Cranial Contents

Question 1

How is a dural venous sinus formed?

Answer 1

By the splitting of the meningeal layer of dura from the endosteal layer of dura. The triangular space formed is a dural venous sinus.

Question 2

What is the function of a dural venous sinus?

Answer 2

It collects blood from the scalp (emmissary vv.); from the thin bone of the calvarium (diploic vv.) as well as from the superficial cerebral vv. and deep cerebral vv. that drain the brain and brain stem.

Question 3

What is the function of an arachnoid villous?

Answer 3

It allows cerebrospinal fluid (CSF) from the subarachnoid space to escape into the dural venous sinus - thus regulating the amount of CSF present since it is continually produced.

Question 4

How is an arachnoid villous formed?

Answer 4

A small finger-like projection of arachnoid protrudes through a small hole in the meningeal layer of dura - gaining access to the dural venous sinus.

Question 5

What is an arachnoid granulation ?

Answer 5

An old arachnoid villus that has grown across lumen of the venous sinus and begins to invaginate it’s way into the bone of the calvarium.

Question 6

Into what bony structure do these granulations embed themselves?

Answer 6

The inner bony diploe (plate) of the calvarium (temporal and/or occipital bone primarily).

Question 7

Be able to trace the pathway of the flow of venous blood within the dural venous sinuses?

Answer 7

From the anterior region of the superior sagittal sinus it drains posteriorly to the confluence of sinuses. Blood from the occipital sinus comes up from below to the confluence. Blood from the inferior sagittal sinus and deep cerebral vein pass back to the confluence via the straight sinus. From the confluence, all blood passes anteriorly in a horizontal fashion along the right and left transverse sinuses down the sigmoid sinus to the jugular foramen

Question 8

Where does the venous blood leave the cranial cavity?

Answer 8

Via the jugular foramen.

Question 9

What vessel forms at the point of exit?

Answer 9

The internal jugular vein.

Question 10

What two sinuses drain from the cavernous sinus? to where specifically?

Answer 10

The superior petrosal sinus drains posteriorly to the upper region of the sigmoid sinus; the inferior petrosal sinus drainly inferiorly to the lower region of the sigmoid sinus.

Question 11

What two venous pathways flow to the cavernous sinus?

Answer 11

The sphenoparietal sinus and the ophthalmic vein.

Question 12

Why is the venous pathway from the face clinically important?

Answer 12

Infection from the face (pimples, boils, etc.) can flow posteriorly through the valveless veins back into the cavernous sinus.

Question 13

How is a dural fold formed?

Answer 13

By the fusion of two layers of meningeal dura.

Question 14

Be able to list the 4 dural folds within the cranial cavity and what components of the CNS they effectively separate.

Answer 14

Falx cerebrum: rt/lt cerebral hemispheres;
Falx cerebelli: rt/lt cerebellar hemipsheres;
Tentorium cerebelli: overlying cerebral hemispheres from underlying cerebellar hemispheres;
Diaphragma sellae: nothing.

Question 15

What sinus is formed in the attached margin of each dural fold?

Answer 15

Falx cerebrum: superior sagittal sinus;
falx cerebelli: occipital sinus;
tentorium cerebelli: rt/lt transverse sinuses;
diaphragma sellae: none.

Question 16

What is formed by the free edge of the tentorium cerebelli?

Answer 16

The tentorial notch.

Question 17

What is found within this opening?

Answer 17

The brain stem

Question 18

Which cranial nerve is found just under the free edge of the tentorium cerebelli?

Answer 18

CN IV (trochlear).

Question 19

What sinus is found within the junction of the falx cerebri with the tentorium?

Answer 19

The straight sinus

Question 20

What is the function of the straight sinus?

Answer 20

It drains venous blood from the inferior sagittal sinus (in the free edge of the falx cerebri) as well as from the deep brain regions via the deep cerebral vein (of Galen).

Question 21

Where does the falx cerebri attach anteriorly?

Answer 21

The crista galli (of the ethmoid bone).

Question 22

To what 4 structures does the diaphragma sellae attach?

Answer 22

The two anterior clinoid processes and the two posterior clinoid processes.

Question 23

Which four major vessels arise in the neck and eventually supply blood to the brain?

Answer 23

The left and right common carotid arteries as well as the left and right vertebral arteries.

Question 24

Be able to label a diagram of the arterial circle at the base of the brain.

Answer 24

This diagram is important (page 347) for the lab exam as well as the written.

Question 25

What are the terminal branches of the basilar a.?

Answer 25

The right and left posterior cerebral aa.

