cranial bones

Cranial bones

Cranial bones made up of squamous part consist of roof of frontal bone, parietal bone and occipital bone and base; ethmoid, sphenoid and occipital bone.

1. Frontal bone

Forms forehead

Roofs of orbits (eye sockets).

At birth - frontal bone 2 parts separated by frontal sutures.

Disappear age of 6, frontal bone become united.

1. Vertical plate

(Front forhead)

2. Orbital plate

(Roof of orbit)

3. Supra orbital margin

(Above the orbit, eyebrow ridge)

Notch present for nerve and blood vessel pass through small hole.

2. Parietal bone

Form superior slide roof and part of back of skull.

3. Occipital bone

Forms posterior part and most base of cranial skull.

Base is large oval opening foramen Magnum, spinal cord passes through to join medulla oblongata.

Hypoglossal nerve pass.

4. Temporal bone

Situated at side and base of skull forms lateral side of cranium.

1. Squamous portion

Superior part and largest part of temporal bone.

Zygomatic process of temporal joint the temporal bone.

Zygomatic bone articulates with temporal bone, frontal bone, maxilla and sphenoid bones.

2. Petrous portion 

Part of temporal bone, forms the part of skull between sphenoid and occipital bone.

3. Tympanic Portion

Form wall of external auditory canal and parts of wall of tympanic cavity.

Involve transmission of sound wave.

4. Mastoid portion

Posterior part of temporal bone like bony structure.

Attachment to ear and muscle and neck opening for blood vessels.

5. Sphenoid bone

Butterfly shape

Bone lie at middle part of base of skull.

Articulate with all other cranial bone, holding them together.

It articulate anteriorly with frontal bone.

Laterally with temporal bone

Posteriorly with occipital bone.

Parts of sphenoid bone

1. Body corpus 

Cube shaped

Located between ethmoid and occipital bone

Contains sphenoidal sinus which drains into nasal cavity.

2. Lesser wings

Forms part of floor of cranium and posterior part of orbit of eye.

3. Greater wings

Extends from sphenoid body in lateral, superior and posterior direction.

Form lateral wall of skull just anterior to temporal bone.

4. Pterygoid processes

Jaw to move vertical and horizontal direction during mastication.

Form part of wall of nasal cavity.

6. Ethmoid bone

Anterior cranial bone located between eye.

It lies anterior to sphenoid and posterior to nasal bone.

Form part of anterior portion of cranial floor, medial wall of orbit, superior portion of nasal septum and most of side walls of nasal roof.

Parts of ethmoid bone

1. Cribriform plate

Form roof of nasal cavity.

Olfactory nerve pass nose to brain.

2. Median prependicular plate

Forms large part of vertical nasal septum between two nasal cavity.

3. 2 lateral masses or labyrinth

Form wall between nasal cavity and orbits.

Contains superior and middle conchae.