4 - Skull Anatomy Flashcards
Name for upper part of cranium
Cranial vault
Name for lower part of the cranium
Cranial floor
Structure of skull bones
Hard outer layer of bone surrounding a soft, spongy layer
Suture where frontal and parietal bones joint
Coronal suture
Name of suture between parietal bones
Sagittal suture
Name of suture where parietal and occipital bones joint
Lambdoid suture
Name for lateral suture where frontal, parietal, temporal and sphenoid bones join
Pterion
Sphenoid bone
Part of skull near orbit
Particularly dangerous area to fracture skull
Pterion. Skull is thin, overlies an artery
Two parts of frontal bone
Vertical part (forms forehead) Horizontal part (projection into the head, where there is a 90 degree bend into the orbit - also called orbital plates). Forms part of cranial floor
Shape of parietal bones
Roughly rectangular, moulded to contour of brain
Shape of occipital bone
Relatively flat, moulded to contour of brain. Very prominent bulge (external occipital protuberance).
Temporal bone
Most anterior part is called the ‘squamous part’ Has three bony projections from squamous part.
Three bony processes coming off temporal bone
1) Anterior projection is the zygomatic process of the temporal bone. Articulates with the zygoma (cheekbone). 2) Mastoid process projects posteriorly, inferiorly, has air cells, place where muscles attach. 3) Deep process is styloid process. Sharp point. Muscles associated with midline structures (eg tongue) attach here.
Structure on the interior part of temporal bones
Petrous part of the temporal bone. A wedge-shaped part of bone that projects into cranial cavity, forming part of cranial floor.
Sphenoid bone
Not really visible from exterior of skull. Mostly within the skull. Made up of greater, lesser wings, superior orbital fissure.
*Sphenoid bone
Where does the pituitary gland sit?
In the body of the sphenoid
Telencephalon
Cerebral hemispheres
Metencephalon
Pons and cerebellum
Number of cranial nerves
Twelve pairs
Fossae of the cranial base
Anterior, middle and posterior cranial fossae
What does the anterior cranial fossa house?
Frontal lobe
What makes up anterior cranial fossa?
Frontal bones, lesser wing of sphenoid, ethmoid bone
Through which structure do axons of olfactory epithelium travel?
Cribiform plate of ethmoid bone
What forms the middle cranial fossa?
Greater wings of sphenoid anteriorally, petrous part of temporal bone posteriorally
What makes up posterior cranial fossa?
Occipital bone
Foramen in anterior fossa
Cribiform plate (olfactory nerve)
Foraminae in middle cranial fossa 1 2 3 4 5 6
• Hypophysial fossa (pituitary gland) • Optic canal (optic nerve, ophthalmic artery) • Superior orbital fissure (nerves to extraocular muscles and branches of trigeminal nerve) • Foramen rotundum (maxillary nerve) • Foramen ovale (mandibular nerve) • Foramen spinosum (middle meningeal artery)
Foraminae in posterior cranial fossa 1 2 3 4
• Internal acoustic meatus (facial and vestibulocochlear nerves) • Jugular foramen (IX, X, XI, internal jugular vein) • Hypoglossal canal (hypoglossal nerve) • Foramen magnum
Path of middle meningeal artery in skull
Enters skull through foramen spinosum, then grooves in bone outwards
Location of internal auditory meatus
In the more vertical, posterior part of petrous temporal bone
Location of jugular foramen
In the split between the petrous temporal bone and the occipital bone. Not a hole in a bone, but a space between two bones
Location of hypoglossal canal
In occipital bone, between occipital condyles
What does the dura attach to?
Skull and arachnoid
Most delicate of meninges
Pia mater
What are associated with the meninges?
Potential spaces (extradural space between dura and skull, subdural space between dura and arachnoid, subarachnoid space)
What happens if the meningeal artery is ruptured?
Extradural space
What often leads to a subdural haemorrhage?
Venous bleeding.
Where does CSF circulate?
Subarachnoid space
Projections of dura that don’t line interior surface of the skull 1 2 3 4
1) Falx cerebri (sickle-shaped, in sagittal plane) 2) Falx cerebelli 3) Tentorium cerebelli 4) Diaphragma sellae
Role of dural projections
Prevent twisting of brain
Attachments of falx cerebri
In line with sagittal suture, back to the interior of the external occipital protuberance
Tentorium cerebelli 1 2 3 4
1) In the horizontal plane. 2) Crescent-shaped. 3) Grooves in posterior cranial fossa. 4) Separates cerebral hemispheres above from cerebellum below
Falx cerebelli
Separates cerebellar hemispheres
Diaphragma cellae
Roofs the pit in the body of the sphenoid
Name for sinus formed by dura splitting to form falx cerebri
Superior sagittal sinus
Where does venous blood of the brain drain?
Into dural sinuses. Where dura splits to form dural partitions. These form dura, epithelium-lined sinuses.
What drains into dural sinuses? 1 2 3
1) Emissary veins from scalp. 2) Diploic veins (from spongy bit of skull) 3) Blood from brain
