the outer surface of angle and ramus of mandible. ♣ It elevates, retracts & protracts the mandible.

Temporalis: ♣ Originates from the parietal bone & squamous part of temporal bone (floor of temporal fossa) and from the temporal fascia.

♣ Inserts into the coronoid process of mandible.

♣ It elevates and retracts the mandible.

Lateral pterygoid: ♣ Its upper head arises from infratemporal crest of greater wing of sphenoid while the lower head arises from lateral surface of lateral pterygoid plate.

♣ It inserts into the neck of mandible and articular disc of TMJ.

♣ It depresses the mandible & opens the mouth.

Medial pterygoid: ♣ It has superficial & deep heads surrounding the lower heads of lateral pterygoid.

♣ The deep head arises from medial surface of lateral pterygoid plate, while the superficial head arises from the tuberosity of maxilla.

♣ Inserts into the inner surface of angle of mandible opposite the insertion of masseter.

♣ It elevates the mandible and closes the mouth

The Temporal Fossa:

♣ It lies deep to scalp at the side of skull.

♣ Extends from superior temporal line to zygomatic arch.

♣ It contains ♠ temporalis, ♠ temporal fascia, ♠ deep temporal vessels of maxillary vessels ♠ deep temporal nerves from mandibular division which supply temporalis ♠ zygomaticotemporal nerve and vessels (branches of maxillary nerve and vessels).

♣ The superficial temporal artery & vein, auriculotemporal nerve, and temporal branch of facial nerve are superficial to temporal fascia.

The Infra-Temporal Fossa:

♣ It lies below and deep to zygomatic arch between the side of skull & the ramus of mandible.

♣ It is communications are:

♠ with temporal fossa deep to zygomatic arch.

♠ with middle cranial fossa through foramen ovale and foramen spinosum

♠ with pterygopalatine fossa at the base of skull through pterygomaxillary fissure.

♣ It contains: ♠ lateral & medial pterygoid muscles

♠ maxillary artery and its branches (mainly, inferior alveolar, middle & accessory middle meningeal arteries & others).

♠ pterygoid venous plexus, maxillary vein and lymphatic vessels

♠ otic parasympathetic ganglion & lesser petrosal nerve.

♠ mandibular nerve, its divisions and branches.

♠ chorda tympani nerve joining the lingual nerve.

Maxillary Artery:♣ Terminal branch of external carotid artery, arises behind the neck of mandible within the parotid gland.

♣ Descriptively divided into three parts; 1st, 2nd & 3rd parts.

♣ The First Part extends from the origin to lower border of lateral pterygoid muscle and gives the following branches: 1. Deep auricular artery to external auditory meatus 2. Anterior tympanic to tympanic membrane 3 & 4. Middle meningeal & accessory middle meningeal arteries to meninges 5. Inferior alveolar artery to mandible which gives (6.) mylohyoid artery to mylohyoid muscle♣ The Second Part usually runs superficial to lateral pterygoid muscle and gives: 7. Muscular branches to masseter and pterygoid muscles 8. Two deep temporal arteries to temporalis 9. Buccal artery

♣ The Third part at the pteygomaxillary fissure gives the (10.) posterior superior alveolar artery to maxilla and (11.) the infraorbital artery. Then it continues into the pteygopalatine fossa and gives the following branches: 12 & 13. Greater & lesser palatine arteries to palate & nasopharynx 13. Pharyngeal artery to nasopharynx 14. Artery of pterygoid canal 15. Sphenopalatine artery (termination of maxillary artery) to palate

The Pterygo-Palatine Fossa:

♣ Very small and deep pyramidal-shaped fossa, located immediately below the apex of orbital cavity.

♣ It lies between the maxilla, pterygoid and palatine bones.

♣ It is communicated with: ♠ infratemporal fossa through pterygomaxillary fissure.

♠ middle cranial fossa through foramen rotundum and pterygoid canal.

♠ nasal cavity through sphenopalatine foramen.

♠ Orbital cavity through inferior orbital fissure.

♣ It contains: ♠ Maxillary nerve and its branches.

♠ Pterygopalatine parasympathetic ganglion & its branches, and the nerve of pterygoid canal (formed by greater petrosal & deep petrosal nerves).

♠ Terminal part of maxillary artery & its branches with accompanying veins and lymphatic vessels.

Deep Fascia of Neck:The deep fascia of neck include four parts; the investing deep fascia, the carotid sheath, the pretracheal fascia and the prevertebral fascia.

1) Investing deep Fascia:

♣ Attached superiorly to base of mandible, mastoid process & superior nuchal line.

♣ Attached inferiorly to acromion process of scapula, clavicle and manubrium sterni.

♣ Superiorly it provides fascial sheaths for submandibular & parotid salivary glands.

♣ It thickens between parotid and submandibular glands forming the stylomandibular ligament.

♣ It invests sternomastoid, inferior belly of omohyoid, trapezius and extends posteriorly to reach the ligamentum nuchae.

♣ It is thin over the roof of posterior triangle and above the manubrium sterni, where the inflammatory pus usually points out to the skin.

♣ In the middle and above the manubrium sterni, it splits into two layers which are attaches to inner and outer margins of manubrium forming the suprasternal space.

♣ The suprasternal space contains: ♠ the sternal heads of sternomastoid muscles ♠ lower parts of anterior jugular veins ♠ the jugular venous arches ♠ a small lymph node

http://upload.wikimedia.org/wikipedia/commons/7/7f/Gray384.png

2) Carotid sheath:

♣ Tubular sheath investing the common carotid artery then internal carotid artery, internal jugular vein, deep cervical lymph nodes, vagus nerve and the ansa cervicalis nerve.

♣ Extends from base of skull to superior mediastinum where it continues with adventitia of great vessels.

3) Pretracheal Fascia:

♣ Invests thyroid and parathyroid glands

♣ Attached to hyoid bone and thyroid cartilage.

♣ It moves the thyroid gland with deglutition

4) Prevertebral Fascia Fascia:

♣ Covers the prevertebral muscle

♣ Extends from base of skull to 3rd thoracic vertebra.

♣ In the root of neck, it gives tubular sheath called axillary sheath which invests axillary vessels and cords of brachial plexus.

Triangles of Neck:The neck is best studied by dividing it into anterior & posterior triangles using sternomastoid as a landmark.

The Posterior Triangle:

♣ Bounded anteriorly by posterior border of sternomastoid, posteriorly by the anterior border of trapezius and inferiorly by the middle third of clavicle.

♣ It roof is formed by investing deep fascia, superficial fascia, platysma, cutaneous branches of cervical plexus and skin.

♣ Its floor is formed by muscles lined by prevertebral fascia, which include from above downward, semispinalis capitis, splenius capitis, levator scapulae, scalenus medius, scalenus anterior and 1st digitation of serratus anterior.

♣ It is divided by the inferior belly of omohyoid into an upper larger occipital triangle and a smaller lower supraclavicular or subclavian triangle.

Occipital Triangle: it contains:

♠ Occipital artery.

♠ Cutaneous branches of cervical plexus (great auricular nerve, lesser occipital nerve, transverse cutaneous nerve of neck & supraclavicular nerve).

♠ Spinal accessory nerve which supplies trapezius & sternomastoid.

♠ Dorsal scapular nerve which supplies levator scapulae and rhomboideus major & minor muscles.

♠ Sensory nerves to trapezius, levator scapulae, rhomboideus muscles from cervical plexus.

♠ Transverse cervical, suprascapular arteries & external jugular vein♠ Upper & middle trunks of brachial plexus.

Subclavian Triangle: it contains:

♠ 3rd part of subclavian artery ♠ Lower trunk of brachial plexus

♠ Transverse cervical & suprascapular arteries ♠ Phrenic nerve

♠ Suprascapular nerve to supraspinatus & infraspinatus muscles, and suprascapular vessels.

♠ Inferior thyroid artery ♠ Long thoracic nerve to serratus anterior muscle.

The Anterior Triangle & Its Subdivisions:

♣ It is bounded by the midline anteriorly, anterior border of sternomastoid posteriorly, and by the inferior border of mandible superiorly.

♣ It is subdivided into submental, digastric or submandibular, carotid and muscular triangles,

The Submental Triangle:

♣ Bounded by midline anterioerly, hyoid bone inferiorly, and the anterior belly of digastric posteriorly.

♣ The roof is formed by skin superficial fascia, platysma & investing deep fascia.

♣ The floor is formed by mylohyoid muscle.

♣ It contains: 1. Submental lymph node 2. Submental vessels 3. Anterior jugular vein

The Digastric (Submandibular) Triangle:

♣ Bounded anteriorly by anterior belly of digastric, posterior belly of digastric & stylohyoid muscles posteriorly and the inferior border of mandible superiorly.

♣ The roof is formed by skin superficial fascia, platysma and deep investing fascia.

♣ The floor is formed by mylohyoid, hyoglossus and superior constrictor muscles.

♣ It contains: 1. Submandibular lymph nodes 2. Submandibular salivary gland 3. Facial artery & vein 4. Submental vessels 5. Mylohyoid nerve & vessels 6. Hypoglossal nerve 7. More posteriorly are the internal & external carotid arteries & vagus nerve.

The Muscular Triangle:

♣ Bounded anteriorly by the midline, superiorly by posterior border of superior belly of omohyoid, and inferiorly by sternomastoid.

♣ Its roof is formed by skin superficial fascia, platysma & investing deep fascia.

♣ Its floor is formed by the inferior belly of omohyoid, sternohyoid and sternothyroid muscles which are supplied by ansa cervicalis

The Carotid Triangle:

♣ Bounded superiorly by posterior belly of digastric, inferiorly by superior belly of omohyoid, and posteriorly by sternomastoid.

♣ Its roof is formed by skin, superficial fascia, platysma and investing deep fascia.

♣ Its floor is formed by thyrohyoid, hyoglossus, middle and inferior constrictor muscles.

♣ It contains. 1. Common carotid artery & its bifurcation 2. Internal carotid artery & internal jugular nerve 3. External carotid artery & its branches (superior thyroid, ascending pharyngeal, lingual, facial & occipital) 4. Deep cervical lymph node 5. Hypoglossal nerve 6. Accessory nerve 7. Loop of ansa cervicalis (C1,2&3 superior root from C1, inferior root from C2 & C3.

Vessels of the Head & Neck

Brachiocephalic Trunk:

● Arises from arch of aorta, ascends upward, laterally and to right side.

● Divides into right common carotid and right subclavian arteries behind the sternoclavicular joint.

● Crossed anteriorly by left brachiocephalic vein.

● The right brachiocephalic vein lies anterolateral, and the right vagus descends posterolateral.

Common Carotid Arteries:

● The right artery arises from brachiocephalic trunk behind right sternoclavicular joint.

● The left artery arises from the arch of aorta, ascends lateral to trachea and enters the neck behind left sternoclavicular joint.

● Both ascends in the neck overlapped by the lower part of sternomastoid, sternohyoid, sternothyroid & superior belly of omohyoid.

● Enclosed by carotid sheath together with internal jugular vein (anterolateral), vagus nerve (posterolateral) and ansa cervicalis (anterior).

● The lower cervical transverse processes, prevertebral muscles, vertebral vessels, inferior thyroid artery and cervical sympathetic trunk lies behind it.

● The trachea, esophagus, recurrent laryngeal nerve, larynx, pharynx & thyroid gland lies medial to it

● Divides at the level of upper border of thyroid cartilage into internal & external carotid arteries.

● It dilates at its bifurcation forming carotid sinus (baroreceptor).

● In the posterior wall of carotid sinus lies the carotid body (chemoreceptor for O2 & CO2 concentration).

External Carotid artery● Arises from common carotid artery lateral to upper border of thyroid cartilage, and ends

within the parotid gland behind the neck of mandible into maxillary & superficial

temporal arteries.

● Ascends anteromedial, anterior, and lateral to internal carotid artery.

● Overlapped by sternomastoid muscle and crossed anteriorly by the posterior belly of

digastric, stylohyoid muscle & ligament and hypoglossal nerve.

● Within the parotid gland, the facial nerve and retromandibular vein are anterior to it.

● The styloid process, stylopharyngeus and styloglossus muscles, glossopharyngeal nerve

and pharyngeal branch of vagus lie behind it (between external & internal carotid

arteries).

● it branches are: 1. Superior thyroid . 2. Ascending pharyngeal. 3. Lingual 4. Facial 5. Occipital 6. Posterior auricular 7. maxillary 8. Superficial temporal

1. Superior Thyroid Artery: ● Descends to thyroid lobe accompanied by external laryngeal nerve. ● Gives infrahyoid, superior laryngeal, sternomastoid & cricothyroid arteries.

2. Ascending Pharyngeal Artery: ● Ascends on the lateral wall of pharynx. ● Gives branches to palatine tonsil and pharyngeal wall.

3. Lingual Artery: ● Ascends to the tongue passing deep to hyoglossus muscle. ● Gives sublingual, dorsal lingual and deep lingual arteries.

4. Fascial Artery: ● Ascends medially grooving submandibular gland. ● Crosses the lower border of body of mandible at the anterior border of masseter muscle where its pulsations are easily felt. ● Enters the face having a tortuous course, terminates as angular artery at the medial angle of orbit. ● Gives: ascending palatine, tonsilar, submandibular, submental branches in the neck, and inferior labial, superior labial and lateral nasal in the face.

5. Occipital Artery: ● Ascends to the scalp along the lower border of posterior belly of digastric muscle. ● Accompanies the greater occipital nerve. ● Gives muscular branches, stylomastoid artery and branches to posterior part of scalp.

6. Posterior Auricular Artery: ● Ascends behind the auricle and supplies auricle and scalp.

7. Maxillary Artery: ● Arises as terminal branch within the parotid gland behind the neck of mandible. ● Ascends into infratemporal fossa and then to pterygopalataine fossa where it terminates with the branches of pterygopalatine ganglion. ● Gives: deep auricular, anterior tympanic, inferior alveolar, middle meningeal & accessory middle meningeal, deep temporal, masseteric, pterygoid, buccal, superior alveolar, zygomatic, infraorbital, greater palatine, pharyngeal, sphenopalatine arteries and the artery of pterygoid canal.

8. Superficial Temporal Artery: ● Terminal branch arises within parotid gland and ascends to the side of scalp. ● Gives transverse facial, zygomatico-orbital, middle temporal arteries and breaks down into anterior and posterior branches to the scalp.

Internal Carotid Artery:

● Arises as terminal branch of common carotid artery.● Ascends to the base of skull and enters into cranium through carotid canal.● Gives no extra-cranial branches.● Its intracranial course and branches will be discussed in the neuro-anatomy module.

