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Osteology of facial skeleton By Dr. Kalpajyoti Bhattacharjee Dept of oral pathology

Osteology of facial skeleton

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Page 1: Osteology of facial skeleton

Osteology of facial skeleton

ByDr. Kalpajyoti Bhattacharjee

Dept of oral pathology

Page 2: Osteology of facial skeleton

CONTENTS

• Introduction• Classification• Skull• Calvarium- paired and unpaired bones• Norma ventricalis• Norma occipitalis• Norma lateralis• Norma frontalis• Norma basalis• Interior of the skull• Facial skeletons

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INTRODUCTION

• Bone is the hard part of the body providing framework to it

• Bone acts as levers for muscles and therefore help in the movements of the body

• Bone provides protection to the visceral organs like brain, lungs and heart

• Bone is the site of blood formation• Plays an important role in the immune

responses of body• Store house of calcium and phosphorus

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• Study of bones-osteology• There are 206 bones in our body• Skull has 22 bones• Skull is the skeleton of head• Cranium- skull minus mandible• Calvaria is upper part of cranium also called

brain box• Facial skeleton is skull minus calvarium

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22 bones join to form the skull 8 pairs and 6 individuals Divided into neurocranium and viscerocranium Sometimes sutural bones present

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CLASSIFICATION

According to shapeLong bones ( eg: humerus, radius) Short bones (eg: carpal and tarsal bones)Flat bones (eg: vault of the skull, ribs )Irregular bones (eg: Vertebra, hip bone )Pneumatic bones (eg: maxilla, sphenoid )Sesamoid bones (eg: patella)

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Developmental classification Intramembranous or mesenchymal ossification.

eg: bones of the vault of skull and facial bones Intracartilaginous or endochondral ossification.

eg: bones of limbs, vertebral column and thoracic cage.

Membrano-cartilaginous bones. eg: clavicle, mandible.

Microscopic structure Mature bone. Immature bone

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Neurocranium Viscerocranium

The neurocranium covers the brain

The viscerocranium comprises the facial bones

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SKULL• Cranium: Consists of 8 bones

– (1) Frontal Bone– (2) Temporal Bones– (2) Parietal Bones– (1) Occipital Bone– (1) Sphenoid Bone– (1) Ethmoid Bone

• Face: Consists of 14 bones– (2) Maxilla– (2) Zygomatic bones– (2) Lacrimal bones– (2) Palatine bones– (2) Nasal bones– (2) Nasal conchae– (1) Vomer– (1) Mandible

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CALVARIUM

• The bones which constitute the calvaria or brain case are

• Unpaired bones a.Frontal bone b.Occipital bone c.Sphenoid bone d.Ethmoid bone• Paired bones- a.Parietal, b.Temporal

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NORMA VERTICALIS

• Oval in shape• Wider posteriorly than anteriorly.• Bones seen in norma verticalis:1) upper part of frontal bone anteriorly.2) uppermost part of occipital bone posteriorly.3) A parietal bone on each side.

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NORMA VERTICALIS

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Sutures seen are:

• Coronal suture: placed between the frontal bone and the 2 parietal bone.

• Sagittal suture: placed in the median place between the 2 parietal bone.

• Lambdoid suture: posteriorly between the occipital and the 2 parietal bone.

• Metopic (latin forehead) suture: occasionally present in about 3-8% individuals. Lies in the median plane. Separates 2 half of frontal bone and fuses at the 6 yrs of age.

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• Other features are:Vertex- highest point on saggital sutureBregma- meeting point between the coronal

and sagittal sutures.Lambda- meeting point between sagittal and

lambdiod sutures.Obelion- point on sagittal suture between two

parietal foramina

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PARIETAL BONES• The main bone on the side

of the skull.

• It articulates (joins) with the other parietal bone in the midline (top of the head), with the frontal bone in front of it, with the occipital bone behind it, and with the sphenoid and temporal bones lower down on the side of the skull.

