Session 1: The Cranium, Cranial Nerves and Meninges; Dural Venous Sinuses, Blood Supply of Head and Neck Flashcards
How many bones is the skull composed of? (excluding the 3 ossicles)
22 bones
How are the bones of the skull attached together?
By immovable sutures (fibrous joints)
Which is the only movable bone of the skull?
Mandible
What does the cranial vault ossify in?
Membrane
What does the skull base ossify in?
Cartilage
At what level does the spinal cord terminate? What is the structure it terminates into called?
L1; the conus medullaris
At what level does the dural sac terminate?
S2
What does the spinal cord become at the level of L1?
The cauda equina
Name the parts of the ethmoid bone.
Cribiform plate with crista galli
Perpendicular plate
Superior and middle conchae
Ethmoidal air cells
Name the parts of the frontal bone.
Frontal air sinuses
Superior ciliary ridges
Supraorbital notches
Describe the development of the frontal bone. What is the name given if a suture is still present in adulthood?
In two parts at birth but usually fuses early in life. Metopic suture.
Name the parts of the sphenoid bone.
Greater and lesser wings Medial and lateral pterygoid plates Sella turcica for the pituitary gland Optic canals Superior orbital fissures Foramen ovale Foramen rotundum Foramen spinosum
Name the parts of the occipital bone.
Squamous and basal parts Hypoglossal canals Foramen magnum Occipital condyles Occipital protuberance Superior nuchal line Emissary holes
What are the 4 main parts of the temporal bone?
Petrous part
Squamous part
Tympanic part
Styloid part
What are the main features of the squamous temporal bone?
Zygomatic process
Mandibular fossa
What are the main features of the petrous part of the temporal bone?
Middle and inner ear
IAM
Facial canal
Air cells in mastoid process
What are the main features of the tympanic part of the temporal bone?
EAM
Attachment of tympanic membrane
What are the main features of the styloid process?
Attachment of ligaments and muscles
Adjacent to stylomastoid foramen (where CN VII emerges)
Name the parts of the parietal bone.
Contains foramina for emissary veins that connect scalp veins with venous dural sinuses inside the skull.
What are the three tiers of the floor of the cranial cavity called?
Cranial fossae.
Describe the anterior cranial fossa.
Cribiform plate of ethmoid
Midline projection - crista galli
Falx cerebri attaches to crista galli
Occupied by frontal lobes of brain
Describe the middle cranial fossa.
Central portion formed by body of sphenoid, pituitary fossa.
Sella turcica = pituitary fossa + clinoid processes
Houses temporal lobes of brain laterally.
Contains: foramen spinosum (middle meningeal vessels), foramen ovale, foramen lacerum (cartilage filled), foramen rotundum, superior orbital fissure
Describe the posterior cranial fossa.
Houses the cerebellum and much of the brainstem. In its floor is the foramen magnum, and anterior to its occipital condyles lie the hypoglossal canals.
Between each petrous temporal and occipital bone is the jugular foramen.
Posterior wall of each petrous temporal bone is the IAM.
What are the 3 layers of the meninges?
Dura mater, arachnoid mater, pia mater
How many layers of dura mater are there? What are they called?
2, outer endosteal layer and inner meningeal layer.
What is the outer endosteal layer of dura mater continuous with?
Pericranium through sutures and foramina
When do the layers of dura mater diverge?
To enclose the venous sinuses
How many layers of dura mater enclose the spinal cord?
1
What do reflections of the meningeal layer of dura mater form? How many of these reflections are there?
Four septa or dural folds
What are the names of the 4 dural folds? What are they formed by?
Falx cerebri, tentorium cerebelli, falx cerebella, diaphragma sellae.
What does the falx cerebri separate?
The two cerebral hemispheres
What does the tentorium cerebelli separate?
Occipital lobe and cerebellum
What does the falx cerebelli separate?
Cerebellar hemispheres
What does the diaphragma sella cover?
Pituitary fossa in the sella turcica of the sphenoid bone.
Which of the pia and arachnoid mater is vascular?
Pia mater highly vascular, arachnid mater non-vascular.
Is the spinal or cranial pia mater thinner?
Cranial
Which structure of the spinal cord does the pia mater follow into?
Ventral median fissure
Is the spinal or cranial arachnoid thinner?
Spinal
What is the name given to larger accumulations of CSF in the brain?
Subarachnoid cisterns
Where does the spinal epidural space lie?
Between the dura and vertebral periosteum
What does the spinal epidural space contain?
Loose tissue, venous plexuses and lymphatics
Where does the subarachnoid space extend to in an adult?
Termination of the lumbar cistern, at the level of S2.
Where does the superior sagittal sinus run between?
Begins at crista galli, runs in the superior margin of falx cerebri.
What does the superior sagittal sinus run into?
Right transverse sinus.
Where does the inferior sagittal sinus run?
Inferior margin of falx cerebri.
What does the inferior sagittal sinus form? What is it joined by to form this?
Straight sinus. Joined by great cerebral vein and left and right basal veins.
What does the straight sinus form?
Left transverse sinus.
Which two sinuses form the sigmoid sinus?
Transverse sinus + superior petrosal sinus
Which bone does the sigmoid sinus groove?
Petrous temporal bone
Which foramen does the sigmoid sinus pass through?
Jugular foramen.
Which two sinuses join to form the IJV?
Sigmoid sinus and inferior petrosal sinus
What lies laterally to the jugular foramen?
Mastoid air cells
Which two structures does the greater petrosal sinus join?
Cavernous sinus and the transverse sinus.
Which sinus drains the cavernous sinus into the IJV?
Inferior petrosal sinus.
Where does the cavernous sinus lie?
Either side of the body of the sphenoid.
Which veins does the cavernous sinus receive?
Superior and inferior opthalmic veins.
How does the cavernous sinus create extracranial to intracranial connections?
Via the facial vein and pterygoid plexus.
What runs through the cavernous sinus?
ICA + VI.
What lies in the lateral wall of the cavernous sinus?
III, IV, Va, Vb.
What does the filum terminale connect?
End of spinal cord (L1) which end of dural sac (S2)
What is the filum terminale made of?
Pia mater
What comes from the ventral aspect of the spinal cord and what comes from the dorsal aspect?
Anterior - motor
Posterior - sensory
What do the meningeal layers surrounding each nerve fuse with as the nerve leaves its intervertebral foramen?
Epineurium of the nerve root
What does the meningeal artery arise from?
Vertebral artery
What do the posterior cerebella arteries supply?
Occipital lobes of the cerebrum.
Which 4 bones meet at the pterion.
Frontal, Parietal, Greater wing of sphenoid, Temporal