Subclavian Artery

● The right artery arises from brachiocephalic trunk behind the sternoclavicular joint.

● The left artery arises from arch of aorta and ascends lateral to trachea.

● The right & left arteries arch into the root of neck anterior to cervical pleura and over the superior surface of 1st rib.

● The corresponding subclavian vein is anterolateral to it.

● Continues as axillary artery at the outer border of 1st rib

● The scalenus anterior, phrenic nerve and vagus nerve lie anterior to it.

● The scalenus medius, right recurrent laryngeal nerve lie posterior to it.

● Divided by scalenus anterior into three parts:

I. First Part: medial to scalenus anterior and gives:

1. Vertebral Artery (gives muscular & spinal branches & forms basilar artery inside skull)

2. Internal Thoracic Artery (anterior intercostal arteries to upper 6 spaces, perforating branches, mammary branches, pericardiophrenic artery, musculophrenic and superior epigastric ateries.

3. Thyrocervical Trunk (gives transverse cervical artery, suprascapular artery & inferior thyroid artery) .

II. Second Part: posterior to scalenus anterior and gives costocervical trunk which divides into deep cervical artery and superior (highest) intercostal artery.

III. Third Part: lateral to scalenus anterior and gives no branches.

Veins of Head & Neck

Internal Jugular Vein

● Begins in the jugular foramen as a continuation of sigmoid sinus and ends into the corresponding brachiocephalic vein.

● Has superior bulb in the jugular foramen and inferior bulb near its termination.

● Descends in the carotid sheath lateral to internal carotid artery and then to the common carotid artery with the vagus nerve postero-intermediate.

● Related anteriorly to sternomastoid, sternohyoid, sternothyroid, superior belly of omohyoid.

● Posteriorly are the cervical transverse processes, prevertebral muscles, sympathetic trunk.

● Receives; inferior petrosal sinus, occipital vein, pharyngeal veins, facial vein, lingual vein, superior & middle thyroid veins.

External Jugular Vein

● Begins behind the angle of mandible by union of posterior auricular vein and posterior division of retromandibular vein. (The retromandibular vein id formed with in parotid gland by union of superficial temporal vein & maxillary vein. It divides into anterior & posterior divisions. The anterior division joins the facial vein forming common facial vein which opens into internal jugular vein. The posterior division units with posterior auricular vein to form external jugular vein)

● Descends superficial & in lower part of neck pierces the deep fascia to end into corresponding subclavian vein.

● It receives: posterior external jugular, transverse cervical vein, suprascapular vein, anterior jugular vein & some times, the occipital vein.

Anterior Jugular Vein:

● Formed in the superficial fascia of submental area and descends lateral to midline.● The two veins above sternum are connected by jugular arch.● It receives blood from skin & fascia, and ends into corresponding external jugular vein.

Subclavian Vein:

● The continuation of axillary vein at the outer border of 1st rib.

● Receives the external jugular vein.

● Joins the internal jugular vein behind sternoclavicular forming brachiocephalic vein.

Salivary Glands

Three pairs; parotid, submandibular and sublingual , located in the region of head & neck around oral cavity. They secret saliva into oral cavity via their ducts. Additional small salivary glands exist in the mucosa & submucosa of palate, mouth cavity and nasopharynx. The saliva contains water, electrolytes, mucus, amylase and IgA produced by the plasma cells of connective tissue. The IgA taken by secretory cells will be secreted combined to their product.

Parotid Gland

● The largest one located anterior and below the auricle on the ramus of mandible.

● Extends from external auditory meatus above to the upper part of the side of neck on the sternomastoid muscle.

● Has a fibrous capsule and a fascial sheath derived from the investing layer of deep fascia of neck.

● Its shape is irregular, wedged between the ramus of mandible, masseter anteriorly and mastoid process and sternomastoid posteriorly.

● The facial nerve passes within the gland and divides it into superficial and deep parts.

● The parotid duct (Stensen’s duct) emerges from the superficial part, crosses over masseter, pierces buccinator muscle and overlying fat & fascia to open into mouth vestibule opposite the 2nd

upper molar tooth.

● The parotid gland has 4 extensions or processes which include;

♣ glenoid process behind the temporomandibular joint.

♣ pterygoid process between medial pterygoid muscle and mandible.

♣ facial process over the masseter muscle.

♣ accessory parotid gland (detached part of the gland over the masseter).

● Strucures passing within the gland from superficial to deep are:

♣ Facial nerve and its terminal branches

♣ Retromandibular vein with its tributaries and divisions (maxillary and superficial temporal veins, anterior & posterior divisions)

♣ External carotid artery and its two terminal branches (maxillary & superficial temporal arteries).

♣ Also lying within the gland are the deep parotid lymph nodes.

Relations of Parotid Gland:

Superiorly: temporomandibular joint and external auditory meatus.

Superficially: parotid fascia, parotid lymph nodes & great auricular nerve.

Anteromedially: temporomandibular joint, ramus of mandible, masseter & medial pterygoid muscle

Posteromedially: mastoid process, sternomastoid, posterior belly of digastric and stylohyoid muscles, carotid sheath containing internal carotid artery, internal jugular vein & vagus nerve, and the facial, glossopharyngeal, accessory and hypoglossal nerves.

Nerve Supply of Parotid Gland:● The skin & fascial sheath of parotid gland are supplied by great auricular nerve from cervical plexus.

● Postganglionic parasympathetic nerves are derived from the otic ganglion and reach the gland via auriculotemporal nerve. The preganglionic parasympathetic nerves to otic ganglion is from lesser petrosal nerve of glossopharyngeal nerve.

● Postganglionic secretomotor sympathetic nerves are from the superior cervical sympathetic ganglion via plexus on external carotid artery. Preganglionic sympathetic fibers to superior cervical sympathetic ganglion are derived from lateral gray mater of upper four thoracic spinal segments.

Blood Supply & Lymphatic Drainage of Parotid Gland

Arteries: branches from external carotid, maxillary & superficial temporal arteries.

Veins: retromandibular vein.

Lymph drainage: parotid lymph nodes & deep cervical lymph nodes.

Submandibular Gland

● The 2nd largest salivary gland located in the neck, deep to the body of mandible (in the submandibular fossa), and separated from parotid gland by the stylomandibular ligament.

● Has fibrous capsule and invested by a sheath of fascia from investing deep fascia of neck.

● It consists of a large superficial part and a smaller deep part which are continuous with each other at the posterior border of mylohyoid muscle.

● The submandibular duct (Wharton’s duct) emerges from the deep part and runs anteriorly on hyoglossus muscle and then between sublingual gland and genioglossus muscle to open in the floor of mouth cavity proper by a small papilla at the side of the frenulum of tongue.

Relations of Superficial Part:

Anteriorly: anterior belly of digastric muscle.

Posteriorly: posterior belly of digastric and stylohyoid muscles.

Laterally: superiorly is the medial surface of body of mandible, while inferiorly are the investing deep fascia of neck, submandibular lymph nodes, platysma muscle, cervical branch of facial nerve and the facial vein. The facial artery indents the posterosuperior part of gland.

Medially: mylohyoid and hyoglossus muscles, deep part of submandibular gland, and the lingual and hypoglossal nerves.

Relations of Deep Part:

Anteriorly: sublingual gland.

Posteriorly: posterior belly of digastric and stylohyoid muscles.

Medially: hyoglossus and styloglossus muscles.

Laterally: superiorly is the body of mandible, inferiorly are the mylohyoid muscle & superficial part of gland.

Superiorly: lingual nerve, submandibular ganglion and mucus membrane of mouth.

Inferiorly: hypoglossal nerve.

Nerve Supply of Submandibular Gland

● Sensory nerves are derived from lingual nerve

● Postganglionic parasympathetic nerves are from submandibular ganglion via branches of lingual nerve. The preganglionic parasympathetic of submandibular ganglion are derived from the facial nerve via chorda tympani

● Postganglionic sympathetic nerves are from superior cervical sympathetic ganglion from the plexus on facial & lingual arteries.

Blood Supply & Lymph Drainage of Submandibular Gland

● Arteries: from facial & lingual arteries.

● Veins: into the corresponding veins.

● Lymph drainage: to submandibular and deep cervical lymph nodes.

Sublingual Gland

● The smallest pair of salivary glands located in the floor of mouth cavity under the tongue.

● It raises a transverse sublingual fold of mucosa in the floor mouth, and its ducts are 8-20 in number and open on the summit of sublingual papilla.

● A major sublingual duct (Bartholin duct) also joins the submandibular duct.

Relations of Sublingual Gland:

Anteriorly: the opposite sublingual gland.

Posteriorly: the deep part of submandibular gland

Laterally: body of mandible (sublingual fossa of mandible).

Medially: genioglossus, submandibular duct & lingual nerve

Superiorly: mucus membrane of mouth.

Inferiorly: mylohyoid muscle.

Blood Supply of Sublingual Gland:

Arteries: branches from facial & lingual arteries.

Veins: into the corresponding veins.

Lymph Drainage of Sublingual Gland:

Into the submandibular & deep cervical lymph nodes.

Nerve supply of Sublingual Gland:

● Sensory nerves are derived from lingual nerve.

● Postganglionic parasympathetic from submandibular ganglion via lingual nerve. The preganglionic to submansibular gaglion are from chorda tympani of facial nerve.

● Postganglionic sympathetic nerves are from superior cervical sympathetic ganglion via plexus on the arterial supply.

The Mouth Opening & Oral Cavity● The mouth opening (labial or oral fissure) lies between the two lips & leads into the oral cavity.

● The oral or buccal cavity is divided into a small vestibule and a larger oral cavity proper which are continuous with each other behind the last molar teeth when the jaws are closed.

The Vestibule

● The vestibule lies anterior to dental arch and bounded by the lips and cheeks.

● Each lip consists of skin, superficial fascia, orbicularis oris muscle & facial muscles at the angle of mouth and mucus membrane. The mucus membrane is moist lined by non-keratinized stratified squamous epithelium and contains labial mucus gland. In the middle of upper lip skin there is a depression called philtrum. The inner epithelium of each lip is reflected on the gums and in the middle, there is upper & lower labial frenulum (if tight and thick, they interfere with speech during childhood).

● Each cheek is formed by the skin, superficial fascia, buccal pad of fat, buccinator muscle and mucus membrane lined by non-keratinized stratified squamous epithelium and contains buccal mucus glands.

● The parotid duct pierces buccinator muscle and opens into the vestibule by a small papilla opposite 2nd upper molar tooth. This area is the site where the first vesicular eruption of measles is found (Koplic spot).

● The sensory nerve supply of upper lip is by infraorbital nerve of maxillary division of trigeminal nerve (5th cranial nerve) and the buccal nerve of mandibular division of trigeminal nerve. The mucus membrane of upper gum is supplied by superior alveolar branch of maxillary nerve.

● The sensory nerve supply of lower lip is by the mental and buccal nerves from mandibular division of trigeminal nerve. The mucus membrane of lower gum is supplied by inferior alveolar branch of mandibular nerve.

● The muscles of both lips are supplied by branches of facial nerve.

● The sensory supply of the skin and mucus membrane of cheeks is by buccal nerve from mandibular nerve. The motor supply is by facial nerve.

● The blood supply of lips and cheeks is by branches of facial and maxillary vessels, and their lymphatic vessels are drained into submandibular lymph nodes.

Mouth Cavity Proper

● Much larger than the vestibule, bounded anteriorly and laterally by dental arches of maxillae and mandible, superiorly (roof) by the palate, and inferiorly (floor) by the anterior two thirds of tongue & mucus membrane reflected from sides & inferior surface of tongue to lower jaw.

● Continuous posteriorly with oropharynx at oropharyngeal isthmus or isthmus of Fauces bounded by the two palatoglossal arches.

● On the under surface of tongue there is a median mucosal fold called frenulum of tongue (if thick and short it interferes with normal speech and requires surgical excision). Lateral to frenulum, the lingual artery, lingual nerve and deep lingual vein are located under mucosa in order from medial to lateral. The deep lingual vein can be seen through the illuminated mouth cavity. Just lateral to the vein there is a fold of mucosa called plica fimbriata.

● Lateral to the root of frenulum of tongue, there are two horizontal sublingual mucosal folds formed by sublingual glands. The multiple openings of sublingual ducts are located along the sublingual folds. The openings of submandibular ducts lie on the sides of the root of lingual frenulum.

● The mucosa of oral cavity proper is lined by non-keratinized stratified squamous epithelium and contains small salivary glands which open directly into oral cavity.

● The sensory nerve supply of mucus membrane of hard palate is by greater palatine and nasopalatine nerves from maxillary division of trigeminal nerve. The sensory nerve supply of soft palate is by lessor palatine branch of maxillary nerve & the glossopharyngeal nerve.

● The sensory nerve supply of floor of mouth is by lingual branch of mandibular division of trigeminal nerve.

● The arterial supply of palate is by the branches of maxillary artery (greater palatine, lesser palatine & sphenopalatine arteries), ascending palatine branch of facial artery & palatine branch of ascending pharyngeal artery. The floor of mouth cavity is supplied by branches of lingual artery.

● The venous drainage is into corresponding veins

● The lymphatic drainage is into the deep cervical nodes via submandibular lymph nodes.

The Teeth

● The deciduous teeth of childhood are 20; 4 incisors, 2 canines, and 4 molars in each jaw. The first eruption starts at 6 months usually in lower jaw and are completed by the age of 2 years.

● The permanent teeth are 32: 4 incisors, 2 canines, 4 premolars and 6 molars in each jaw. The last molar teeth are usually erupted by the age 17-30.

● Each permanent tooth consists of root and crown which join together at the cervix of tooth.

● The root or roots are embedded in their sockets in alveolar part of mandible and maxilla covered by mucus membrane (gingiva or gum). The root centrally has the pulp connected below with the root canal for nerves and vessels and immediately surrounded by hard dentin. External to dentine is much harder cementum which is bounded to alveolar bone by strong periodontal ligament .

● The crown projects from the root into mouth cavity and consists of inner dentin and outer enamel.

The Tongue● A mass of skeletal muscles covered by mucus membrane, located in oral cavity and oropharynx, and attached by its muscles to the styloid process of skull, mandible & hyoid bone. The right & left halves of tongue are connected together by a median fibrous septum.

● Divided by the V-shaped sulcus terminalis into the anterior 2/3 located in mouth cavity proper, and posterior 1/3 located in oropharynx. The apex of sulcus terminalis points posteriorly and has a pit representing the embryonic foramen cecum, the site where thyroglossal duct descends with thyroid gland from pharynx to the neck.

● The mucus membrane on the dorsum of anterior 2/3 of tongue is rough due to the projections of lamina propria under the epithelium forming many papillae.

