Meninges, Blood Supply & Innervation of the Cranial Cavity

Question 1

How does the dura in the cranium differ from the dura in the spinal cord?

Answer 1

Has two layers:
1. Periosteal layer - intimately associated with bony surfaces of the cranium
2. Meningeal layer (continuous with spinal cord)
They relate closely wherever the dura is just lining the cranial cavity

Question 2

What are the four specialized partitions formed by the meningeal layer of the dura?

Answer 2

1. Falx cerebri
2. Falx cerebelli
3. Tentorium cerebelli
4. Diaphragma sellae

Question 3

What are dural sinuses?

Answer 3

Separations that are formed whenever the periosteal dura remains associated with the bone, and the meningeal dura is suspended off the bony surface.

Question 4

What are arachnoid granulations?

Answer 4

Areas where the arachnoid mater sticks out of the dura into the sinuses to allow recycling of CSF from subarachnoid space. New CSF is constantly being made and replaced. Found in superior sagittal sinus

Question 5

What are granular foveolae?

Answer 5

Cavities in the surface of the calvaria caused by invasion of arachnoid granulations across the dural space. Along lines of superior sagittal sinus

Question 6

Where does the arterial blood supply to the dura mater come from?

Answer 6

Majority comes from middle meningeal artery. All of its branches course between the two dural layers

Question 7

What is the falx cerebri, and what are its anterior and posterior attachments?

Answer 7

Dura partition separating the left and right cerebral hemispheres.
Anterior: Crista galli / Frontal crest of ethmoid bone
Posterior: Tentorium cerebelli

Question 8

What is the crista galli?

Answer 8

The frontal crest of ethmoid bone - sits on cribiform plate of ethmoid bone. Both sides have olfactory bulbs next to them (ethmoid bone forms roof of nose)

Question 9

What sinuses are related to the falx cerebri?

Answer 9

Superiorly: Superior sagittal sinus
Inferiorly along free border: Inferior sagittal sinus
Inferiorly / posteriorly: Straight sinus

Question 10

What is the tentorium cerebelli? What are its anterior attachments?

Answer 10

Dura partition separating cerebrum from cerebellum (tent of cerebellum)
Anterior: Right and left petrous ridge of temporal bone
Proceeds posteriorly along occipital bone in a horizontal plane until meeting its partner at midline

Question 11

What is the tentorial notch?

Answer 11

The opening along the free edge of the tentorium cerebelli that accommodates the passage of the brainstem into the posterior cranial compartment

Question 12

What is the diaphragma sellae? What is the purpose of its opening?

Answer 12

Dura partition covering the hypophyseal fossa (sella turcica). Contains a midline opening to allow the infundibular stalk of the pituitary to pass from hypothalamus to pituitary gland

Question 13

What provides sensory innervation to the dura of anterior cranial fossa?

Answer 13

Ophthalmic branch of cranial nerve (V1)

Includes: falx cerebri, tentorium cereblli, diagraphma sellae, and dura lining of anterior cranial fossa

Question 14

What provides sensory innervation to the dura of middle cranial fossa?

Answer 14

Medially: Maxillary division of cranial nerve 5 (V2)
Laterally: Mandibular division of cranial nerve (V3)

Question 15

What provides sensory innervation to the dura of the posterior cranial fossa?

Answer 15

C2 and C3

yes, cervical nerves, because fuck it

Question 16

Can the pia mater be separated from the brain tissue?

Answer 16

No, just like spinal cord

Question 17

What is the direction of venous flow in the brain and why?

Answer 17

Bidirectional - because the dural sinus system which contains cerebral veins has no valves. This can lead to easy spread of infection or cancer throughout the brain

Question 18

What are diploic veins? What is important about them?

Answer 18

Veins residing within the spony bone of cranial plates that empty directly into dural sinuses.

important: They connect directly to veins of the scalp, and can serve to spread infection from the outside

Question 19

What are emissary veins? What is an example?

Answer 19

Veins that run directly from the scalp to the dural sinuses.

Example: Parietal emissary veins, passing through the parietal foramen

Question 20

What passes thru the parietal foramen?

Answer 20

Parietal emissary veins

Question 21

What is the great cerebral vein / where does it empty into?

Answer 21

Largest of all cerebral veins, it is a midsagittal vein that empties into the proximal straight sinus

Question 22

What are dural sinuses lined by and formed by?

Answer 22

Majority are formed by both periosteal and meningeal layers of dura mater. All sinuses are lined by same endothelium that lines the vasculature

Question 23

What sinuses are not formed by both periosteal and meningeal layers of dura, and why?

Answer 23

Inferior sagittal sinus and straight sinus, because they are not associated with bony cranial cavity. They are only formed by the meningeal dura

Question 24

What is the superior sagittal sinus?

Answer 24

Located in superior border of falx cerebri. Drains directly into the confluence of sinuses in the occipital region. Important for draining CSF, also has diplopic and emissary veins

Question 25

What is the inferior sagittal sinus?

Answer 25

Located in free margin of falx cerebri and receives cerebral veins to drain into the straight sinus

Question 26

What is the straight sinus?

Answer 26

Located in midsaggital plane between the base of falx cerebri and tentorium cerebelli. Receives venous return from inferior sagittal sinus and great cerebral vein to drain into the confluence of sinuses

Question 27

What is the occipital sinus?

Answer 27

Located in base attachment of falx cerebelli (below tentorium cerebelli), receives veins from vertebral venous plexus (distal regions of cerebellum + brain stem). Drains directly into confluence of sinuses

Question 28

Where is the confluence of the sinuses?