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Clinical anatomyFrontanelles are sites of

growth of skull, permitting growth of brain and pulps to determine age.

If frontanelles fuse early- brain growth stunted, and child will be less intelligent.

Anterior frontenelle: bulging- increased

intracranial pressure. depressed- decreased

intracranial pressure

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NORMA OCCIPITALIS

• Convex upward and on each side , flattened below.

• Bones seen: • 1) posterior part of parietal bones, above.• 2)Upper part of squamous part of the occipital

bone below,• 3)mastoid part of the temporal bone on each

side.

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• Sutures seen are:1)Lambdoid suture2)Occipitomastoid suture3)parietomastoid suture4)Posterior part of saggital suture.

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OCCIPITAL BONE

• From the Latin, meaning the part of the head opposite the front.

• It occupies the posterior and inferior part of the skull.

• The occipital bone articulates (joins) with the parietal and temporal bones of the skull, the sphenoid bone in front of it, and the first cervical vertebra (the atlas) beneath it

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• Landmarks:– Foramen magnum: large hole, allowing

passage of the spinal cord– External occipital protuberance (EOP):

prominent projection on back of occiput– Nuchal lines: a superior and inferior line

running laterally from the midline, serve as a point of muscle attachment

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Foramen magnum

Wider posterior a. Lowest part of medulla oblongatab. Three meninges

Subarachanoid space a. Spinal accessory nervesb. Vertebral arteriesc. Sympathetic plexusd. Post spinal arteriese. Ant spinal arteries

Narrow anterior part a. Apical ligament of densb. Vertical band of cruciate ligamentc. Membrana tectoria

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NORMA FRONTALIS

• Roughly oval in outline, being wider above than below.

• Bones seen are:1)frontal bone.2)right and left maxillae form the upper jaw.3)right and left nasal bones.4)zygomatic bones5) mandible.

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• Sutures seen are1)internasal2)frontonasal3)nasomaxillary4)lacrimomaxillary5)frontomaxillary6)intermaxillary7)zygomaticomaxillary8)zygomaticofrontal

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FRONTAL BONE

• The large bone that makes up the forehead and supplies the upper edge and roof of the orbit (eye socket).

• The frontal bone articulates (comes together) with a number of other bones including the parietal, nasal, ethmoid, maxillary, and zygomatic bones.

• Landmarks:– Squama: flat portion that forms the forehead

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– Supraorbital margin: ridge under the eyebrow, forming the upper part of the orbit (eye socket)

– Supraorbital foramen: small hole within supraorbital margin for blood vessels and nerves

– Frontal sinuses: hollow spaces behind the squama, act as sound chambers to give the voice resonance.

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Clinical anatomy

Nasal bone is the most commonly fractured bone of the face.

Mandible and parietal eminence are next bone to be fractured.

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NORMA LATERALIS

• Bones seen are:1)frontal2)parietal3)occipital4)temporal5)sphenoid6)zygomatic7)mandible8)maxilla9)nasal

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• A large irregular bone situated at the base and side of the skull.

• The temporal bone is connected with the mandible (the jaw bone) via the temporomandibular (TM) joint.

• The temporal bone is formed of three parts

(squamous, tympanic and petrous) that are distinct at birth but then fuse. The petrous portion of the temporal bone contains the structures of the inner ear.

TEMPORAL BONE

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• Landmarks:– Squama: flat portion of the temporal bone

forming the anterior and superior part of the temple

– Zygomatic process: process forming part of the cheek.

– Petrous portion: internal, forming part of the floor of the cranium. Contains the ear canal and internal ear structures.

– Mandibular fossa: socket between squama and petrous portion, articulates with the condyle of the mandible (TMJ)

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– External auditory meatus: opening to the ear canal

– Mastoid process: bony prominence behind the external auditory meatus

– Styloid process: looks like an elephant’s tusk located between the mastoid process and the jaw. Acts as a point of attachment for muscles and ligaments.