Question 26

What are the various anatomical relationships superior to the diaphragma sellae?

Answer 26

The optic chiasm and the ophthalmic artery.

Question 27

Why are these relationships clinically important?

Answer 27

Compression of either by an enlarging hypophysis from below will result in blindness.

Question 28

Through what opening does the internal carotid artery enter the bone of the skull?

Answer 28

The opening of the cartoid canal.

Question 29

In which direction does the artery pass once in this bony canal?

Answer 29

Medially in a horizontal fashion.

Question 30

Through what opening does the internal carotid exit this canal?

Answer 30

The foramen lacerum.

Question 31

Into what structure does the internal carotid immediately enter?

Answer 31

The cavernous sinus.

Question 32

What is the anatomical shape of the internal carotid within this structure?

Answer 32

“S”-shaped - a siphon.

Question 33

How does the internal carotid gain access to the cranial cavity?

Answer 33

It passes through the dural roof of the cavernous sinus.

Question 34

What is the first branch of the internal carotid?

Answer 34

The ophthalmic artery.

Question 35

What are the terminal branches of the internal carotid?

Answer 35

The middle and anterior cerebral aa.

Question 36

Be able to list all 12 cranial nerves and their various modalities (motor, sensory,
parasympathetic - or any combination of these).

Answer 36

Sensory only: CN I, II, VIII (+ CN V1 and V2); motor only: CN IV, VI, XI, and XIII; motor and sensory: CN V - specifically V3; motor and parasympathetic: CN III; motor, sensory and parasympathetic: CN VII, IX, and X.

Question 37

Which is the only cranial nerve to exit the dorsal aspect of the brainstem?

Answer 37

The trochlear (CN IV).

Question 38

What are the four autonomic ganglia of the head?

Answer 38

Ciliary, pterygopalatine (sphenopalatine), submandibular & otic.

Question 39

Which division of the ANS synapse in these ganglia?

Answer 39

The preganglionic parasympathetic fibers.

Question 40

Which cranial nerve(s) supply preganglionic fibers to each one?

Answer 40

Ciliary: CN III;

pterygopalatine: VII;
submandibular: VII;
otic: IX.

Question 41

Which branch of CN V takes postganglionic fibers to specific target organs?

Answer 41

Ciliary: V1; pterygopalatine: V2; submandibular: V3; otic: V3.

Question 42

Be able to match each cranial nerve with the foramen through which it leaves the cranial cavity and the foramen by which it exits onto the face or skull (if required).

Answer 42

CN I - accesses cranial cavity via the cribriform plate of the ethmoid; CN II - optic canal;
CN III, IV, VI and V1 - superior orbital fissure;
V2 - foramen rotundum;
V3 - foramen ovale;
VII and VIII - internal acoustic meatus;
IX, X & XI - jugular foramen;
XII - hypopglossal canal.

Question 43

Which cranial nerves are associated with the cavernous sinus and why is this clinically important?

Answer 43

CN V1, IV, VI, III and perhaps V2. They become involved in cavernous sinus syndrome.

Question 44

What is cavernous sinus syndrome and which cranial nn. are associated with it?

Answer 44

Infectious thrombi pass to the cavernous sinus and lodge there and cause eventual paralysis of the eye - affecting the nerves of the extraocular mm. The abducens (CN VI) is affected first as it passes through the cavernous sinus - the others (III, IV, V1 and perhaps V2) are embedded in the lateral dural wall so are affected later.

Question 45

What are the symptoms of Horner’s syndrome.

Answer 45

Pupillary constriction; ptosis (drooping of upper eyelid); vasodilation and dry face.

Question 46

What is the anatomical basis for Horner’s syndrome?

Answer 46

The postganglionic sympathetic fibers arising from the superior cervical ganglion that hitch-hike along the carotid aa. to their target organs are disrupted. Pupillary constriction results from paralysis of the dilator pupillae m.; ptosis is the result of by paralysis of the superior tarsal m.; vasodilation and dry face are due to the lack of sympathetic innervation to the blood vessels and glands of the skin of the face.

Question 47

What specific structures compose the pharyngeal plexus?

Answer 47

The cranial accessory fibers of CN XI) distributed by the vagus n (XI via X); the fibers of the glossopharyngeal n. (CN IX); and postganglionic sympathetic fibers.

Question 48

What is/are the modalities of each component of the pharyngeal plexus?

Answer 48

Motor, sensory and sympathetic.

Question 49

What are the primary functions of the pharyngeal plexus?

Answer 49

Motor to the pharyngeal constrictors and sensory to the mucosa of the pharynx.