Week 5

Question 1

What is the falx cerebri

Answer 1

○ The falx cerebri can be seen running through the midline of the cerebral hemispheres (longitudinal fissure)
○ It is a large fold of dura mater
○ It attaches anteriorly to a bony projection present at the midline called the crista galli of the ethmoid bone
It is attached to the tentorium posteriorly

Question 2

What is the tentorium cerebelli

Answer 2

○ Fold of dura mater that separates the cerebellum from the inferior portion of the occipital lobes
○ The fixed margins of the tentorium are attached to the posterior clinoid process
○ Its attached to the falx cerebri at this midline and this attachment contains the straight sinus

Question 3

What is the function of the dural folds

Answer 3

► Around the brain there is CSF which lies in the subarachnoid space and this CSF surrounds the brain and large folds and they protect the brain and they act as a mechanical cushion to prevent movement when there is trauma

Question 4

What are venous sinuses

Answer 4

It is like a vein except the walls of the vein is made up dura but it is lined with endothelium

Question 5

What do the deep venous drainage of the cerebrum empty into

Answer 5

into the great cerebral vein at the junction of the tentorium and the falx
○ The blood flows back the way inside the junction and this is caled the straight sinus which is a continuation of blood inside the great cerebral vein

Question 6

What is the superior sagittal sinus

Answer 6

○ Has a triangular appearance 
		○ Runs through the falx 
		○ Gets bigger as it reaches the back 
		○ Turns right once it reaches the posterior cranial fossa
		○ Receives veins from the cerebellum

Question 7

What is the transverse sinus

Answer 7

○ Superior sagittal sinus turns and the transverse sinus runs in the dura mater of the tentorium and makes its way forward

Question 8

What is the sigmoid sinus

Answer 8

○ Transverse sinus turns and leaves tentorium to run under dura in the floor of the cranial cavity in a deep groove in what is known as the sigmoid sinus

Question 9

What is the straight sinus

Answer 9

○ Inside junction of the falx and tentorium and the blood comes close to the superior sagittal sinus and runs into the attachment of tentorium
○ It runs back to the internal occipital protuberance and becomes the left transverse sinus

Question 10

How does the blood escape from the venous sinuses

Answer 10

► The blood escapes at the bottom through the jugular foramen at the base of the skull
► There is a connection between the two sides in what is called the confluence of sinuses

Question 11

What is the relevance of the ophthalmic veins

Answer 11

► The ophthalmic veins drain the orbit and bring the blood back to the cranial cavity to a sinus that runs to the side of the pituitary called the cavernous sinus

Question 12

Describe the cavernous sinus

Answer 12

○ Blood flows through little passageways, it is like a sponge in cross section
○ At the back end the cavernous sinus splits into 2 and the smaller one joins the upper end of the sigmoid sinus and the other one runs to the lower end
○ Blood flow through the sinus is slow
○ It is possible for bacteria from the face to enter the cavernous sinus and cause a blood clot in what is called a cavernous sinus thrombosis. The symptoms are a temperature and swollen eye.
○ There is a vessel called the sphenoidal emissary vein that brings blood in from the area of the upper jaw to the inside of the cranial cavity and bacteria from a dental abscess can come from this and enter the cavernous sinus to cause a thrombosis

Question 13

What is the diploe

Answer 13

○ Between outer and inner table of skull
○ Red bone marrow
○ Diseases of bone marrow may impact the skull

Question 14

What is the olfactory never

Answer 14

○ Olfactory bulbs and tracts can be seen
○ Olfactory nerves pass down to nasal cavity from these bulbs
○ The olfactory tract is the part that takes the information to the back of the forebrain
○ Enters the skull through the perforations in the cribriform plate of the ethmoid bone to join the olfactory bulb in the brain

Question 15

What is the optic nerves

Answer 15

○ They are tucked away
○ Optic chiasma can be seen
○ Pituitary gland sits close to where they are and so does the internal carotid artery
○ Nerve enters the skull through the optic canal of the sphenoid bone on its way from the retina
○ Both right and left optic nerves join at the optic chiasma, where many of the fibres cross to the contra lateral side before continuing into the brain as optic tracts