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Clinical anatomyPterion is the thin part of the skull. In roadside accidents, the anterior division of middle

meningeal artery may be ruptured, leading to clot formation between the skull bone and durameter or extradural haemorrhage. The clot compresses the motor area of the brain leading to paralysis of the opposite site.

The clot must be sucked out at the earliest by trephining.

The head must be protected by a helmet.

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NORMA BASALIS

• Divided arbitrarily into- o anterior o middle o and posterior parts.

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• A prominent, irregular, wedge-shaped bone at the base of the skull. The sphenoid bone has been called the "keystone" of the cranial floor since it is in contact with all of the other cranial bones.

• Sphenoid bone resemble a bat with outstretched wings.

• Comprises: a body in the centre two lesser wings from the anterior part two greater wings from the lateral part two pterygoid processes.

SPHENOID BONE

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• Landmarks– Greater wings: large lateral projections of bone

that help to form the lateral border of the skull– Lesser wings: smaller lateral projections of

bone above the greater wings– Pterygoid processes: two long downward

projections from the greater wings that act as a point of muscle attachment.

– Sella turcica: known as the Turkish Saddle which cradles the pituitary gland.

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ETHMOID BONE• An irregularly shaped, bone that provides the floor of

the front part of the skull and the roof of the nasal cavity.

• The ethmoid consists of two masses of thin plates enclosing air cells and looks like a sieve.

• Landmarks:– Lateral masses: form most of the wall between

the nasal cavity and the orbits– Perpendicular plate: forms the superior portion of

the nasal septum– Cribiform plate: forms the roof of the nasal cavity

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– Olfactory foramina: small holes within the cribiform plate for passage of the first cranial nerve (for smell)

– Crista galli: upward extension of bone above the cribiform plate, acts as an anchoring point for one of the coverings of the brain.

– Nasal concha (turbinates): two scroll-shaped projections with a mucus membrane on either side of the nasal septum. Function to cause air turbulence and trap inhaled particles.

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Clinical anatomy

• Fracture of cribriform plate of ethmoid with tearing off of the meninges may tear the olfactory nerve rootlets. In such cases, CSF may drip from the nasal cavity. It is called CSF rhinorrhoea.

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Interior of the skull

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Anterior caranial fossa

Foramen caecum Emissary veins to nasal cavity

Olfactory foramina in cribriform plate

Olfactory nerves [I]

Optic canal Optic nerve [II]; ophthalmic artery

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Mid cranial fossa

Superior orbital fissure Oculomotor nerve [III]; trochlear nerve [IV]; ophthalmic division of the trigeminal nerve [V1]; abducent nerve [VI]; ophthalmic veins

Foramen rotundum Maxillary division of the trigeminal nerve [V2]

Foramen ovale Mandibular division of the trigeminal nerve [V3]; lesser petrosal nerve, accesory meningeal, emissary veins

Foramen spinosum Middle meningeal artery

Hiatus for the greater petrosal nerve

Greater petrosal nerve

Hiatus for the lesser petrosal nerve

Lesser petrosal nerve

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Posterior cranial fossa

Internal acoustic meatus Facial nerve [VII]; vestibulocochlear nerve [VIII]; labyrinthine artery

Jugular foramen Glossopharyngeal nerve [IX]; vagus nerve [X]; accessory nerve [XI]; inferior petrosal sinus, sigmoid sinus (forming internal jugular vein), meningeal branch of asce pharyng &occipital artery

Hypoglossal canal Hypoglossal nerve [XII]; meningeal branch of the ascending pharyngeal artery

Condylar canal Emissary vein

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ORBIT

Pyramidal bony cavities, situated one on each side

of the root of the nose.

