WINDSOR UNIVERSITYSCHOOL OF MEDICINE

Head and Neck

Dr. SREEKANTH THOTA

DEPARTMENT OF ANATOMY

Bones of the Skull• The skull bones are made up of external

and internal tables of compact bone separated by a layer of spongy bone called the diploe.

COMPONENT PARTS

• The skull has 22 bones, excluding the ossicles of the ear.

• Except for the mandible, which forms the lower jaw, the bones of the skull are attached to each other by sutures, are immobile, and form the cranium.

Subdivisons

• 1.The cranium can be subdivided into: an upper part the calvaria, which surrounds the cranial cavity containing the brain(Neurocranium).

2.Lower anterior part-the facial skeleton (viscerocranium).

The cranium consists of the following bones, two of which are paired

• Frontal bone: 1• Parietal bones: 2• Occipital bone: 1• Temporal bones: 2• Sphenoid bone: 1• Ethmoid bone: 1

• The facial bones consist of the following, two of which are single:

• Zygomatic bones: 2• Maxillae: 2• Nasal bones: 2• Lacrimal bones: 2• Vomer: 1• Palatine bones: 2• Inferior conchae: 2• Mandible: 1

Frankfort horizontal line(anatomical position of Cranium)

• Horizontal plane represented by a line between Upper rim of the external auditory canal( auricular point), to the lower rim of the orbit( infraorbital point).

• FHL divides the head into upper and lower halves.

External Views of the Skull

• Anterior View of the Skull(Norma frontalis)

The anterior view of the skull includes the forehead superiorly, and, inferiorly, the orbits, the nasal region, the part of the face between the orbit and the lower jaw

Foramen of Anterior view

• 1. Supra-orbital foramen: Supra-orbital nerve and vessels.

• 2. Infra-orbital foramen: Infra-orbital nerve and vessels.

• 3. Mental foramen: Mental nerve and vessels

Superior view of the skull(Norma verticalis)

• Parietal foramen: Emissary veins

Bregma and Lambda

Posterior view of the skull(Norma occipitalis)

Downloaded from: StudentConsult (on 10 December 2006 10:40 AM)

© 2005 Elsevier

Lateral view of skull(norma lateralis)

• Zygomaticofacial foramen: Zygomaticofacial nerve

Downloaded from: StudentConsult (on 10 December 2006 10:40 AM)

© 2005 Elsevier

Fracture of the Pterion

A hard blow to the side of the head may fracture the thin bones forming the pterion, producing a rupture of the anterior branch of the middle meningeal artery crossing the pterion

Inferior view of the skull.

Foramen

• 1. Incisive fossa• 2. Greater and lesser palatine foramina• 3.Jugular foramen• 4.Carotid canal • 5.Stylomastoid foramen• 6.Foramen magnum

Skull

Cranial fossa

Internal Surface of the Cranial Base

• The internal surface of the cranial base has three large depressions that lie at different levels: the anterior, middle, and posterior cranial fossae .

Anterior cranial fossa

Foramen of Anterior cranial fossa

• 1. Cribriform plate:olfactory nerves (CN-I)• 2. Foramen cecum: occasional small emissary vein from nasal

mucosa to superior sagittal sinus.• 3. Anterior and posterior ethmoidal foramina: anterior and

posterior ethmoidal nerves, arteries, and veins.

Middle cranial fossa-

Foramen of Middle cranial fossa

1. Optic canal: optic nerve (CN II), ophthalmic artery.

2.Superior orbital fissure: oculomotor (CN III),

trochlear (CN IV), and abducens (CN VI) nerves; ophthalmic division of trigeminal nerve (CN V1) and ophthalmic veins.

3.  Foramen rotundum:  Maxillary nerve

• 4. Foramen ovale: Mandibular nerve, the accessory meningeal artery, and the lesser petrosal nerve.

• 5. Foramen spinosum: middle meningeal artery.

Posterior cranial fossa

Foramen of posterior cranial fossa

• Foramen magnum: medulla, the ascending portions of the spinal accessory nerve (XI), and the vertebral arteries.

• Internal acoustic meatus:facial (VII) and vestibulocochlear (VIII) cranial nerves

• Jugular foramen: internal jugular vein (actually begins here), the glossopharyngeal (IX), the vagus (X) and the accessory (XI) nerves.

• Anterior condylar (hypoglossal) canal:

hypoglossal (XII) nerve.

Fractures of the CalvariaA depressed skull fracture is a break in a cranial bone (or "crushed" portion of skull) with depression of the bone in toward the brain.A compound fracture involves a break in, or loss of, skin and splintering of the bone.

Contrecoup (counterblow) fracture

• No fracture occurs at the point of impact, but one occurs on the opposite side of the cranium.

When a moving object impacts the stationary head, coup injuries are typical, while contrecoup injuries are produced when the moving head strikes a stationary object

Fractures to the Maxilla and associated bones

• Le Fort I Fracture = Horizontal Fracture • Le Fort II Fracture = Pyramidal Fracture • Le Fort III Fractures = Craniofacial

Separation