● The mucous membrane on the dorsum of posterior 1/3 has many elevations produced by lymphatic follicles (lingual tonsil). The mucus membrane on the inferior surface of whole tongue is smooth and continuous with mucus membrane of lower gum and oropharynx.

● The epithelium covering the tongue is non-keratinized stratified squamous epithelium, below it lies the lamina propria. The lamina propria tightly binds the underlying muscles to surface epithelium. The submucosa contains several small mucus and serous glands whose ducts open on the surface of tongue. The skeletal muscles form the bulk of tongue and run in different directions.

● The papillae of the dorsum of anterior 2/3 of tongue are of three types; filliform, fungiform and circumvallate. The foliate papillae are not present in human tongue.

● The filliform papillae are elongated conical-shaped widespread on the dorsolateral areas, and contain no taste buds.

● The fungiform papillae are large mushroom-shaped with narrow stalk and contain taste buds.

● The circumvallate papillae are large circular-shaped, 7-11 in number located anterior to sulcus terminalis and contain taste buds. They are surrounded by circular groove which has the openings of the ducts of small lingual serous glands (Von Ebner’s glands) whose secretion help to dissolve the tastants which stimulate the taste buds. Also these glands secret lipase enzyme which prevents the formation of hydrophobic lipid substances on the surface of taste buds which interfere with action of taste buds and it also helps to digest fat in the stomach.

● Each taste bud is an onion-shaped collection of about 50-100 cells, connected to the surface through the taste pore. The cells rest on a basement membrane and consists of taste cells, supporting cells and basal proliferative cells. The apices of taste cells have microvilli projecting into the taste pore and have receptors for the tastants (sour and sweet tastants) or open ion channels (bitter and salt tastants) which eventually leads to depolarization of taste cells and the release of neurotransmitters. These events will stimulate special taste sensory nerve endings and the sensation is carried to special neurons in the brain.

Muscles of Tongue:

● Are intrinsic and extrinsic skeletal muscles.

● The intrinsic muscles run in different directions and include; vertical, transverse and longitudinal. They originate from tongue connective tissue and median fibrous septum and insert into the mucosa. They are supplied by hypoglossal nerve (12th cranial nerve), and help in changing the shape of tongue.

● The extrinsic muscles include; genioglossus, hyoglossus, styloglossus and palatoglossus. Their origin, insertion and action is shown in the following table:

Nerve Supply of Tongue:● All intrinsic and extrinsic muscles of tongue except palatoglossus are supplied by hypoglossal nerve. The palatoglossus is supplied by pharyngeal plexus (cranial accessory nerve).

● The sensory nerve supply is as follow:

Anterior 2/3: General sensations (touch, pressure, pain & temperature) by lingual nerve from V3 of trigeminal nerve. Special taste sensation excluding the taste sensations from the circumvallate papillae is by the chorda tympani branch of facial nerve.

Posterior 1/3: General sensation is by glossopharyngeal nerve and a small posterior area near epiglottis is by internal laryngeal branch of vagus nerve. Special taste sensation including the circumvallate taste buds is by glossopharyngeal nerve.

● The lingual glands are supplied by autonomic nerves. The postganglionic parasympathetic nerves is from submandibular ganglion via lingual nerve (preganglionic are from chorda tympani of facial nerve. The postganglionic sympathetic nerves is from superior cervical sympathetic ganglion along the arteries (preganglionic is from upper thoracic sympathetic ganglia) .

Movements of Tongue:

● The intrinsic muscles change the shape of tongue● Protrusion of tongue out of mouth is by genioglossus and hyoglossus of both sides.● Depression is by hyoglossus muscle● Retraction and elevation is by styloglossus and palatoglossus muscles.

Blood supply and Lymph Drainage of Tongue

● Arteries of tongue: lingual artery, tonsillar branch of facial artery, ascending pharyngeal artery.

● Veins of tongue: corresponding veins to internal jugular vein

● Lymph drainage: Anterior 2/3: from tip of tongue to submental lymph nodes from the rest to submandibular lymph nodes and upper deep cervical nodes (jugulodigastric) of both sides.

Posterior 1/3: upper deep cervical nodes on both sides, some vessels are drained posteriorly into retropharyngeal nodes.

The Palate

● It lies between nasal cavity and nasopharynx above and the oral cavity below. It consists of anterior hard palate and posterior soft palate.

● The hard palate is formed by palatine processes of maxillae and horizontal plates of palatine bones strictly covered by mucus membrane which has few small mucus glands. The mucus membrane is respiratory one on its upper surface while of oral type inferiorly

● The soft palate is a soft mass arises from the posterior border of hard palate and has a free posterior border which projects into the oropharynx with a small muscular projection at its middle called uvula.

● The soft palate consists of; mucus membrane, palatine aponeurosis, glands, muscles with nerves, blood and lymphatic vessels.

● The epithelium is respiratory on the upper surface while oral on lower surface.

● The mucosa and submucosa contains mucus and serous glands.

● The palatine aponeurosis is a sheet of dense fibrous tissue and is formed by the extension of the tendons of tensor palati muscles.

● The muscles of soft palate are; levator palati, tensor palati, palatoglossus, palatopharyngeus and musculus uvulae. Their attachment, nerve supply and action is shown in the following table:

Muscle Origin Insertion Action Nerve Supply

Tensor Veli PalatiniSpine of sphenoid & auditory tube

Form palatineaponeurosis

Tenses soft palateNerve to medial pterygoid from mandibular nerve

Levator Veli PlatiniPetrous part of temporal bone & auditory tube

Palatine aponeurosis Raises soft palatepharyngeal plexus

PalatoglossusPalatine aponeurosis

Side of tonguePulls root of tongue upward & backward, narrows oropharyngeal isthmus

pharyngeal plexus

PalatopharyngeusPalatine aponeurosis

Posterior border of thyroid cartilage

Elevates wall of pharynx pharyngeal plexus

Musculus UvulaePosterior border of hard palate

Mucus membrane of uvula

Elevates uvula pharyngeal plexus

Muscles of Soft Palate

Nerve Supply of Palate:● Sensory nerve supply of hard palate is by the lesser palatine,and nasopalatine branches of maxillary nerve, while that of soft palate is by branches of glossopharyngeal nerve.

● The motor supply of all palatine muscles except tensor palati is by pharyngeal plexus (from cranial accessory nerve via vagus). The tensor palati is supplied by nerve to medial pterygoid from mandibular nerve.

● The pharyngeal plexus lies on posterior pharyngeal wall and formed by: pharyngeal branch of vagus (its motor content is derived from cranial accessory nerve) pharyngeal branch of glossopharyngeal nerve pharyngeal branches of superior cervical sympathetic ganglion

Blood Supply of Palate:

Arteries: branches of maxillary artery (greater palatine, lesser palatine & sphenopalatine) ascending palatine branch of facial artery palatine branch of ascending pharyngeal artery

Veins: corresponding veins into maxillary, facial & pharyngeal veins

Lymph Drainage: into deep cervical lymph nodes.

The Pharynx

● Muscular tube lies behind oral, nasal and laryngeal cavities.

● 12-13 cm long extends from base of skull to the level of lower border of 6th cervical vertebra (lower border of cricoid cartilage) where it continues with esophagus.

● Its wall is formed by mucosa, submucosa, skeletal muscles and fibrous tissue. The mucosa epithelium is non-keratinized stratified squamous in oro- and laryngopharynx, while it is columnar ciliated in nasopharynx. The submucosa contains mucus glands and lymph follicles.

● The muscles of pharynx are skeletal muscles and include: superior, middle and inferior constrictors, cricopharyngeus, stylopharyngeus, palatopharyngeus and salpingopharyngeus. Their attachment, nerve supply and action is listed in the following table:

Muscles of Pharynx Origin Insertion Action Nerve Supply

Superior constrictor Medial pterygoid plate, pterygoid hamulus,

pterygomandibular raphe, posterior part of mylohyoid line

of mandlble

Pharyngeal tubercle of skull and pharyngeal

raphe

Swallowing Pharyngeal plexus

Middle constrictor Lower part of stylohyoid ligament, greater and lesser

cornu of hyoid bone

Pharyngeal raphe Swallowing Pharyngeal plexus

Inferior constrictor Thyroid and cricoid cartilages Pharyngeal raphe Swallowing Pharyngeal plexus, branches from

external laryngeal and recurrent

laryngeal nerves

Cricopharyngeus Lowest part of inferior constrictor

Closes the inlet of esophagus

Sphincter of the end of pharynx

Pharyngeal plexus, recurrent

laryngeal nerve

Stylopharyngeus Styloid process of skull Posterior border of thyroid cartilage

Elevates pharynx Glossopharyngeal nerve

Palatopharyngeus Palatine aponeurosis Posterior border of thyroid cartilage

Elevates pharynx Pharyngeal plexus

Salpingopharyngeus Catilage of Auditory tube Blends with muscles of pharynx

Elevates pharynx Pharyngeal plexus

Parts of Pharynx

Nasopharynx:

● The upper part of pharynx lies behind the nasal cavity and below the body of sphenoid and basilar part of occipital bone.

● It extends from the posterior nasal openings (choanae) to palatopharyngeal isthmus.

● The pharyngeal tonsil is a collection of lymphoid tissue in its upper posterior part.

● The auditory tube opening lies in its lateral wall and its posterior margin is raised by the tubal tonsil forming tubal ridge or elevation.

● The salpingopharyngeal mucosal fold contains salpingopharyngeal muscle and descends behind the tubal ridge. The pharyngeal recess is a depressed area behind the tubal ridge.

Oropharynx

● Lies behind the oral cavity and begins at the oropharyngeal isthmus bounded by the two palatoglossal arches.

● Its lateral wall has the palatglossal and palatopharyngeal arches which encircle the tonsillar fossa or sinus occupied by the tonsil.

● Its floor has three mucus folds between the tongue and epiglottis (one median glossoepiglottic fold and two lateral glossoepiglottic folds. Valeculla is the space between each lateral glossoepiglottic fold and median glossoepiglottic fold Laryngopharynx:

● Lies behind the larynx and it is connected anteriorly with the cavity of larynx through the inlet of larynx.

● Anteriorly and on each side of inlet of larynx, the laryngopharynx has a dead space called piriform recess or fossa which is the site for stagnation of food stuff & foreign bodies.

● Inferiorly, it is continuous with the esophagus.

Nerve Supply of Pharynx

Sensory supply: ● Nasopharynx by lesser & greater palatine branches of maxillary nerve ● Oropharynx and laryngopharynx by glossopharyngeal nerve ● A small areas around the inlet of larynx by internal laryngeal branch of vagus nerve.

Motor supply ● Glossopharyngeal nerve (stylopharyngeus muscle) ● Cranial accessory nerve via vagus (all other muscles of pharynx)

Autonomic supply: ● Postganglionic sympathetic fibers from superior cervical sympathetic ganglion along the arteries. ● Postganglionic parasympathetic from pterygopalatine ganglion via lesser & greater palatine nerve.

Blood Supply & Lymph Drainage of Pharynx

Arteries: ascending pharyngeal artery, ascending palatine branch of facial artery, branches of maxillary artery, branches of lingual arteryVeins: into the corresponding veins

Lymph Drainage: into deep cervical lymph nodes directly and via retropharyngeal and paratracheal lymph nodes.

The Esophagus

● 25 cm long muscular tube continues from lower end of pharynx at the lower border of cricoid cartilage opposite the body of 6th cervical vertebra.

● Descends in the neck (cervical part), superior and posterior mediastinum (thoracic part), pierces the right crus of diaphragm at the level of 10th thoracic vertebra to enter the abdomen and joins the cardiac end of stomach (abdominal part ~ 1.25cm).

Relations of Cervical Part

Posteriorly: the 6th & 7th cervical vertebrae and pre-vertebral muscles & fascia.

Anteriorly: the trachea & recurrent laryngeal nerve

Laterally: the thyroid gland, carotid sheath and its contents, and the thoracic duct on the left.

Relations of Thoracic Part:

Posteriorly: thoracic vertebrae & prevertebral muscles, thoracic duct, posterior vagal trunk (right vagus), azygos vein, descending thoracic aorta, and the right posterior intercostal arteries.

Anteriorly: trachea, left recurrent laryngeal nerve, left principle bronchus, left atrium and anterior vagal trunk (left vagus).

Laterally to Right: mediastinal pleura, lung, & azygos vein.

Laterally to Left: mediastinal pleura & lung, arch of aorta, left subclavian artery, and thoracic duct.

Relations of Abdominal Part:

Posteriorly: posterior vagal trunk & left crus of diaphragm.

Anteriorly: anterior vagal trunk & left lobe of liver.

Blood Supply of Esophagus

Cervical part: inferior thyroid artery & vein.Thoracic part: arterial supply from descending thoracic aorta & left gastric artery. venous drainage into azygos, hemiazygos & left gastric vein.Abdominal part: left gastric artery & vein.

Lymph Drainage of Esophagus

Cervical part: deep cervical lymph node.Thoracic part: mediastinal, left gastric and celiac lymph nodes.Abdominal part: left gastric and celiac lymph nodes.

Nerve Supply of Esophagus

Cervical part: recurrent laryngeal nerves & branches of middle cervical sympathetic ganglion.Thoracic part: esophageal plexus formed by branches of anterior & posterior vagal trunks and branches of thoracic sympathetic ganglia.Abdominal part: anterior & posterior gastric nerves of vagal trunks, and branches of thoracic sympathetic ganglia.

Thyroid Gland■ Brownish-red in clor, highly vascular and butterfly-shaped gland, located in the anterior part of lower neck.

■ Consists of the right and left lobes connected by a small median isthmus.

■ Has a fibrous capsule and is invested by the pretracheal layer of the deep cervical fascia, which moves the gland with swallowing.

■ Each thyroid lobe is conical in shape, extends from the oblique line of thyroid cartilage superiorly, to the level of fourth or sixth tracheal ring inferiorly.

■ Each lobe has three surfaces; antero-lateral, posterolateral, and medial.

■ Its anterolateral or superficial surface is covered by the sternothyroid, sternohyoid, superior belly of omohyoid, deep fascia, superficial fascia, platysma and the skin.

■ The medial surface is related to the larynx, trachea, esophagus, inferior constricter, cricothyroid, inferior thyroid artery, and the external and recurrent laryngeal nerves.

■ The posterolateral surface is related to carotid sheath containing common carotid artery, internal jugular vein and vagus nerve.

■ The superior and inferior parathyroid glands are embedded in the fascial sheath at the posterior border of the thyroid lobe.