Answer 28

Midline within tentorium cerebelli, and its occipital attachment just below the internal occipital crest.

Question 29

What sinuses attach directly into the confluence of sinuses?

Answer 29

Superior sagittal sinus, straight sinus, left and right transverse sinuses, occipital sinus

Question 30

What is the location of the transverse sinuses?

Answer 30

Contained within the attachment of the tentorium cerebelli, attaches to occipital/parietal/temporal bony plates. There are right and left ones

Question 31

What is the primary function of the transverse sinuses?

Answer 31

Venous route for the confluences of sinuses to drain into the right or left sigmoid sinuses

Question 32

What are the sigmoid sinuses?

Answer 32

Paired sinuses in S-shaped groove of temporal bone, leading to jugular foramen. They receive blood from superior petrosal sinuses and transverse sinuses to supply blood to jugular bulb (and ultimately the IJV)

Question 33

Where are the cavernous sinuses located?

Answer 33

Located along the lateral wall of the body of the sphenoid bone, next to sella turcica
->paired

Question 34

What nerves and artery runs through the cavernous sinus?

Answer 34

Nerves:

1. V1
2. V2
3. CN3 - Oculomotor
4. CN4 - Trochlear
5. CN6 - Abducens

Artery:
Internal carotid artery (cavernous part)

Question 35

What gives venous contribution to the cavernous sinus?

Answer 35

Ophthalmic veins, emissary veins, pterygoid plexus, sphenoparietal sinuses, and basilar sinus

Question 36

Where does the cavernous sinus empty into?

Answer 36

Proximal end of sigmoid sinus, superior petrosal sinus

Question 37

What are the sphenoparietal sinuses?

Answer 37

Located along posterior edges of the lesser wing of the sphenoid bone, receive venous input from diploic veins, empty into cavernous sinus

Question 38

What are the intercavernous sinuses?

Answer 38

Located along surface of diaphgrame sellae, proves communication between left and right cavernous sinuses

Question 39

What are the superior petrosal sinuses?

Answer 39

Located within the tentorium cerebelli at tits attachment to the petrous ridge of the temporal bone. Receives venous return from cavernous sinuses and empties into proximal sigmoid sinus

Question 40

What are the inferior petrosal sinuses?

Answer 40

Located in the groove between the parietal and occipital bones, communicate directly with cavernous and basilar sinuses, and empty into jugular bulb

Question 41

What is the basilar sinus?

Answer 41

Also called basal venous plexus, it is located on the clivus of the occipital bone and communicates with inferior petrosal sinus, cavernous sinus, and intercavernous sinuses

Question 42

How do the internal carotid and vertebral arteries communicate with eachother?

Answer 42

A ring of arteries that make up the circle of Willis

Question 43

Where does CN2 run in relation to the cavernous sinus?

Answer 43

Runs over top of it, above the diaphragma sellae (it is headed to towards the optic foramen, above the superior orbital fissue

Question 44

What is the course of the vertebral arteries?

Answer 44

First branch off of subclavian artery, dive into anterior muscles of neck, ascend through transverse cervical foramen of C6-1. Makes a sharp medial turn on posterior arch of CV1, pierces the posterior atlantooccipital membrane, pierces dural sac to enter subarachnoid space.

Question 45

What is the terminal structure of the vertebral arteries?

Answer 45

After piercing into the subarachnoid space, they enter through the foramen magnum and meet to form the basilar artery on the ventral surface of the brain stem (near the basilar sinus)

Question 46

What is the course of the internal carotid artery before entering the carotid canal (cervical part)?

Answer 46

Branch from common carotid around CV4, runs POSTERIOR to the external carotid. Enters through carotid canal via the external opening at the base of the skull, and runs anteriorly / medially

Question 47

What are the sections of the internal carotid and what do they correspond to?

Answer 47

1. Petrous part - 1st part after cervical part, within brain. Runs along petrous temporal bone
2. Cavernous part - makes 90 degree vertical turn. to be facing up, enters middle cranial fossa here and is within the cavernous sinus. Runs along this horizontally

Will make 150 degree turn

Question 48

What is the clinoid part of the internal carotid?

Answer 48

Where it makes the carotid syphon, a 150 degree ascending posterior turn from its anterior path through the carotid sinus

Question 49

What is the lacerum part of the internal carotid?

Answer 49

The internal carotid as it passes through the cavernous sinus (over foramen lacerum), before making the carotid syphon

Question 50

What is the cerebral part of the internal carotid? What are its subdivisions?

Answer 50

After the clinoid part, it passes lateral to the optic nerve to give off its terminal branches.
Subdivisions:
Ophthalmic
Communicating (distal segment)

Question 51

Why is the middle meningeal artery particularly susceptible to injury?

Answer 51

Passes through the pterion, the thinnest region of bones in the cranium. A sharp impact can rupture the periosteal layer of dura and middle meningeal artery.

Question 52

What is an epidural hematoma and what is a common cause?

Answer 52

Pooling of blood between bony skull and periosteal layer of dura, where the dura mater is dissected away from the bone. Common cause: pterion fracture leading to middle meningeal hemorrhage.

Can lead to death by compressing / displacing dural sac against brain if untreated

Question 53

What is carotid artery stenosis?

Answer 53

The most common cause of strokes is embolic blockage within the carotid bulb and or in the initial segment of the internal carotid artery.

85% of strokes are related to ischemia.

Can be treated by surgical removal of plaque and surrounding epithelium