They provide sockets for rotatory movements of

the eyeballs

Protection of eye

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Orbital complexBony recess that holds the eyeSeven bones

Frontal boneLacrimal bonesPalatine bonesZygomatic bonesEthmoidSphenoidMaxilla

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medial wall: frontal

process, lacrimal bone and

part of ethmoid

lateral wall: sphenoid,

zygomatic

floor: maxillary, zygomatic

pos: sphenoid + superior

orbital fissure

top: frontal bone

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Clinical anatomy

• Weakness and paralysis of a muscle causes squint or strabismus, which may be concomitant or paralytic.

• Nystagmus is characterized by involuntary, rhythmical oscillatory movement of the eyes.

• Optic neuritis is characterized by pain in and behind the eyes on ocular movements and on pressure.

• Hypertension causes atheromatous changes in the arteries of the eyes.

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FACIAL SKELETON

• Facial skeleton is composed of following bones A.Paired bones a.Maxilla b.Zygomatic bones c.Nasal bones d.Lacrimal bones e.Palatine bones f.Nasal conchae B. Unpaired bones a.Mandible b.Vomer

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MAXILLA

• The largest bones of the face, except for the mandible and formed by their union, the whole of the upper jaw.

• They hold the upper teeth, and connect on the left and right to the zygomatic bones (cheek bones).

• Each assists in forming of face, nose, mouth, orbit, infratemporal and pterygopalatine fossae.

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• Each maxilla has a body and 4 processes:1)frontal2)zygomatic3)alveolar4)palatine

• Maxilla ossifies in membrane from 3 centers- one for the maxillary proper and 2 for incisivum or premaxilla.

• Center for maxillary proper appears above the canine fossa during 6th week of IUL and 2 premaxilla – main above the incisive fossa during the 7th week of IUL and 2nd one appears at ventral margin of nasal septum during 10th week.

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• Landmarks:– Infra Orbital foramen: hole below the orbit,

for blood vessels and nerves – Alveolar process: arch of the maxilla

containing the upper teeth– Palatine process: horizontal projection of the

maxilla forming the anterior ¾ of the hard palate.

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AGE CHANGES• At birth: Transverse and anterioposterior diameter > vertical diameter Frontal process- well marked Body consists of a little more than the alveolar process. Tooth sockets reaching to the floor of the orbit Maxillary sinus is rudimentary.• In the adult: Vertical diameter due to development of alveolar process

and increase in size of the sinus.• In the old: The bone reverts to infantile condition. Height reduced

due to absorption of the alveolar process.

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MAXILLARY SINUS

• Also called antrum of highmore

• It is pyramidal in shape with base towards the nasal

cavity and apex towards the zygomatic processes

• It is the largest paranasal sinus and commonly

involved in inflammation process (maxillary

sinusitis)

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Clinical anatomy

• Infection of a sinus is known as sinusitis.• The maxillary sinus is most commonly

involved.• Carcinoma of maxillary sinus arises from the

mucosal lining.• Caldwell-luc operation is done as treatment.

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MAXILLARY FRACTURES

• Unilateral fracture of maxilla usually involves its alveolar process

• Bilateral maxillary fractures can be classified into Lefort I, Lefort II, Lefort III fractures

• Lefort I (Guerins fracture)-it is a horizontal fracture along the floor of the nose and below the zygomatic bone

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• Lefort II (in this the fracture line passes through orbits then runs medial to and below the zygomatic bones towards the alveolar margins

• Lefort III (In this fracture the fracture line runs through the nasal bones and orbits above the zygomatic bone. This is also called craniofacial dysjunction)

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LACRIMAL BONE Smallest and most fragile

bone of the face, is situated at the front part of the Medial of the orbit.

Contains: a)lacrimal sac and b)naso-lacrimal duct.

BORDERS: Anterior- frontal process Posterior- orbital plate of

ethmoid Superior- frontal bone Inferior- maxilla

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ZYGOMATIC BONE• Commonly referred to as the cheekbone. • It is situated at the upper

and lateral part of the Face.• It forms the prominence of

the cheek. FORMS: a) floor and lateral

wall of the orbit b) walls of temporal and infraorbital fossae.