■ The isthmus is small lies over the 2nd, 3rd and 4th tracheal rings, and is covered by the deep fascia, superficial fascia and skin.

■ Occasionally, a small conical projection from the left part of isthmus extends up as a pyramidal lobe which may be connected to hyoid bone by a fibrous cord called levator glandulae thyroidae.

■ Levator glandulae thyroidae represents the remains of thyroglossal duct which is the embryonic pathway for the descent of thyroid gland from the floor of primitive pharynx.

■ It is supplied by the superior thyroid arteries from the external carotid arteries and the inferior thyroid arteries from the thyrocervical trunks of the 1st part of subclavian arteries. Occasionally, a small single artery (thyroidae ima artery) ascends to the isthmus commonly arising from arch of aorta or brachiocephalic trunk. The thyroid gland receives minor arterial supply from tracheal and esophageal arteries.

■ Each lobe has superior, middle and inferior thyroid veins. The superior and middle veins open into the internal jugular vein, while the inferior thyroid vein usually joins its fellow on the trachea and usually drains into the left brachiocephalic vein.

■ The nerves are derived from the superior, middle and inferior cervical sympathetic ganglia.

■ Its lymphatic drainage is into the deep cervical lymph nodes.

Clinical Anatomy of ThyroidGland:■ The thyroid gland consists of thyroid follicles separated by the stroma and blood vessels.■ The cells of thyroid follicles synthesize thyroxine hormones (tri-iodothyronin, T3 and tetra-iodothyronin,T4), which are stored in follicular colloid. The parafollicular cells or C cells are located between the follicles and produce calcitonin. ■ Physiological or pathological enlargment of the thyroid gland is called goiter. During thyroid surgery, attention must be paid to the safety of the recurrent laryngeal nerves and parathyroid glands. ■ Overproduction of throxines in adult, results in hyperthyroidism, a condition manifested by incr-eased metabolic rate, anxiety, restlessness, sweating, tremor, increased appetite, heat intolerance and palpitation. ■ A special form of autoimmune thyrotoxicosis is called Grave’s disease, which is manifested by exophthalmus and peripheral osteoarthropathy. ■ Decreased production of throxines due to iodine deficiency, tumors, or post thyroidectomy, results in hypothyroidism or myxoedema, a condition manifested by lowerted metabolism, weakness, cold skin, slowness of thought, action and speech and edema. ■ Decreased production of thyroxines in children results in the retardation of growth, a condition called cretinism.

Parathyroid Gland ■ Small, yellowish-brown, oval organs, located in the fascial sheath of the thyroid gland at its posterior borders. ■ Include superior and inferior pairs. The superior parathyroid pair is derived from the fourth pharyngeal pouch, while the inferior pair is derived with the thymus from the third pouch. ■ The glands are formed of cords of chief cells, separated by the blood sinusoids, and secrete parathormone, which regulates the serum calcium level. The secretion of parathormone is regulated by the serum calcium level. ■ The blood vessels of the gland are derived from the superior and inferior thyroid vessels, and the lymph vessels are drained into deep cervical lymph nodes. ■ The nerve supply is derived from the superior and middle cervical sympathetic ganglia. ■ Overproduction of parathormone due to adenoma produces hypercalcemia with deposition of calcium in the body tissues are in the kidney tubules (renal stones). ■ Decreased production of parathormone due to infection, postthyroidectomy or tumor, results in hypocalcemia and tetany, a condition manifested by sever muscular spasm.

Cervical Sympathetic Trunk■ Continuation of thoracic trunk to the base of skull, and has three pairs of sympathetic ganglia; superior, middle and inferior.■ The superior ganglion is large, lies on longus coli muscle deep to prevertebral fascia, and represents the fused upper four cervical ganglia, the middle represents the fused 5th and 6tth ganglia and lies at the level of cricoid cartilage, and the inferior is the smallest and represents the fused 7th and 8th ganglia.■ The inferior ganglion may fuse with the 1st thoracic ganglion forming cervicothoracic or stellate ganglion.■ The cervical ganglia receive pregan-glionic fibers from the upper thoracic segments, which ascend through the sympathetic trunk. ■ The postganglionic fibers from the cervical ganglia enter the cervical spinal trunks via the grey rami communicantes, and distribute to the head, neck and upper limb regions through their ventral and dorsal rami.

Branches of superior ganglion: 1. postganglionic fibers from the superior cervical ganglia (internal carotid nerve), form plexuses around the internal carotid arteries, 2. Post ganglionic fibers extend to form plexuses around the common and external carotid arteries, which distribute with their branches to the head and neck region.

3. Communicating postganglionic fibers to the upper four cervical ventral rami,

4. Communicating postganglionic fibers to the glossopharyngeal, vagus and hypoglossal nerves via the jugular nerve.

5. Pharyngeal branches to pharyngeal plexus.

6. Superior cardiac branch to cardiac plexus in the thorax.

Branches of middle ganglion:1. Gray rami communicantes to 5th and 6th cervical spinal nerves.2. Branches to inferior thyroid artery.3. Middle cardiac branch to cardiac plexus in the thorax.4. Connecting loops to inferior cervical or stellate ganglion. One of these loops crosses anterior to subclavian artery and called ansa subclavia.

Branches of inferior ganglion:1. Gray rami communicantes to 7th and 8th cervical spinal nerves.2. Postganglionic branches to subclavian and vertebral arteries.3. Inferior cardiac branch to cardiac plexus in the thorax.

Orbital CavityPyramidal-shaped cavity formed by skull bones with an apex directed posterior & formed by optic canal and a quadrangular orbital opening facing anterior.

Walls of orbital cavity:

Roof: formed by orbital plate of frontal bone.

Lateral wall: formed by zygomatic bone & greater wing of sphenoid.

Floor: formed by the orbital surface of maxilla.

Medial wall: anteroposterior formed by frontal process of maxilla, lacrimal bone, orbital plate of ethmoid, orbital process of palatine bone & lesser wing of sphenoid.

Foramens & fissures of orbital cavity:

Optic canal: located between the roots of lesser wing of sphenoid & transmits optic nerve & its covering meninges, ophthalmic artery & central retinal vein.

Superior orbital fissure: located between the roof & lateral wall & transmits superior & inferior division of oculomotor nerve, abducent nerve, nasociliary, frontal & lacrimal branches of ophthalmic nerve, trochlear nerve, superior ophthalmic veins (occasionally inferior ophthalmic vein) .

Infrerior orbital fissure: located between lateral wall & floor and transmits infraorbital nerve & vessels, zygomatic nerve & vessels & inferior ophthalmic vein.

Infraorbital canal: lies in the floor of orbit & transmits corresponding nerve & vessels.

Opening of nasolacrimal duct: for nasolacrimal duct, located in the anterior part of medial wall and opens in the inferior meatus of nasal cavity.

Supraorbital foramen: transmits supraorbital nerves & vessels.

Zygomaticofacial & zygomaticotemporal foramens: transmit corresponding nerve & vessels.

Anterior ethmoidal foramen: transmits corresponding nerve & vessels

Contents of orbital cavity:

1. Eyeball

2. Ocular fascia & fat

3. Extraocular muscles (levator palpebrae superioris, 4 recti & 2 oblique)

4. Nerves (optic, oculomotor & ciliary ganglion, ophthalmic nerve & its branches (nasociliary, frontal & lacrimal), trochlear, abducent and infraorbital and zygomatic branches of

maxillary nerve

5. Ophthalmic artery & its branches

6. Veins (central retinal vein, superior & inferior ophthalmic veins)

7. Lacrimal gland & lacrimal apparatus

8. Eyelids & conjuctiva

The eyeball ♣ Located in the anterior part of orbital cavity, and separated from the orbital fat by fascial

sheath. ♣ The fascial sheath of eye ball is pierced by the tendons of extraocular muscles which

provides a tubular sheath around each of them. The fascial sheaths of medial & lateral recti are attached to the medial and lateral wall of orbit

forming medial & lateral check ligaments. The fascial sheath below the eyeball is thickened to form suspensory ligament of eyeball which

is attached to both check ligaments. These ligaments together with orbital fat suspend the eyeball in position.

♣ It is slightly oval in shape due to the anterior convexity of the cornea.

♣ Its wall is formed by: 1. outer fibrous layer formed by sclera and cornea

2. middle pigmented vascular layer called uveal tract consisting of choroid, ciliary body and iris

3. inner neural layer formed by the retina. The optic nerve arises from retina at the

optic disc and enters the middle cranial fossa through optic canal.

Outer Fibrous Layer:1. Sclera

♣ Opaque, white layer form 5/6 of outer fibrous layer of eyeball and continuous with the cornea at the corneo-scleral junction or limbus.

♣ The limbus contains canal of Schlemm which drains the aquous humour into the veins. Its closure increases intraocular pressure, a condition called glaucoma. If untreated, the increase in pressure will be reflected on vitreous humour and retina and results in blindness.

♣ It gives attachment to all extraocular muscles.

♣ Posteriorly, it is continuous with the dura mater surrounding the optic nerve and pierced 3 mm medial to posterior pole of eyeball by optic nerve and central retinal vessels. This part of sclera is the weakest and called lamina cribrosa which is also pierced by short and long ciliary nerves and posterior ciliary arteries.

♣ Immediately behind the equator of eyeball, the sclera is pierces by four to five veins called venae vorticosae, which drain blood from all parts of eyeball except the retina.

♣ The anterior ciliary arteries pierces the anterior part of sclera behind the sclero-corneal junction.

2. Cornea

♣ Avascular, transparent, slightly convex, covered by conjuctiva, and forms anterior one sixth (1/6) of the outer fibrous coat.

♣ Consists of stroma made of collagen fibers type I covered externally by stratified squamous epithelium and by simple squamous epithelium internally.

♣ Has no blood supply and it is nourished by diffusion from aqueous humour of anterior chamber.

♣ The cornea is immunologically inert and can be safely transplanted between individuals.

♣ Sever injuries to the cornea result in the corneal opacities which interfere with the normal vision.

Middle Layer (Uvea or Uveal Tract):

1. Choroid

♣ The choroid is a highly vascular and pigmented layer forming posterior part of middle layer.

♣ It is continuous anteriorly with the ciliary bodies at the ora serrata which is the anterior non-neural part of retina

♣ The external surface of the choroid is loosely attached to the sclera, while its internal surface is firmly attached to the pigmented layer of the retina.

♣ The choroid at optic disc continues with the arachnoid and pia maters around the optic nerve.

♣ The choroidal cells contain dark brown melanin pigments which absorb the light traversing the retina.

2. Ciliary body

♣ It lies between the choroid posteriorly & iris anteriorly and formed of ciliary ring, ciliary stroma & ciliary processes.

♣ The ciliary ring is the posterior part which has shallow grooves called ciliary striae

♣ The ciliary processes, which are connected to the margin of the lens by the suspensory ligament.

♣ The ciliary stroma lies between the two epithelial layers and consists of collagen fibers, numerous ciliary vessels and ciliary muscles. The anterior surface of the ciliary body is lined

by columnar cells, while its posterior surface is lined by cuboidal cells.

♣ The ciliary smooth muscles are located peripherally, and include abundant meridianal and fewer circular

types.

♣ The ciliary muscles are supplied by parasympathetic component of short ciliary nerves from ciliary ganglion,and change the shape of lense in accomodation reflex. Stimulation of myridianal muscle fibers relaxes the suspensory ligament and increaes the convexity of lens, while stimulation of circular muscles tenses the suspensory ligament & elongates the lens.

♣ The ciliary body also secrets aqueous humour.

3. Iris

♣ A colored diaphragm, suspended in the aqueous humor between the cornea and the lens, with its margin attached to the ciliary body.

♣ It has a central round opening called pupil which allows light to enter into the eye.

♣ The stroma of the iris consists of collagen fibers, fibroblasts, melanocytes, blood vessels and pupillary smooth muscles.

♣ It is lined posteriorly by double-layered, pigmented epithelium.

♣ The pupillary muscles consists of radially and circularly arranged fibers, which upon stimulation, change the size of the pupil.

♣ The radial muscles or dilator pupillae are supplied by the sympathetic nerves of superior cervical ganglion via short & long ciliary nerves. They dilate the pupil in the distant vision

and dim light.

♣ The circular muscles, or sphincter pupillae, are supplied by parasympathetic nerves of ciliary ganglion through short ciliary

nerves and they constrict the pupil in close vision and in response to bright light.

Retina

♣ The retina is the inner sensory vascular layer of eyeball, lies between the choroid and hyaloid membrane of vitreous humour.

♣ It extends from optic disc posteriorly to ora serrata anteriorly, and consists of six layers of nerve cells.

♣ The layers from outward inward include the pigmented cells, rods & cones, outer nuclear cells, inner nuclear cells and ganglionic cells.

♣ The axons of ganglionic cells form optic nerve which leaves the retina at the optic disc.

♣ The optic disc lies 3-4 mm medial to posterior pole of eye ball, and when examined by the ophthalmoscope appears as a round pink area from which retinal blood vessels radiate peripherally. It lacks the rods and cones, and forms the blind spot of the retina.

♣ The macula is the most sensitive area of retina containing only cones which produces sharpest vision. It is located lateral to optic disc at the posterior pole of eyeball. It has central depression called central fovea.

Interior of EyeballThe interior of the eyeball contains the lens, the anterior aqueous and posterior vitreous segments.

1. Lens

♣ Transparent, flexible, biconvex, avascular body, located between the iris and the vitreous body, and held in position by the suspensory ligaments of the ciliary body.

♣ Invested by elastic, transparent fibrous capsule, and consists of the lens epithelium and lens fibers.

♣ The epithelium is confined to anterior surface of lens and is made of a single thin layer of cuboidal cells.

♣ The fibers form the bulk of lens and are made of crystalline proteins.

♣ During ageing and in diabetes mellitus, the fibers are hardened and clumped due to inadequate nutrition, and the lens become opaque and the vision is distorted, a condition called cataract. Complete cataract is usually treated by surgical removal of the lens and implantation of an artificial lens.

2. Aqueous Segment

♣ It lies anterior to lens, filled with aqueous humor, and divided by the iris into anterior and posterior chambers.

♣ The anterior chamber lies between the cornea and iris, while the posterior chamber lies between the iris and the lens. The two chambers are continuous with each other through the pupil.

♣ The aqueous humor is a clear fluid, secreted by the ciliary body, and is absorbed into the veins at the corneoscleral junction by a minute canal called canal of Schlemm, or scleral sinus venosus.

♣ The aqueous humor provides nutrition to the cornea and lens, supports the structures, and produces the normal intraocular pressure (16 mm Hg). In glaucoma, obstruction to drainage of aqueous humor, or increase in the production of aqueous and leads to an increase of intraocular pressure which causes ocular pain and visual disturbances.

