Skull Flashcards
Is the skull made of one bone?
No, separate bones
What is the skull divided into?
Cranium
Face
From what are the facial bones suspended?
Front of cranial bones
What does the facial skeleton form?
Orbits
Nasal cavity
Lower jaw
What are the two parts of the cranium?
Upper = vault Lower = floor/base of skull
What does the vault contain?
Brain
Meninges
Cranial nerves and vessels
Describe the bone composition of the vault
External and internal table of compact bone
In between is layer of spongy bone = diploe
How are separate bones united in the skull?
United at series of immobile joints called sutures
What is the coronal suture?
In the coronal plane
Frontal bone anteriorly unites with parietal bones behind
What is the sagittal suture?
In the sagittal plane
Right and left parietal bones unite
What is the lambdoid suture?
In the coronal plane
Parietal bones unite with occipital bone
What is the pterion?
H shaped suture where four cranial bones meet
Bones particularly thin here
What are the four cranial bones that unite at the pterion?
Frontal
Parietal
Sphenoid
Temporal
What is directly deep to the pterion?
Middle meningeal artery
Grooves internal aspect of pterion
What does the middle meningeal artery supply?
Meninges and cranial bones
What are the two parts of the frontal bone?
Vertical part forms forehead
Horizontal/orbital plate forms roof of orbit
At what point does the front bone turn 90 degrees?
At supraorbital margin
Describe the parietal bones
Flat
Relatively rectangular
Molded to brain contour
Describe the occipital bone
Flat
Molded to shape of brain posteriorly
What is the midline project of the occipital bone called?
External occipital protuberance
Describe the squamous part of the temporal bone
Flat
Molded to lateral aspect of brain
What are the four processes of the temporal bone?
Zygomatic
Styloid
Mastoid
Petrous
Describe the zygomatic process
Extends anteriorly
Articulates with zygoma
Creates zygomatic arch
What is the zygoma?
Cheek bone
Describe the styloid process
Sharp spike of bone Extends inferiorly Deeply placed Gives attachment to muscles with stylo in their names - midline structures - Muscles of tongue - Muscles of pharynx
Describe the mastoid process
Extends posteroinferiorly
Thick, chunky, and superficially placed
Gives attachment to sternoclydomastoid muscle and others
Full of mastoid air cells
Describe the petrous process
Internal
Thick pyramidal shape
Projects inwards to cranial vault
Forms part of cranial floor
Describe the sphenoid bone
Like bat with outstretched wings In middle of floor Made of three parts - Body - Lesser wing - Greater wing - Two small legs
Describe the body of the sphenoid bone
Not solid piece of bone
Pituitary gland sits in cavity
Describe the wings of the sphenoid bone
Flip out and up
Flipped up part form small part of lateral aspect of cranium
Part of pterion
What is the slit between the two wings of the sphenoid bone?
Superior orbital fissure
What does the superior orbital fissure do?
Separates wing into small anterosuperior part = lesser wing, and large posteroinferior part = greater wing
What are the two legs of the sphenoid bone called?
Pterygoid plates
Are the pterygoid plates part of the cranial floor?
No
Generally describe the inferior aspect of the brain
Not flat
Step appearance
How many pairs of cranial nerves are there?
12
Where do the cranial nerves emerge from?
Inferior aspect of brain
Is the cranial floor flat?
No, it’s stepped
Why are there holes in the cranial floor?
To allow exit of cranial nerves
How are the fossae of the cranial floor arranged?
In stepwise configuration
What does the anterior cranial fossa support?
Frontal lobes
Where does the anterior cranial fossa sit?
Above and in front of middle cranial fossa
What does the middle cranial fossa support?
Temporal lobes
Where does the middle cranial fossa sit?
Behind and below anterior cranial fossa
What does the posterior cranial fossa support?
Brain stem
Cerebellum
Where does the posterior cranial fossa sit?
Behind and below middle cranial fossa
Which bones make up the anterior cranial fossa?
Horizontal plates of frontal bone
Lesser wing of sphenoid bone forms edge before step down
Very superior aspect of ethmoid bone
Where is the ethmoid bone?
Between eyes
Just above nose
What is the vertical plate of the ethmoid bone called?
Cristagalli
What are the holes on either side of the cristagalli in the ethmoid bone called?
Cribiform plate
Which bones make up the middle cranial fossa?
Greater wing of sphenoid anteriorly
Petrous part of temporal bone inferiorly = edge
Which bone makes up the posterior cranial fossa?
Occipital bone
What are the foramenae in the anterior cranial fossa?
Cribiform plate
What are the foramenae in the middle cranial fossa?
Hypophysial fossa Optic canal Superior orbital fissure Foramen rotundum Foramen ovale Foramen spinosum
What are the foramenae in the posterior cranial fossa?
Internal acoustic meatus
Jugular foramen
Hypoglossal canal
Foramen magnum
What structure goes through the cribiform plate?
Olfactory nerve
What structure goes through the hypophysial fossa?
Pituitary gland
What structures go through the optic canal?
Optic nerve
Ophthalmic nerve
What structures go through the superior orbital fissure?
Nerve to extraocular muscles
Branches of trigeminal nerve
What structure goes through the foramen rotundum?
Maxillary nerve
What structure goes through the foramen ovale?
Mandibular nerve
What structure goes through the foramen spinosum?
Middle meningeal artery
What structures go through the internal acoustic meatus?
Facial nerve
Vestibulocochlear nerve
What structures go through the jugular foramen?
Cranial nerve IX
Cranial nerve X
Cranial nerve XI
Internal jugular vein
What structure goes through the hypoglossal canal?
Hypoglossal nerve
How are the foramenae of the middle cranial fossa arranged?
Crescent on each side of body of sphenoid
Superior orbital fissure forms proximal half of crescent
In second part of crescent
- Round = foramen rotundum
- Oval = foramen ovale
- Little = foramen spinosum
How are the foramenae of the posterior middle cranial fossa arranged?
Vertical line
Internal auditory meatus in step down to posterior cranial fossa in petrous part of temporal bone
Jugular foramen in gap between petrous part of temporal bone and occipital bone
Hypoglossal canal related to foramen magnum