Question 16

What is the oculomotor nerve

Answer 16

○ Piercing the dura mater
○ Going to disappear under dura mater and going off into the orbit
Nerve lies within the lateral wall of the cavernous sinus and exits the skull through the superior orbital fissure of the sphenoid bone on its way to the orbit

Question 17

Whats the trochlear nerve

Answer 17

○ Runs in lateral wall of cavernous sinus and exits the skull through superior orbital fissure of the sphenoid bone on its way to the orbit
○ Supplies one eye muscle

Question 18

What is the trigeminal nerve

Answer 18

○ Disappears under the dura
○ Meckel’s cave is a space in the dura where the trigeminal ganglion can be found
○ If the dura was removed then the ophthalmic nerve can be followed to the superior orbital fissure and you can see the maxillary nerve and the mandibular nerve leaving through their bony openings
○ The trigeminal ganglion is the site of the sensory cell bodies

Question 19

What is the abducens nerve

Answer 19

○ Has a long course
○ Exits through the superior orbital fissure on its way to the orbit
It doesn’t lie in the wall of the cavernous sinus, it runs through the sinus close to the internal carotid artery

Question 20

What is the facial nerve

Answer 20

○ Runs close to vestibulocochlear nerve
○ Leaves the cranial cavity by passing through the internal acoustic meatus which leads to the facial canal within the temporal bone
○ The nerve exits the skull by the stylomastoid foramen of the temporal bone
○ It travels through the parotid gland

Question 21

What is the vestibulocochlear nerve

Answer 21

○ Nerve enters cranial cavity through the internal acoustic meatus of the temporal bone
○ It is the lateral one

Question 22

What is the glossopharyngeal nerve

Answer 22

○ Passes through the skull by the jugular foramen, between the occipital bone and temporal bone

Question 23

What is the vagus nerve

Answer 23

○ Passes through the skull by the jugular foramen, between the occipital bone and temporal bone

Question 24

What is the accessory nerve

Answer 24

○ Passes through the skull by the jugular foramen, between the occipital bone and temporal bone

Question 25

What is the hypoglossal nerve

Answer 25

○ Exits the skull through the hypoglossal canal in the occipital bone

Question 26

What is the crista galli

Answer 26

falx cerebri has its anterior attachment. Some times a pit can be seen in front of it called foramen caecum which is where the superior sagittal sinus starts. On each side of the crista galli there is a thin area of bone called the cribriform plate of the ethmoid bone which the olfactory nerve runs through

Question 27

Where does the pituitary gland sit

Answer 27

in the sella tursica/hypophyseal fossa - saddle shaped area.

Question 28

What is arcuate eminence

Answer 28

bony prominence on the middle fossa plate of the temporal bone and it indicates the situation of the superior semi-circular canal

Question 29

What is tegmen tympani

Answer 29

roof of the tympanic cavity. It is a thin plate of the petrous part of the temporal bone that separates the intracranial compartment and middle ear

Question 30

What is the clivus

Answer 30

Bony part of the cranium at the skull base, the pons sits on the clivus. In a young individual you may see the spheno-occipital synchondrosis here which allows the skull to grow in length

Question 31

What nerves pass through superior orbital fissure

Answer 31

allows passage of several nerves from the middle cranial fossa into the orbit - this includes the oculomotor nerve, the trochlear nerve, abducens nerve & ophthalmic branch of the trigeminal nerve

Question 32

What is foramen spinosum

Answer 32

where the middle meningeal artery (branch of the maxillary artery) comes into the cranial cavity. It runs in a groove between dura and the bone of the vault of the skull and goes out to the site and further towards the vault

Question 33

What is foramen lacerum

Answer 33

Looks lacy. Occupied by an unossified piece of hyaline cartilage.

Question 34

What passes through internal acoustic meatus

Answer 34

The labyrinthine artery accompanies the vestibulocochlear nerve through the internal acoustic meatus to supply blood to the internal ear. It is a branch of the basilar artery.

Question 35

What is the stylomastoid foramen

Answer 35

Facial nerve emerges from the temporal bone from here and comes out and turns forward into the parotid gland