♣ Sever untreated cases of glaucoma usually end with loss of vision.

Vitreous Segment:

♣ It occupies most of the interior of the eyeball, lined by hyaloid membrane, and is filled by a clear vitreous humour.♣ Produced by certain retinal cells and possibly from non-pigmented cells of ciliary body, and unlike aqueous humour, it is not reproducible.

♣ The vitreous humor is colorless, transparent gel, consists of water, electrolytes, glycoproteins and few collagen fibers.

♣ A narrow hyaloid canal runs in the middle of vitreous segment from optic disc to posterior surface of the lens, and represents the remnant of embryonic hyaloid artery of the lens.

♣ It slightly contributes to magnifying power of eye, support the back of lens and assists in holding the pigmented layer against neural layer of retina.

Blood supply of eyeball

♣ The arterial supply of the eyeball with exception of retina is through the anterior & posterior ciliary branches of ophthalmic artery.

♣ The retina is supplied by central retinal artery arising from the ophthalmic artery in the optic canal.

♣ The venous drainage of retina is by central retinal vein which ends into cavernous sinus, while the other layers of eyeball are drained by venae verticosae drained by superior and inferior ophthalmic veins.

♣ The superior & inferior ophthalmic vein joins the cavernous sinus through the superior orbital fissure. The inferior ophthalmic vein also joins the pterygoid venous plexus through the inferior orbital fissure.

Nerve Supply of Eyeball

♣ The nerve supply of the eyeball except the retina, is by the long and short ciliary nerves.

♣ The long sensory nerves are branches of the nasociliary branch of the ophthalmic nerve, and convey sensory and postganglionic sympathetic fibers to the ciliary body, iris, sclera & cornea.

♣ The short ciliary nerves are branches of ciliary ganglion, and convey postganglionic parasympathetic, postganglionic sympathetic and sensory fibers to the ciliary body and the iris.

Muscles of Orbital Cavity

1. Levator palpebrae superioris

♣ Thin triangular muscle, lies above superior rectus with frontal nerve crossing its upper surface.

♣ Originates from the lesser wing of the sphenoid anterosuperior to optic canal, narrow posteriorly and wide anteriorly.

♣ Its aponeurosis splits into upper & lower lamellae which pierce the orbital septum and extends into upper eyelid undercover of orbicularis oculi.

♣ It inserts into the superior tarsus and the skin of the upper eye lid.

♣ The upper lamella is formed by skeletal muscle fibers supplied by superior division of oculomotor nerve.

♣ The lower lamella is formed by smooth muscle fibers (Muller muscle) and supplied by sympathetic nerves from superior cervical ganglion.

♣ It elevates the upper eye lid, and its paralysis results in ptosis.

2. Extraocular muscles

♣ They include four recti (superior, inferior, medial and lateral), and superior and inferior oblique muscles.

♣ The four recti are originated from a common tendinous ring which is attached to the margin of optic canal and bridges the medial end of superior orbital fissure.

♣ The tendinous ring contains ophthalmic artery, optic nerve & covering meninges, superior and inferior divisions of oculomotor nerve, nasociliary nerve and abducent nerve.

♣ The recti muscles insert into the sclera 6 mm behind the corneoscleral junction.

♣ The superior rectus is supplied by superior division of oculomotor nerve, the medial & inferior recti are supplied by inferior division of oculomotor nerve, and lateral rectus is supplied by abducent nerve.

♣ The superior oblique arises from the sphenoid bone above and medial to optic canal while inferior oblique arises from the anterior part of the floor of orbit. They insert into the sclera behind the transverse equator of eyeball. The superior oblique is supplied by trochlear nerve, while the inferior oblique is supplied by inferior division of oculomotor nerve.

♣ The medial rectus muscle moves the eyeball medially. The lateral rectus muscle moves the eyeball laterally. The superior rectus moves the eyeball upward while the inferior rectus moves the eyeball downward. The superior oblique rotates the eyeball downward when pulled laterally by the lateral rectus. The inferior oblique rotates the eyeball upward when pulled laterally by the lateral rectus.

Arteries of Orbital Cavity

Ophthalmic artery::

♣ Arises from internal carotid artery after it emerges from cavernous sinus, enters the orbital cavity via optic canal inferior to optic nerve.

♣ It continues forward lateral to optic nerve, cross anterior to optic nerve toward medial part of orbital cavity.

♣ It gives: 1. Central retinal artery

2. Lacrimal artery, 3. Posterior & anterior ciliary arteries

4. Supraorbital artery 5. Posterior ethmoidal artery 6. Anterior ethmoidal artery

Terminates dividing into: supratrochlear (7) & dorsal nasal arteries (8).

Veins of Orbital Cavities:

♣ The orbital cavity is drained by superior ophthalmic, inferior ophthalmic and central retinal veins.

♣ The superior and inferior ophthalmic veins drain all the structures in the orbital cavity except the retina.

♣ The superior ophthalmic vein terminates in the cavernous sinus through the superior orbital fissure, while the inferior ophthalmic vein terminates in the pterygoid venous plexus through inferior orbital fissure.

♣ The central retinal vein drains the retina and terminates in the corresponding cavernous sinus through the superior orbital fissure.

The Eyelids

♣ The upper & lower eyelids cover & protect the eyeball, and attach to superior & inferior orbital margins.

♣ They are separated by palpebral fissure and meet at the medial and lateral angles of the eye.

♣ Their free margins carry long hairs called eyelashes.

♣ The medial end of their free border has no hair and enlarge forming small lacrimal papilla. In the center of each lacrimal papilla is lacrimal punctum leading to corresponding lacrimal canaliculus.

♣ Each eyelid consists of thin skin, loose subcutaneous tissue, orbicularis oculi & levator palpebrae superioris, hard fibrous layer called tarsal plate & conjuctiva.

♣ The two tarsal plates are joined together and the angles of eye by medial & lateral palpebral ligaments. Superiorly are continuous with orbital septum.

♣ The upper tarsal plate gives attachment to the orbicularis oculi and levator palpebrae superioris, while the lower plate gives attachment to the lower fibers of the orbicularis oculi.

♣ The eyelids have three types of glands 1. Sebaceous glands of Zeis open into the eyelashes. 2. Ciliary glands of Moll which are modified sweat glands open between the eyelashes. 3. Tarsal glands or Meibomian glands which are modified sebaceous gland, secret oily substance via ducts open behind the eyelashes.

♣ The conjuctiva is thin mucus membrane covers the inner surface of the eyelids (palpebral conjuctiva) and the anterior surface of sclera and cornea (ocular conjuctiva). The site of reflection between ocular & palpebral conjuctivae is called fornix (superior & inferior fornices). When the eye is closed, the space between the palpebral and ocular conjuctivae, is called conjuctival sac.

Lacrimal Apparatus

♣ It consists of the lacrimal gland, lacrimal ducts, lacrimal puncta, lacrimal canaliculli, lacrimal sac and nasolacrimal duct.

♣ The lacrimal gland is serous compound tubuloacinar in form located in the superolateral part of orbital cavity.

♣ It consists of a larger orbital part and a smaller palbebral part continuous with each other at lateral border of levator papebrae superioris.

♣ The lacrimal ducts are 12 in number, pierce superior conjuctival fornix and open in the conjuctival sac.

♣ The lacrimal puncta are small openings at the medial ends of the free border of upper and lower eyelids. The lacrimal puncta lead into the lacrimal canaliculli which open in the lacrimal sac.

♣ The lacrimal sac is small, lies on the lacrimal bone and continues as the nasolacrimal duct.

♣ The nasolacrimal duct is 13 mm long and opens in the middle of inferior meatus of nasal cavity.

♣ The lacrimal fluid contains mucus, electrolytes, immunoglobulins and lysozymes, and it moists, lubricates and prortects the cornea.

♣ The lacrimal gland is supplied by the lacrimal branch of the ophthalmic artery, and its venous drainage is into the ophthalmic veins. The lymphatic vessels are drained into the parotid nodes.

♣ The sensory nerve supply is by the lacrimal branch of the ophthalmic nerve which also conveys postganglionic sympathetic nerves are derived from the superior cervical ganglion, and the postganglionic parasympathetic nerves are derived from the pterygopalatine ganglion.

The Ear The ear is the organ of hearing and equilibrium, consisting of external, middle and internal parts.

External earIt consists of the auricle and external auditorymeatus.

Auricle♣ The auricle is a fibrocartilagenous structure responsible for collection of sound waves and directing them into the external auditory meatus.

♣ It consists of elastic cartilages covered by the auricular muscles and skin. Its lower part (lobule) has no cartilage and consists of firm fibrous fatty tissue.

♣ The blood supply of the auricle is through the branches of the posterior auricular and superficial temporal vessels.

♣ The auricular muscles are supplied by branches of facial nerve (temporal & posterior auricular), while its sensory supply is by the lesser occipital, great auricular, auriculotemporal nerves, and the auricular branch of vagus.

♣ The lymphatic drainage is into the deep cervical nodes.

External Auditory (Acoustic) Meatus:

♣ Extends between the auricle & tympanic membrane (2.5 cm long from concha).

♣ Its lateral third is cartilagenous, while its medial two-thirds is osseous.

♣ It is lined by skin containing long hairs, sebaceous glands, and modified sweat glands called ceruminous glands. The ceruminous glands secret ear wax or cerumen.

♣ The medial end of the meatus is wider than the lateral end, and its anterior wall and floor are longer than the posterior wall and roof as the tympanic membrane is placed obliquely.

♣ The meatus in the adult forms an S-shaped curve directed at first forward, medially & slightly upward, then posteromedially, and lastly forward, medially and downward toward the

tympanic membrane. In infants and children, the meatus is shorter and straighter.

♣ During otoscopic examination, the external auditory meatus is straightened by pulling the auricle backward and upward in adults, while straight backward in children.

♣ The meatal arteries are derived from the posterior auricular, maxillary and superficial temporal branches of the external carotid arteries.

♣ The venous drainage is into the corresponding veins, and the lymphatic are drained into deep cervical nodes.

♣ The nerve supply is by the auriculotemporal branch of mandibular nerve and auricular branch of the vagus.

Tympanic Membrane (Eardrum)

♣ Oval, thin, semitransparent, obliquely placed membrane lying between external and middle ears.

♣ Its margin is thickened by a fibro-cartilagenous ring which is attached to the tympanic sulcus of tympanic part of temporal bone. The sulcus is deficient superiorly between the anterior and

posterior malleolar folds which extend from lateral process of malleus to the margin of tympanic membrane.

♣ The small triangular area of tympanic membrane between these malleolar folds forms flaccid

part or pars flaccida of tympanic membrane. The rest of tympanic membrane forms the pars

tensa.

♣ It is formed by thin layer of dens fibrous tissue covered externally by skin and internally by simple low columnar ciliated epithelium.

♣ The external surface of tympanic membrane is concave as it is pull by the attachment of the handle of malleus. The central point of maximum concavity is called umbo.

♣ During inspection of tympanic membrane, a zone of bright light reflects from a small triangular area below the tip of malleus, this triangle is called cone of light.

♣ The sound waves vibrate the tympanic membrane, which in turn transmits them to the middle ear ossicles via the malleus.

♣ The arterial supply is derived from the maxillary, occipital and posterior auricular arteries, while the venous drainage is into the external and internal jugular veins.

♣ The lymphatic drainage passes into the parotid and upper deep cervical nodes.

♣ The nerve supply is by auriclotemporal nerve, auricular branch of the vagus and tympanic branch of the glossopharyngeal nerve.

Middle Ear (Tympanic Cavity)

♣ The middle ear is about 1 cm, air-filled chamber, located in the petrous temporal bone, and extending between the tympanic membrane and the lateral wall of the inner ear.

♣ The middle ear cavity includes the tympanic cavity proper and the epitympanic recess.

♣ The tympanic cavity proper lies along and parallel to tympanic membrane, while the epitympanic recess is the part of middle ear cavity above and behind the tympanic membrane.

♣ The middle ear cavity has roof, floor and anterior, posterior, lateral and medial walls.

Roof or tegmental wall: is formed by a thin bone called tegmen tympani which separates the middle ear cavity from the middle cranial fossa.

Floor or jugular wall: is formed of a thin bone called jugular plate separating middle ear cavity from internal jugular vein.

Anterior or carotid wall: is formed superiorly by the semicanal of the tensor tympani, in the middle by the auditory or eustachian tube, and inferiorly by a plate of bone that separates the middle ear cavity from internal carotid artery. The eustachian tube, or pharyngotympanic tube is 5 cm long and connects the cavity of middle ear with nasopharynx. Its posterior third is made of bone, while its anterior two-thirds is made of cartilages. it serves to equalizes the pressure inside the middle ear cavity with that of external acoustic meatus.

Posterior or mastoid wall: consists of the aditus to the mastoid, antrum and pyramidal eminence. The aditus connects the middle ear cavity with the mastoid antrum. The pyramidal eminence has the tendon of stapedius muscle which extends in middle ear cavityto the neck of stapes. The mastoid antrum is 1 cm space in the pertrous temporal bone which is connected anteriorly with epitympanic recess of middle ear, and inferiorly with the mastoid air cells.

Lateral or tympanic wall: is formed by the tympanic membrane.

Medial wall: is formed by lateral wall of inner ear and has central elevation called promontory, the oval window or fenestra vestibuli, and the round window or fenestra tympani. The promontary is produced by the first turn of bony cochlea; the oval window is closed by the foot piece of stapes, while the round window is closed by the secondary tympanic membrane. Above and behind the promontary and oval window, there is a round elevation called prominence of facial canal, which represents the position of geniculate ganglion of facial nerve.

Contents of Middle EarThe middle ear contains air, three ossicles, two muscles, nerves and blood vessels.

1. Ossicles of middle ear:The ossicles are the malleus, stapes and incus.

Malleus: consists of head, neck, long crus (handle) and anterior and lateral processes. The head is located in the epitympanic recess of middle ear and articulates with the body of incus.

The neck is a constriction after the head. The long crus is attached to tympanic membrane and has the insertion of tensor tympani near its

root. The anterior process is attached to the anterior wall of middle ear by the anterior ligament.

The lateral process gives attachment to anterior and posterior malleolar folds of tympanic membrane

Incus: consists of the body, long crus and short crus. The body lies in the epitympanic recess and articulates with the head of malleus. The long crus articulates with the head of stapes. The short crus is attached to posterior wall of middle ear by the posterior ligament.

Stapes: consists of the head, neck, anterior & posterior limbs, and the footpiece or base. The head articulates with the long crus of the incus, while the foot piece is fitted in the oval window. The posterior surface of the neck gives attachment to the tendon of stapedius muscle.