PROCESSES: 1) FRONTAL AND 2) TEMPORAL

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NASAL BONE• 2 small oblong bones• Forms bridge of the

nose

BORDERS:• Superior- frontal bone• Inferior- lateral nasal

cartilage• Medial- opposite nasal

bone• Lateral- frontal process

of maxilla.

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Clinical anatomy

• Common cold or rhinitis is the most common infection of the nose

• Paranasal air sinuses may get infected from nose.

• Little’s area on the septum is a common site of bleeding from the nose or epistaxis.

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VOMER One of the unpaired facial bones of the skull. Located in the

midsagittal line, and touches the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones.

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NASAL CONCHAE

• Nasal conchae are curved bony projections directed downward and medially.

• 3 conchae are found: Inferior concha – independent bone. Middle concha- projection from middle surface of

ethmoidal labyrinth. Superior concha- projection from middle surface of

ethmoidal labyrinth and the smallest one.

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PALATAL BONE• 2 L-shaped bones• Posterior part of nasal cavity.Forms:1) the lateral wall and floor of

the nasal cavity, 2) the roof of the mouth3)floor of the orbit 4)Parts of pterygopalatine fossa3 processes:-pyramidal-orbital-sphenoidal

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MANDIBLE

• Largest and strongest bone of the face. • Develops from 1st pharyngeal arch.• Forms the lower jaw and holds the lower teeth in

place. • Landmarks:

– Body: curved horizontal portion of the mandible– Rami: two upward projections of bone that are

perpendicular to the body of the mandible.– Angle of the mandible: angle formed where the

body meets the ramus

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– Condylar process: a condyle on the posterior portion of the ramus that articulates with the mandibular fossa of the temporal bone.

– Coronoid process: a sharp projection of bone on the anterior portion of the ramus that acts as a point of muscle attachment.

– Alveolar process: arch of bone containing the lower teeth

– Mental foramen: small hole on the side of the body for blood vessels and nerves.

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BODY OF MANDIBLE

• External surface a.Symphysis menti b.Mental protruberance c.Mental tubercles d.Mental foramen e.Incisive fossa f.Oblique line• Internal surface a.Mylohyoid line b.Submandibular fossa c.Sublingual fossa d.Genial tubercles

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Clinical anatomy• The mandible is mostly

fractured at the canine socket where it is weak. Involvement of the IAN in the callus may cause neuralgic pain, which may be referred to the areas of distribution of the buccal and auriculotemporal nerves.

• Next common fracture areas are- angle and neck of the mandible.

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AGE CHANGES IN MANDIBLE

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• The body of the bone is a mere shell,

• The mandibular canal is of large size, and runs near the lower border of the bone;

• The mental foramen opens beneath the socket of the deciduous molar tooth.

• The angle is obtuse (140°), condyloid portion is nearly in line with the body.

• The coronoid process is of comparatively large size, and projects above the level of the condyle.

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Two segments of the bone become joined at the symphysis.

Increased growth of the body & the alveolar part behind the mental foramen

The mandibular canal, is situated just above the level of the mylohyoid line.

The mental foramen occupies the position usual to it in the adult.

The angle becomes less obtuse, 110°.

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OLD AGE Bone reduced in size. The alveolar process is resorbed.

The chief part of the bone is below the oblique line.

The mandibular canal & mental foramen is close to the alveolar border.

The ramus is oblique in direction, the angle measures about 140°

Neck of the condyle is more or less bent backward.

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REFERENCES

Cunningham’s Manual Of Practical Anatomy:

G.J.Romanes 15th Edition

Text book of Human Osteology: Inderbir Singh 1st Edition

Human Anatomy Regional and Applied: B.D.CHAURASIA

4th Edition

Kumar GS, Orban’s oral histology & embryology, 12th ed

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