2. Muscles of the middle ear:

♣ Tensor tympani arises from cartilagenous part of Eustachian tube and greater wing of sphenoid. It inserts into the root of the handle of malleus & supplied by a branch from the nerve to medial pterygoid which arises from the trunk of mandibular nerve. It protects the organ of Corti of inner ear by tensing the tympanic membrane when the ear is exposed to sudden intensive sounds.

♣ Stapedius arises from pyramidal eminence in the posterior wall of middle ear, and inserts into the neck of the stapes. It is supplied by the facial nerve, and it damps the excessive ossilation of the stapes. In the paralysis of the stapedius due to facial nerve injuries, there is an increased intensity of hearing, a condition called hyperacusia.

3. Nerves of middle ear:Include tympanic plexus, facial nerve and the chorda tympani.

The facial nerve lies within its bony canal in the posterior wall of middle ear and emerges from the stylomastoid foramen.

The chorda tympani arises from the facial nerve above the stylomastoid foramen, passes anterosuperiorly, deep to mucus membrane covering the upper medial surface of tympanic membrane, and exits through petrotympanic fissure in the anterior wall of middle ear to join the lingual nerve.

The tympanic plexus lies on the medial wall of middle ear, and is formed by the tympanic branch of glossopharyngeal nerve and caroticotympanic nerves from the internal carotid sympathetic plexus. The tympanic plexus supplies the tympanic cavity, mastoid antrum, mastoid air cells and the Eustachian tube.

Blood supplyof middle ear:♣ The arterial supply of middle ear is derived from branches of occipital artery, posterior auricular artery, maxillary artery, middle meningeal artery, ascending pharyngeal artery and internal carotid arteries.

♣ The veins of middle ear are drained into the pterygoid venous plexus and the superior petrosal sinus.

♣ The lymphatic vessels are drained into the parotid and deep cervical lymph nodes.

Internal EarThe inner ear lies in the petrous part of temporal bone and is connected with posterior cranial fossa through the internal auditory meatus. It consists of an outer osseous labyrinth and an inner membranous labyrinth, and has peripheral sensory receptors of hearing and equilibrium.

Osseous Labyrinth

♣ The osseous labyrinth consists of central vestibule, cochlea anteriorly and three semicircular canals posteriorly. It is filled with perilymph.

♣ The vestibule is the central, oval-shaped part and has the oval and round windows on its lateral wall. The oval window is closed by the foot piece of stapes while the round window is closed by secondary tympanic membrane. In the posterior wall of vestibule there is a minute opening of the aquiduct of vestibule, which is occupied by the membranous endolymphatic duct.

♣ The cochlea is a shell-like structure, located anterior to vestibule and consists of two and a half turns around a central axis called modiolus. A thin spiral lamina extends from the modiolus and divides the cochlear canal incompletely into an upper scala vestibuli and lower scala tympani. The scala vestibuli and scala tympani are continuous with each other at the apex of cochlea or helicotrema.

♣ The three semicircular canals (superior or anterior, posterior and lateral) lie posterosuperior to vestibule and each has a swelling called ampulla located at one site of their junction with vestibule. The semicircular canals are continuous with the vestibule through five openings, one of which is shared by the crus commune of the superior and posterior canals.

Membranous Labyrinth♣ The membranous labyrinth consists of cochlear duct, saccule, utricle and three semicircular ducts. It is filled with endolymph.

♣ The cochlear duct lies within the osseous cochlea, between scala vestibuli and scala tympani, filled with endolymph and contains the sensory organ of Corti. It is continuous with the saccule through a narrow ductus reuniens.

♣ The saccule is a small sac within the vestibule, connected with the cochlear duct by the ductus reuniens and with the utricle by the utriculosaccular duct.

♣ The utricle is the larger vestibular sac, connected with the semicircular ducts, and with the saccule by saculoutricular duct. The saculoutricular duct continues as ductus endolymphaticus which extends through the aquiducts of vestibule under dura mater of posterior surface of petrous bone as saccus endolymphaticus.

♣ The three semicircular ducts have distended ampullae and are continuous with the utricle by five openings, one of which is shared by the superior and posterior semicircular ducts.

♣ The wall of each ampulla contains special receptors called crista ampullaris, which consists of supporting and hair cells. The cilia of the hair cells project into a gel-like layer called cupula.

♣ The wall of utricle and saccule contains special receptors called macula which consists of supporting and hair cells. The cilia of the hair cells path in a gelatinous layer called cupula which is studded with tinny crystals of calcium carbonate called otoliths.

♣ The peripheral processes of vestibular nerve encircle the bases of hair cells of the maculae and ampullae which pass to their cell bodies located in the inferior and superior vestibular ganglia.

Organ of Corti and Mechanism of Hearing

♣ The organ of Corti baths in the endolymph-filled cochlear duct, and consists of pillar cells, inner and outer hair cells resting on a basement membrane.

♣ Above the cilia of hair cells, lies a gelatinous layer of glycoprotein called membrena tectoria.

♣ The afferent fibers of the cochlear nerve emerge from hairy cells and pass to spiral ganglion.

♣ The sound waves are transmitted through the external auditory meatus and ossilate the tympanic membrane and tympanic ossicles. The ossilations of the foot piece of the stapes are transmitted into the perilymph of cochlear canal, which in turn moves the basement membrane of the organ of Corti in the cochlear duct and stimulates the hair cells by the contact between their cilia and the membrena tectoria. The stimuli are then transmitted by the cochlear nerve to temporal cerebral cortex for final integration.

The Cranial Nerves

1. Olfactory Nerve♣ Purely sensory nerve classified as SVA.

♣ It arises from receptors of olfactory neurons located in the upper posterior part of nasal cavity.

♣ The olfactory neurons are bipolar cells with ciliated peripheral dendrites and long central processes forming olfactory filaments which pass through cribriform plate of ethmoid and ending in the olfactory bulb.

♣ The olfactory bulb consists mainly of large mitral cells with few small tufted & granular cells.

♣ The dendrites of mitral cells synapse with the unmyelinated olfactory fibers forming rounded areas called synaptic glomerulus. The tufted & granular cells synapse with mitral cells.

♣ The mitral cells also synapse with axons from contralateral olfactory bulb through the olfactory tract.

♣ Axons of ipsilateral mitral & tufted cells and few axons form contralateral olfactory bulb will form olfactory tract located in the olfactory sulcus on the orbital surface of frontal lobe.

♣ The olfactory tract proximal to anterior perforated substance divides into medial & lateral olfactory striae.

♣ The lateral olfactory stria terminates in the olfactory areas of temporal cerebral cortex which include periamygdaloid & prepiriform areas. These areas represent the primary olfactory cortex.

♣ The entorhinal area of hippocampus which is connected with primary olfactory cortex is considered as secondary olfactory cortex (area 28).

♣ The primary & secondary olfactory areas are responsible for appreciation of olfactory sensations.

♣ The olfactory pathway consists of two order neurons & has no connection with thalamus.

♣ The primary olfactory cortex has connections with brain centers which evoke emotional & autonomic responses to olfactory stimuli.

♣ Anosmia is loss of olfactory sensation.

♣ Bilateral temporary anosmia usually occurs in common cold & allergic rhinitis.

♣ Unilateral anosmia results from damage to olfactory nerve, bulb or tract.

♣ Unilateral lesion of cortical olfactory area usually has no impairment of olfactory sensation as the olfactory pathway from each nasal cavity is bilaterally presented in the cerebral cortex.

2. Optic Nerve

♣ Purely sensory nerve classified as SSA.

♣ It is formed by myelinated axons of ganglionic cells of retina which converge forming the optic disc located 3-4 mm to nasal side of center of retina.

♣ The macula is the thinnest part of retina located at the posterior pole of eyeball containing only cones and produces the sharpest vision.

♣ The myelin sheath of the axons is formed by oligodendrocytes.

♣ The optic nerve is covered by brain meninges starting at its exit from eyeball, so any increase in the intracranial pressure will affect the optic disc and vision.

♣ Each optic nerve convey fibers from nasal half of retina including the nasal half of macula, and fibers from temporal half of retina including the temporal half of macula.

♣ The nasal half of retina receive visual impulses from temporal half of visual field, while the temporal half of retina is responsible for nasal half of vision.

♣ The macula is responsible for central part of vision and when damaged causes central scotoma or blindness.

♣ The optic chiasma is the site where there is decussation of fibers originating from nasal halves of retina including the nasal halves of macula, while fibers originating from temporal halves including the temporal half of macula remain uncrossed and ipsilateral.

♣ Each optic tract arises from posterolateral aspect of optic chiasma and most of its fibers terminate synapsing with the lateral geniculate nucleus of thalamus. Few fibers will pass to superior colliculus & pretectal nucleus for light body reflex and light pupillary reflex. Few other fibers terminate in suprachiasmatic nucleus of hypothalamus.

♣ The optic radiation (geniculo-calcarine tract) begin from lateral geniculate nucleus and pass through retrolentiformic part of internal capsule ending in the visual cortex around calcarine sulcus of occipital lobe.

♣ In the binocular vision, the right and left fields of vision are projected on parts of both retinae.

♣ The image of an object in the left field of vision is projected on the nasal half of left retina and the temporal half of right retina.

♣ Due to decussation of fibers from nasal halves of retinae, the left field of vision is conducted by right optic tract to lateral geniculate body and then reflected on the right primary visual cortex.

♣ Therefore, the left visual cortex is responsible for interpretation of objects in right field of vision, and the right visual area interprets the left field of vision.

♣ The upper lip or wall of calcarine sulcus is responsible for lower field of vision (upper retinal quadrants) while the lower lip is responsible for upper field of vision (lower retinal quadrants).

♣ In the binocular vision, the right and left fields of vision are projected on parts of both retinae.

♣ The image of an object in the left field of vision is projected on the nasal half of left retina and the temporal half of right retina.

♣ Due to decussation of fibers from nasal halves of retinae, the left field of vision is conducted by right optic tract to lateral geniculate body and then reflected on the right primary visual cortex.

♣ Therefore, the left visual cortex is responsible for interpretation of objects in right field of vision, and the right visual area interprets the left field of vision.

♣ The upper lip or wall of calcarine sulcus is responsible for lower field of vision (upper retinal quadrants) while the lower lip is responsible for upper field of vision (lower retinal quadrants).

Lesions of Optic Pathway

Direct & Consensual Light Reflexes:♣ Direct light reflex means constriction of pupil in same eye illuminated with light, while consensual light reflex means constriction of both pupils when light is illuminated to either eye.

♣ Visual impulse is transmitted via optic nerve, chiasma and tract. From optic tract few fibers transmit the impulse to pretectal nucleus of midbrain. From pretectal nucleus fibers arise and ends into both parasympathetic nuclei of 3rd cranial nerve (Esinger- Westphal neucleus). Preganglionic parasympathetic fibers from each parasympathetic nucleus pass through oculomotor nerve which enters into orbital cavity, synapse with ciliary ganglion, and postganglionic fibers supply the constrictor pupillary muscles.

Accommodation Reflexe:

♣ While looking on a very near by object, the two eyes are converged inward by the two medial recti muscles, the lenses of both eye thickens by contraction of ciliary muscles, and the pupils constrict to concentrate light in the centers of lenses.

♣ The pathway of this reflex is: Light travels via optic nerves, chiasma & tracts , medial geniculate bodies and reach the visual cortex of both hemispheres. From each visual cortex fibers pass to frontal eye field.

From frontal eye field fibers descend through internal capsule to oculomotor nucleus which stimulate medial rectus muscle.

Few descending fibers pass to parasympathetic nucleus of oculomotor nerve resulting in stimulation of ciliary & pupillary muscles.

Conjunctival or Corneal Reflex

♣ Objects like insects or flying bodies when touch the conjuctiva covering the cornea both eyelids are reflexly closed (blinked).

♣ The pathway is: The touch sensation of conjuctiva is carried by ophthalmic division of trigeminal nerve to main sensory nucleus.

From sensory nucleus fibers pass to bilateral facial motor nuclei via medial longitudinal fasciculus which in turn stimulate the contraction of both orbicularis oculi muscles causing closure or blinking of eyes.

Visual body Reflex

♣ When viewing an object in the field or during scanning movements of the eyes and head while reading, the eyes & head are moved toward the stimulus.

♣ The pathway is: The visual stimulus pass via optic nerves, chiasma & tracts to superior colliculus. From superior colliculus the impulses pass through tectospinal tract to stimulate the cervical muscle, and other fibers ascend to bilateral motor nuclei of 3rd, 4th & 6th cranial nerve via medial longitudinal fasciculus for eye movement.

3. Oculomotor Nerve

♣ Purely motor, containing GSE & GVE

♣ Has general somatic nucleus and general visceral parasympathetic nucleus or Edinger-westphal nucleus located in the midbrain at the level of superior colliculus.

♣ The general somatic efferent fibers supply levator palpebrae superioris, medial rectus, inferior rectus, superior rectus & inferior oblique extrinsic muscles of eyeball.

♣ The general visceral efferent fibers are preganglionic parasympathetic which synapse in the ciliary ganglion of orbital cavity. The postganglionic fibers from ciliary ganglion supply smooth muscles of ciliary body & constrictor muscles of pupil via short ciliary nerves.

♣ Arises from motor and parasympathetic nuclei in the tegmentum of midbrain at the level of superior colliculus.

♣ It emerges from ventral surface of midbrain medial to crus cerebri and continues forward in the intervals where the free and attached borders of tentorium cerebelli are crossed.

♣ It continues in the lateral wall of cavernous sinus and divides into superior & inferior divisions which enter the orbital cavity through medial end of superior orbital fissure within

the common tendinous ring of orbit.

♣ The superior division supplies levator palpebrae superioris & superior rectus.

♣ The inferior division supplies the inferior rectus, medial rectus, inferior oblique.

♣ The nerve to inferior oblique gives communicating branches to ciliary ganglion which convey preganglionic parasympathetic branches to the ganglion.

♣ The preganglionic parasympathetic fibers synapse in the ciliary ganglion and continue as postganglionic fibers in the short ciliary nerves arising from the ganglion to supply the ciliary muscles and constrictor pupillary muscles of iris.

♣ Lower motor neuron lesion of oculomotor nerve results in ipsilateral lateral squint (strabismus) and mydriasis.

Ciliary Ganglion:

♣ A tiny collection of parasympathetic neurons, located in the orbital fat between the lateral rectus muscle and optic nerve.

♣ It receives preganglionic parasympathetic connection from inferior division of oculomotor nerve and traversed by postganglionic sympathetic, and sensory nerves of nasociliary nerve which together with postganglionic parasympathetic fibers pass in the short ciliary nerves of the ganglion.

4. Trochlear Nerve

♣ Arises from its motor nucleus in the tegmentum of the midbrain at the level of inferior colliculus.

♣ Emerges from dorsal surface of midbrain, crosses to opposite side, and winds around lateral border

of crus cerebri.

♣ It continues forward in the lateral wall of cavernous sinus below oculomotor nerve.

♣ It enters the orbital cavity through the superior orbital fissure and supplies superior oblique muscle.

♣ Lesion of the nucleus or the nerve before decussation results in contralateral paralysis of superior oblique

muscle, while damage of the nerve after decussations causes ipsilateral paralysis of superior oblique muscle.

5. Trigeminal Nerve

♣ Mixed sensory & motor nerve, its functional components are GSA & SVE.

♣ The GSA component is included in the three divisions: ophthalmic, maxillary & mandibular

♣ The SVE component is only distributed in the mandibular division which supplies the muscles of mastication, tensor palati & tensor tympani muscles.

♣ Its motor nucleus lies in the pons medial to main sensory nucleus.

♣ The general sensory nuclei include main sensory nucleus, spinal nucleus and mesencephalic nuclei

♣ The main sensory nucleus is located in the pons, the spinal trigeminal nucleus descends in medulla & upper cervical spinal segments, and the mesencephalic nucleus ascends in the midbrain.

♣ The sensory nuclei receive general sensations from the three division whose 1st order neuron are bipolar neurons of trigeminal ganglion.

♣ The 2nd order neuron of sensory nuclei ascends ipsilateral & contralateral via trigeminal lemniscus which terminates in VPM nucleus of thalamus.

♣ The 3rd order neuron ascends from VPM nucleus to lower part of postcentral gyrus via posterior limb of internal capsule.

♣ The sensory nuclei of trigeminal nerve are connected with motor nucleus of facial nerve for corneal or conjuctival reflex.

♣ Clinical examination of trigeminal nerve is conducted by testing movements of TMJ and examination of general sensation of forehead & face.

♣ It joins immediately the trigeminal ganglion in the middle cranial fossa, on the anterior surface of pertrous bone.

♣ The sensory root represents the short central branches of the axons of pseudounipolar neurons of trigeminal g anglion, while the peripheral long branches are distributed in ophthalmic, maxillary and mandibular divisions of the ganglion.

♣ The motor root continues below the ganglion and distribute only in the mandibular division.

A- Ophthalmic Division

♣ It is purely sensory, gives meningeal branch to dura mater and divides into the frontal, lacrimal and nasociliary branches which enter the orbital cavity through the superior orbital fissure.

♣ The frontal nerve runs forward above levator palpebrae superioris, divides into supratrochlear and supraorbital branches which supply frontal air sinus and the skin of forehead.

♣ The lacrimal nerve continues above the lateral rectus giving branches to lacrimal gland and continues to supply the skin of lateral part of upper eyelid. It receives a communicating branch from zygomaticotemporal nerve conveying postganglionic parasympathetic fibers from pterygopalatine ganglion to lacrimal gland.

♣ The nasociliary nerve enters the orbital cavity within the common tendinous ring between the two divisions of oculomotor nerve. It passes deep to superior rectus muscle & continues

forward to medial side crossing above the optic nerve & ophthalmic artery. It gives following branches:

1. long ciliary branches which accompany short ciliary nerves along the optic nerve, piercing the scelera and supply the iris, ciliary body and cornea.

2. communicating branches to ciliary ganglion which convey sensory & postganglionic sympathetic fibers.

3. posterior ethmoidal nerve which supplies ethmoidal and sphenoidal air sinuses.

4. anterior ethmoidal nerve supplies sphenoidal & ethmoidal air sinuses and continues in the nasal cavity giving internal and external nasal branches which supply lower part of nasal mucosa and the skin of nose.

5. infratrochlear nerve is the continuation of nasociliary nerve which supplies the skin of the medial side of eyelids & root of nose.

B- Maxillary nerve

♣ It is purely sensory, gives a meningeal branch before it leaves cranial cavity through foramen rotundum to enter the pterygopalatine fossa.

♣ It gives communicating sensory branches to pterygopalatine ganglion, and continues into infratemporal fosa via pterygomaxillary fissure.

♣ It gives zygomatic & posterior superior alveolar branches at the pterygomaxillary fissure and continues as infraorbital nerve.

♣ The zygomatic nerve enter the lateral wall of orbital cavity via inferior orbital fissure and divides into zygomaticotemporal & zygomaticofacial branches which respectively leave the orbit via corresponding foramens in the body of zygomatic bone to supply the skin of temple and skin over zygoma. The zygomaticotemporal nerve gives a communicating branch to lacrimal nerve which conducts postganglionic parasympathetic fibers to lacrimal gland originating from pterygopalatine ganglion.

♣ The infraorbital nerve in the infraorbital canal gives middle & anterior superior alveolar nerves and enters the floor of orbital cavity via inferior orbital fissure. It continues in its canal in the floor of orbit & emerges below the inferior orbital margin via infraorbital foramen. It gives palpebral branches to lower eyelid, nasal branches, and labial branches to the upper lip.

♣ The three superior alveolar nerves supply maxillary air sinus and maxilla.

Pterygopalatine ganglion (sphenopalatine ganglion)

♣ A collection of parasympathetic neurons, located in the pterygopalatine fossa, and connected to the maxillary nerve by two communicating branches.

♣ The preganglionic parasympathetic nerves are derived from facial nerve and reach the ganglion through the nerve of pterygoid canal.

♣ The nerve of ptyregoid canal is formed by greater petrosal nerve of facial nerve conveying preganglionic parasympathetic fibers and deep petrosal nerve conveying postganglionic sympathetic fibers derived from internal carotid plexus of superior cervical sympathetic ganlion.

♣ The preganglionic parasympathetic nerves synapse with the cells of the ganglion, and distribute as postganglionic fibers with the branches of the ganglion. They supply lacrimal gland and mucus glands of the nasal cavity, palate and nasopharynx

♣ The postganglionic sympathetic fibers traverse the ganglion and distribute with its branches.

♣ Branches of ganglion are:

1. orbital branches join zygomaticotemporal nerve which in turn conducts it to lacrimal gland, through its connection with the lacrimal nerve.

2. nasal branches include medial and lateral branches which supply the posterior part of the medial and lateral nasal wall.

3. nasopalatine nerve supplies the mucosa of the nasal septum and hard palate.

4. greater and lesser palatine nerves, which supply the nasal cavity, palate and the nasopharynx.

5. pharyngeal branches supply the part of nasopharynx at the opening of auditory tube.

C- Mandibular nerve

♣ Mixed motor and sensory nerve, emerges from the lower part of trigeminal ganglion, and leaves the cranial cavity through the foramen ovale.

♣ Deep in the infratemporal fossa, it gives the recurrent meningeal nerve which supplies dura mater of middle cranial fossa via foramen spinosum and nerves to medial pterygoid that suspend the otic ganglion in place and supply tensor tympani & tensor palati muscles.

The otic ganglion positionally is related to mandibular nerve but functionally it is connected to glossopharyngeal nerve.

♣ It divides into the anterior and posterior divisions.

♣ The anterior division gives the deep temporal nerves to temporalis, masseteric nerves to masseter, nerve to lateral pterygoid, and continues as the sensory buccal nerve that supply

the skin & mucus membrane of the cheek

♣ The posterior division is larger, and gives the auriculotemporal, lingual and the inferior alveolar nerves.

♣ The auriculotemporal nerve supplies the auricle, external auditory meatus, skin of the side of face & scalp. It conveys postganglionic parasympathetic fibers from otic ganglion to parotid gland.

6. Abducent Nerve

♣ Purely motor classified as GSE nerve.

♣ It arises from motor nucleus in the tegmentum of lower part of Pons, in the floor of fourth ventricle surrounded by facial nerve forming facial colliculus.

♣ It enters the orbital cavity through the superior orbital fissure within the common tendinous ring of the orbit & immediately enters the lateral rectus muscle.

♣ Its nucleus is located in floor of 4th ventricle of lower part of pons

♣ Its paralysis results in medial squint.

♣ Lesions of facial colliculus results in ipsilateral medial squint & facial palsy.

7. Facial Nerve

♣ Mixed nerve contains motor, sensory & parasympathetic components. Its components include SSE, SVA & GVE.

♣ The sensory & parasympatheticfibers are contained in nervous intermedius nerve of facial.

♣ Fibers of SSE component arises from motor nucleus located in the pons and supplies muscles of facial expression, stapedius, stylohyoid & posterior belly of digastric. Its upper part is bilaterally controlled by corticonuclear fibers, while its lower part only by contralateral corticonuclear fibers.

♣ Fibers of SVA component of taste sensations pass via geniculate ganglia in inner ear & terminate in the nucleus of tractus solitarius.

♣ Preganglionic parasympathetic fibers of GVA component arise from superior salivatory & lacrimal nuclei located in the pons which terminate peripherally in submandibular & pterygopalatine ganglia.

♣ Postganglionic fibers of submandibular ganglion supply sunmandibular, sublingual glands & glands of oral cavity.

♣ Postganglionic fibers of pterygopalatine ganglion supply lacrimal gland and glands of nasal cavity & nasopharynx.

♣ It has motor, sensory and parasympathetic components, which respectively, arise from the facial motor nucleus, nucleus solitarius, lacrimal and superior salivatory nucleus.

♣ The sensory and parasympathetic parts are present in the nervous intermedius root of facial nerve.

♣ The facial & vestibulocochlear nerves enter the inner ear through the internal auditory meatus.

♣ The geniculate ganglion of facial nerve is located in the lateral wall of the inner ear and receives special sensation of taste from anterior 2/3 of tongue via chorda tympani of facial nerve.

♣ The greater petrosal nerve arises in the inner ear at the geniculate ganglion and conveys preganglionic parasympathetic fibers to pterygopalatine ganglion.

♣ The facial nerve continues in the posterior wall of middle ear, gives a small branch to stapedius muscle, and just above the stylomastoid foramen, it gives the chorda tympani nerve.

♣ The chorda tympani emerge from the facial canal and pass anterosuperiorly along the upper medial surface of tympanic membrane. It leaves the anterior wall of the middle ear through the petrotympanic fissure to join the lingual nerve. It conveys special taste sensation from the anterior two-thirds of tongue, and provide preganglionic parasympathetic fibers to submanibular ganglion. The postganglionic parasympathetic fibers from the ganglion pass along the lingual nerve to supply the submandibular & sunlingual salivary glands, and the glands of oral cavity.

♣ The facial nerve leaves the skull through the stylomastoid foramen, and gives the posterior auricular nerve and the nerves to posterior belly of digastric and the stylohyoid muscles. The posterior auricular nerve supplies the auricular muscles and the occipital belly of occipitofrontalis.

♣ It then enters the deep part of parotid gland, divides into terminal branches which supply the muscles of facial expression. These terminal branches leave the superficial surface of parotid gland as the temporal, zygomatic, buccal, marginal mandibular and the cervical.

8. Vestibulocochlear Nerve

♣ Pure sensory nerve classified as SSA.

♣ Include cochlear & vestibular parts.

1. The cochlear nerve:

♣ Is formed by axons of bipolar cells of spiral ganglion located in the cochlea of inner ear.

♣ The peripheral processes arise from organ of corti located in cochlear duct. The fibers of cochlear nerve terminate in the ventral & dorsal cochlear nuclei located at pontomedullary junction.

♣ Majority of fibers of 2nd order neuron of cochlear nuclei decussate in trapezoid body ascend in contralateral lateral lemniscus, while few fibers remain ipsilateral ascending in ipsilateral lemniscus. Few ascending fibers in both lemnisci will be interrupted by synapses in nucleus of trapezoid body, superior olivary nucleus and nucleus of lateral lemniscus for collateral connection with other parts of brain.

♣ Majority of fibers of lateral leminsci end by synapse with neurons of inferior colliculus while other continue to medial geniculate nucleus of thalamus.

♣ Fibers relayed in inferior colliculus will continue also to medial geniculate nucleus.

♣ Fibers from medial geniculate nucleus continue as auditory radiation passing through sublentiformic part of internal capsule ending in the auditory cortex (areas 41 & 42).

♣ Lesions in one auditory cortex has no clinical manifestation since each cochlear nucleus is bilaterally presented.

♣ Lesion in cochlear nerve, spiral ganglion or organ of Corti produce complete deafness in ipsilateral ear.

2. Vestibular Nerve:

♣ Formed by axons of bipolar neurons of vestibular ganglion located in the inner ear. Its peripheral processes originate from the ampulla of semicircular canals, utricle & sacule of inner ear.

♣ The fibers of vestibular nerve terminate in the vestibular nuclear complex (medial, lateral, ventral & dorsal nuclei) located in the lateral part of floor of 4th ventricle at pontomedullary junction.

♣ Fibers from vestibular nuclei pass to ipsilateral cerebellar cortex via vestibulocerebellar tract through inferior cerebellar peduncle.

♣ Few fibers ascend to end in the 3rd, 4th & 6th cranial nerves nuclei , other ascend to the thalamus and then to cerebral cortex in lower part of postcentral gyrus.

♣ Lesions of vestibular pathway usually result in disturbance of balance and equilibrium.

9. Glossopharyngeal Nerve

♣ Sensory, motor & parasympasthetic nerve, its component are, SSE, SVA, GVA, GSA, GVE.

♣ Fibers of SSE supplies stylopharyngeus muscle and originate from nucleus ambiguus of medulla oblongata.

♣ Fibers of SVA convey taste sensation from posterior third of tongue & terminate in nucleus of tractus solitarius.

♣ Fibers of GVA convey general sensation from posterior third of tongue & pharynx to spinal nucleus of trigeminal nerve.

♣ Fibers of GSA convey sensation from carotid body (chemoreceptor) and carotid sinus (baroreceptors) terminate in spinal nucleus of trigeminal nerve.

♣ Fibers of GVE are preganglionic parasympathetic which arise from superior salivatory nucleus and synapse in otic ganglion. Postganglionic fibers supply parotid gland via auriculotemporal nerve.

♣ Leaves the posterior cranial fossa, with the vagus and accessory nerves, through the jugular foramen.

♣ Has superior and inferior ganglia located in the jugular canal which consist of pseudounipolar neurons whose peripheral axons transmit gustatory and general sensations from posterior third of tongue, and general sensory impulses from the oropharynx and soft palate.

♣ Gives following branches: 1. Tympanic nerve enters the middle ear and forms a plexus on the tympanic membrane.

2. Lesser petrosal nerve enters a canal in the anterior wall of the middle ear and conveys preganglionic paraympathetic to otic ganglion. It is joined by postganglionic sympathetic fibers from internal carotid plexus derived from superior cervical sympathetic ganglion. The postganglionic autonomic fibers of the otic ganglion pass to parotid gland along the auriculotemporal nerve .

3. Carotid nerves are usually two, receive contribution from vagus nerve and descend to supply the baroreceptors of carotid sinus and chemoreceptors of carotid body.

4. Pharyngeal branches with the pharyngeal branches of vagus and postganglionic sympathetic nerves of superior cervical sympathetic ganglion form the pharyngeal plexus on the lateral wall of the pharynx. It supplies the muscles and mucus membrane of the pharynx.

5. Tonsilar branches supply the soft palate, palatine tonsil and the oropharynx.

6. Muscular branches supply stylopharyngeus muscle.

10. Vagus Nerve

♣ Parasympathetic, motor & sensory nerve.

♣ Its functional components are SSE, SVA, GVA, GSA, GVE.

♣ Fibers of SSE component supply muscles of palate, pharynx & larynx which originate from nucleus ambiguus.

♣ Fibers of SVA component convey taste sensation from most posterior part of tongue originate from vagal ganglia & terminates in nucleus of tractus solitarius.

♣ Fibers of GVA convey visceral sensation from respiratory, digestive & urinary ducts which arise from neyrons of vagal ganglia & terminate in the nucleus of tractus solitarius.

♣ Fibers of GSA from auricle & external auditory meatus arise from vagal ganglia and terminate in spinal nucleus of trigeminal nerve.

♣ Fibers of GVE are preganglionic parasympathetic arise from dorsal vagal nucleus and distribute to the thoracic and abdominal viscera. They synapse in parasympathetic ganglia usually in the wall of viscera and postganglionic fibers supply their smooth muscles and glands.

♣ The vagus nerve within the jugular canal has superior and inferior ganglia, which consist of pseudounipolar neurons. The superior ganglion is concerned with the somatic sensations, while the inferior ganglion is concerned with the visceral sensations from the heart, respiratory and alimentary systems.

♣ In the lower part of jugular canal, the vagus is joined by the cranial root of accessory nerve, which distribute in the pharyngeal and laryngeal branches of vagus.

♣ Emerges into the neck below the base of skull through jugular foramen. It descends within carotid sheath posterior & intermediate between internal carotid artery and internal jugular vein. It continues in carotid sheath between common carotid artery & internal jugular vein, and enters the thorax crossing anterior to 1st part of subclavian artery. In the thorax, both vagi descend posterior to root of corresponding lung, and in the posterior mediastinum, the right vagus descend posterior to esophagus while left vagus anterior to esophagus and enter the abdomen through esophageal hiatus. In the abdomen the vagi nerve break into branches which join abdominal autonomic plexuses.

1- Branches within jugular canal, include: ♠ meningeal branch to the meninges of posterior cranial fossa. ♠ auricular branch to the auricle, external auditory meatus and the tympanic membrane.

2. Branches in the neck, include :

♠ Pharyngeal branches descend to the pharyngeal plexus, to supply the muscles and mucus membrane of pharynx.

♠ Nerves to carotid body accompany the branches of glossopharyngeal nerve to supply carotid body & sinus.

♠ Superior laryngeal nerve divides into the internal and external branches. The internal laryngeal branch supplies the mucus membrane of the larynx down to the vocal folds, and a small area of the most posterior part of the tongue, adjacent to the epiglottis. The external laryngeal branch supplies the cricothyroid and inferior constrictor muscles.

♠ Right recurrent laryngeal nerve arises at the root of the neck, anterior to the subclavian artery, and ascends behind the artery to reach the larynx between the trachea and esophagus. It supplies all intrinsic muscles of larynx except cricothyroid, and the mucus membrane below the vocal folds.

♠ Superior, middle and inferior cervical cardiac branches descend into the thorax to superficial and deep cardiac plexuses which supply the heart and great vessels.

3. Branches in the thorax, include:

♠ Cardiac branches pass to the deep cardiac plexus

♠ Left recurrent nerve arises below arch of aorta, and ascends behind the ligamentum arteriosum to reach the lower end of the larynx, between the trachea and esophagus.

♠ Anterior and posterior pulmonary branches forming anterior and posterior pulmonary plexuses on the anterior and posterior surfaces of the hilum of lung.

♠ Esophageal branches form a plexus around the esophagus which supply the esophagus and pericardium.

4- Branches in the abdomen, include:

♠ Gastric branches from the right and left vagi supply the anterior and posterior surfaces of the stomach.

♠ Celiac branches pass to celiac plexus on the celiac trunk of abdominal aorta which distribute to gastrointestinal tract and glands.

♠ Hepatic branches forming hepatic plexus of the liver.

♠ Renal branches pass to the renal plexus around the renal artery to supply the kidney.

♠ Branches to superior & inferior mesenteric plexuses which supply the intestine.

11. Accessory Nerve

♣ Classified as SSE, Purely motor arises by cranial and spinal roots.

♣ The cranial root arises from the nucleus ambiguus.

♣ The spinal root arises from the upper five cervical spinal segments, ascends through foramen magnum to join the

cranial root in the posterior cranial fossa.

♣ The cranial root joins the vagus nerve within jugular foramen nd distributes with pharyngeal and laryngeal branches of vagus.

♣ The spinal root of accessory nerve merges in the upper lateraL part of the neck to supplies sternocleidomastoid and trapezius.

12. Hypoglossal Nerves

♣ Purely motor (SSE) arising from long motor nucleus in the medulla oblongata.

♣ It leaves the posterior cranial fossa through the hypoglossal canal or anterior condylar canal.

♣ at the base of skull, it descends with 9th, 10th & 11th cranial nerves posterolateral to internal carotid artery, crosses anterior to both carotid arteries and passes on hyoglossus muscle below the lingual nerve and submandibular duct to enter into the tongue.

♣ It gives: 1. Meningeal branch supplies meninges of posteior cranial fossa which is derived from upper cervical ventral rami.

2. Nerves to geniohyoid and thyrohyoid containing fibers of C1

3. Superior root of ansa cervicalis containing fibers of C1 which joins the inferior root of ansa cervicalis forming the loop of ansa cervicalis in the anterior wall of carotid sheath anterior to the internal jugular vein and common carotid artery.

4. Muscular branches to all intrinsic & extrinsic muscles of tongue except palatoglossus.

♣ Unilateral damage of hypoglossal nerve results in atrophy of same side of tongue, and on protrusion of tongue, the tip deviates to affected side.

The Cervical Prevertebral Muscles1. Anterior Prevertebral Muscles:♣ Located deep in the neck, anterior to cervical vertebrae and covered by preveretebral fascia♣ They include;

Rectus capitis anterior:♣ Attached to atlas vertebra and occipital bone.♣ Supplied by ventral rami of C1 & C2.♣ Flexes the head forward at atlantoaxial joint.

Rectus capitis lateralis:♣ Attached to atlas vertebra & occipital bone.♣ Supplied by branches of ventral rami of C1 & C2 spinal nerves.♣ Flexes the head laterally at atlantoaxial joint.

Longus capitis:♣ Attached to occipital bone and transverse processes of cervical vertebrae.♣ Supplied by branches of ventral rami of C1, C2 & C3 spinal nerves.♣ Flexes the head forward at atlantoaxial joint.

Longus coli:

♣ Extends between the atlas and third thoracic vertebrae.♣ Supplied by branches of ventral rami of cervical spinal nerves. ♣ Flexes the head forward at atlantoaxial joint.

The Lateral Prevertebral Muscles:Splenius capitis:

♣ Attached to mastoid process and superior nuchal line superiorly and to the lower part of ligamentum nuchae and spines of 7th cervical & upper four thoracic vertebrae inferiorly.

♣ Supplied by dorsal rami of cervical nerves.

♣ It retracts the head (backward flexion).

Splenius cervicis:

♣ Attached to transverse process of upper three cervical vertebrae superiorly and to the spines of 3rd-6th thoracic vertebrae inferiorly.

♣ Supplied by dorsal rami of cervical nerves.

♣ It retracts the head (backward flexion).

Levator scapulae:

♣ Originates from transverse process of upper four cervical vertebrae and inserts into the upper part of medial border of scapula.

♣ Supplied by dorsal scapular nerve (C5 ventral ramus).

♣ It elevates the scapula.

Scalenus anterior:♣ An important landmark for studying the anatomy of the root of neck.

♣ Originates from 3rd-6th cervical transverse processes and inserts into scalene tubercle of 1st rib.

♣ Supplied by the ventral rami of C4, C5 & C6 spinal nerves.

♣ It elevates the 1st rib and bends the head laterally

♣ Has the phrenic nerve within the prevertebral fascia lying anterior and the 2nd part of subclavian artery lying posterior to it.

Scalenus medius:♣ Arises from transverse processes of all cervical vertebrae and inserts into superior surface of 1st rib.

♣ Supplied by ventral rami of C3-C8 spinal nerves.

♣ It elevates the 1st rib and bends the head laterally

Scalenus posterior:♣ Lies deep to scalenus medius, originates from the 4th-6th cervical transverse processes and inserts into the 2nd rib.

♣ Supplied by ventral rami of C6-C8 spinal nerves.

♣ It elevates the 2nd rib and bends the head laterally

Scalenus Minimis:A small muscle fibers which enforces the suprapleural membrane over the cervical pleura.

Muscles of the Back of Neck:Trapezius:♣ Large & triangular in shape♣ Originates from external occipital protuberance, ligamentum nuchae, 7th cervical spine and all thoracic spines.♣ Inserts into the lateral third of clavicle, acromion process and spine of scapula.♣ Supplied by spinal accessory nerve.♣ It moves the scapula.

Semispinalis Capitis:♣ Originates from the transverse processes of upper 6 thoracic and 7th cervical veertebrae.♣ Inserts into the occipital bone in the medial area between superior and inferior nuchal lines.♣ Supplied by dorsal rami of upper thoracic and lower cervical nerves.

♣ It extends the head at atlantoaxial joint.

Semispinalis Cervicis:♣ Originates from upper 6 thoracic transverse processes.♣ Inserts into the 2nd – 5th cervical spines.♣ Supplied by dorsal rami of upper thoracic and lower cervical nerves.

♣ It extends the head at atlantoaxial joint.

Muscles of Sub-Occipital Triangle:♣ They lies deep to semispinalis capitis, immediately below the scalp.

♣ They form the boundaries of suboccipital triangle as follows: ♠ Medially are rectus capitis posterior major and rectus capitis posterior minor ♠ Supero-laterally is the obliquus capitis superior ♠ Infero-laterally is the obliquus capitis inferior

♣ They are supplied by suboccipital nerve (dorsal ramus of C1 spinal nerve).

♣ The floor of triangle is formed by posterior atlanto-occipital membrane and posterior arch of atlas.

♣ The roof is formed by semispinalis capitis.

♣ The triangle contains: ♠ Suboccipital nerve (dorsal ramus of C1) ♠ Vertebral artery ♠ Suboccipital venous plexus

Joints of Head & Neck

1) Temporo-Mandibular Joint (TMJ):

♣ A synonial joint formed by articulation of head of mandible with mandibular fossa and articular tubercle of temporal bone.

♣ Its joint cavity is divided into superior and inferior parts by the articular disc.

♣ Its fibrous capsule is supported by the following ligaments:

♠ Temporomandibular ligament laterally ♠ Sphenomandibular ligament medially ♠ Stylomandibular ligament (weak).

♣ Supplied by branches from the auriculotemporal & masseteric nerves.

♣ Its movements include; elevation, depression, retraction, protraction & side to side movement.

2) Atlanto-Occipital Joints:

♣ An ellipsoid synovial joint formed by the articulation between superior articular facets of atlas and occipital condyles.

♣ Stable and fixed by strong capsule and ligaments.

♣ Allows slight flexion, extension and lateral flexion of head.

3) Median Atlanto-Axial Joint:

♣ Pivot synovial joint between the dens of axis and anterior arch of atlas.

♣ Allows rotation of head.

4) Lateral Atlanto-Axial Joints:Plane synovial joints between inferior articular facets of atlas and superior articular facets of axis.

5) Intervertebral Joints (Between 2nd -7th):

They are 14 joints for each vertebra include: ♠ Fibrous joints between the bodies formed by intervertebral discs (2 joints for each vertebra)

♠ Right & left upper & lower plane synovial joints between the bodies at the lateral margins of intervertebral disc (8 joints for each vertebra = four upper & four lower).

♠ Synovial joints formed by the superior & inferior articulating facets of each vertebra (4 joints for each vertebra).

Muscles of The Vertebral ColumnDivided into superficial, middle and deep group

I. Superficial Group: are muscles extending between the vertebral column and upper limbs, and include: trapezius, latissmus dorsi, levator scapulae, rhomboid major & minor.

II. Middle Group: extends between vertebral column and thoracic ribs and include serratus posterior superior, serratus posterior inferior & levator coastrum.

III. Deep Group: are further subdivided into:

1. Superficial Group or Errector Spinae Muscles: divided into lateral, intermediate and medial groups..

A- Lateral Group: iliocostalis lumborum, iliocostalis thoracis & ilicostalis cervicis

B- Intermediate Group: longissimus thoracis & longissimus cervicis

C- Medial Group: spinalis capitis, spinalis cervicis & spinalis thoracis

2. Middle group: semispinalis capitis, semispinalis cervicis, semispinalis thoracis, multifidus, rotators

3. Deep group: interspinales & intertransversarii

Blood Supply of Vertebral Column & Muscles of Back:

Arterial Supply:

♣ In Cervical Region: Vertebral artery Occipital rtery Deep cervical artery Ascending cervical artery from inferior thyroid artery

♣ Thoracic Region Posterior intercostal arteries

♣ Lumbar Region: Subcostal artery Lumbar arteries of abdominal aorta

♣ Sacral Region: Ilio-lumbar artery from internal iliac artery Lateral sacral arteries from internal iliac artery Median sacral artery of aorta

Venous Drainage:

♣ Internal venous plexuses inside vertebral canal external to dura mater .

♣ External vertebral venous plexuses along side the vertebrae which are connected with internal vertebral venous plexus.

♣ The internal vertebral venous plexus is connected with occipital sinus and basilar venous plexus through foramen magnum.

♣ The external vertebral venous plexus is connected with regional veins: - Vertebral, occipital & deep cervical veins in the cervical region - Posterior intercostal veins in thorcic region - Subcostal and lumbar veins in lumbar region - Iliolumbar, lateral sacral & median sacral veins in sacral region.