Meninges

Question 1

What meningeal coverings are a part of the leptomeninges?

Answer 1

Arachnoid and pia mater

Question 2

Generally, what is dura mater?

What’s its main fcn?

Answer 2

A thick connective tissue membrane that serves as the periosteum of the inside of the skull
- Main fcn is to suspend the brain (protect from trauma)

Question 3

Explain the main layers of the dura mater.
Which contains the meningeal aa.?
What’s in b/w?

Answer 3

1. Outer periosteal layer: firmly attached to skull; contains the meningeal aa.
2. Inner meningeal layer: in close contact w/arachnoid and continuous w/spinal dura
3. Dural venous sinuses

Question 4

What is the space called b/w the dura and the cranium?

Answer 4

Trick- there is none (except in pathological conditions, then call it cranial epidural space)

Question 5

What important things are contained in the spinal extradural space?

Answer 5

• Venous plexuses

- CT

Question 6

What innervates the dura?

Answer 6

Anterior: CN V
Posterior: cervical nn. of cervical plexus
(this is a source of headaches)

Question 7

Name and approximate the 4 main dural folds.

Answer 7

1. Falx cerebri–vertically divides cerebrum
2. Falx cerebelli–vertically divides cerebellum
3. Tentorium cerebelli–horizontal tent over the cerebellum
4. Diaphragma sellae–allows passage of pituitary stalk (pit sits beneath it)

Question 8

What is the tentorial notch?

Answer 8

Exit pathway for the brainstem through the anterior tentorium cerebelli

Question 9

What sinus is on the superior border of the falx cerebri?
Inferior border?
What connects them at their posterior ends?

Answer 9

• Superior sagittal sinus
• Inferior sagittal sinus
• Straight sinus

Question 10

What sinus is at the falx cerebelli, against the occiput?

Answer 10

• Occipital sinus

Question 11

1. What are the dilated spaces at the external occipital protuberance?
2. What are their horizontal extensions?
3. What is the continuation of #2, into the IJV?

Answer 11

ConTraSig

• Confluence of sinuses
• R and L transverse sinuses
• R and L sigmoid sinuses

Question 12

Where are the paired cavernous sinuses located?

What connects them?

Answer 12

• Lateral aspect of the body of the sphenoid

- Intercavernous sinus

Question 13

What sinus runs along the inferior surface of the lesser wings of the sphenoid?

Answer 13

• Paired sphenoparietal sinuses

Question 14

What sinuses run thru the petrous part of the temporal bone?
Which one ends at the IJV?

Answer 14

• Paired superior petrosal sinuses and paired inferior petrosal sinuses
• Inferiors ones end at IJV

(they come from cavernous sinus)

Question 15

What sinus sits just posterior to the sella turcica of the sphenoid?

Answer 15

Basilar sinus

Question 16

What do emissary vv. do?

What’s a pathology associated w/them?

Answer 16

• They connect the extracranial veins to the dural venous sinuses inside the cranium.
• Pathway for infection to spread from face/scalp to brain

Question 17

Fcn of arachnoid trabeculae?

Answer 17

Suspends the brain

Question 18

Where is CSF drained into?
Through what structures?
From where?

Answer 18

• Dural venous sinuses (to venous system)
• Arachnoid villi (clusters of villi = granulations)
• From: subarachnoid space

Question 19

Besides arachnoid villi, what prevents CSF from leaking from the subarachnoid space into the veinous system or from the dura back into the CSF?

Answer 19

Arachnoid barrier containing tight junctions

Question 20

Why does CSF flow naturally from the SAS into the dural venous sinuses?
If this was altered, what would happen?

Answer 20

• Pressure in SAS higher than that of venous sinuses

- If this was reversed, venous blood could not get back into SAS because of valves in arachnoid villi

Question 21

What is on the side of pia mater opposite the arachnoid mater?

Answer 21

Astrocyte end feet that carpet the surface of the CNS

Question 22

What layers are on either side of the spinal epidural space?

Answer 22

• Periosteum

- Dura

Question 23

Spinal dura and arachnoid mater end at what vertebral level?

Answer 23

S2

Question 24

The spinal cord ends at what vertebral level?

Where would be a safe place to perform an LP?

Answer 24

• L1/L2

- L3/L4

Question 25

What meningeal layer provides the filum terminale?

Answer 25

Pia mater

Question 26

What meningeal layer are denticulate ligaments made of?

Answer 26

Pia mater

Question 27

What type of bleed would probably be caused by tearing a cerebral vein?

Answer 27

Subdural bleed

Question 28

What type of bleed would probably be caused by tearing a cerebral artery?

Answer 28

Subarachnoid bleed

Question 29

What type of bleed would probably be caused by tearing a meningeal artery?

Answer 29

Epidural bleed

Question 30

What brain vesicle contains the lateral ventricles? Third ventricle? Fourth ventricle?

Answer 30

- Telencephalon - Diencephalon - Rhombencephalon

Question 31

Explain the pathway of CSF flow in the ventricles to the SAS

Answer 31

``` 2 lateral ventricles -> 2 interventricular foramina of Monro -> 3rd ventricle -> Cerebral aqueduct of Sylvius -> 4th ventricle -> Median aperture (foramen of Magendie) and 2 lateral apertures (foramina of Luschka) -> SAS ```

Question 32

Name the different parts of a lateral ventricle.

Answer 32

- Frontal (ant) horn - Temporal (inf) horn - Occipital (post) horn - Body (sup) - Atrium (b/w them)

Question 33

What secretes CSF? | Where is this usually found?

Answer 33

- Choroid plexus | - Roof of 3rd + 4th ventricles, + medial wall of lateral ventricles

Question 34

What is the nl rate of CSF produced/day? How much do we have ahorita? How much of this is in the ventricles?

Answer 34

- 500mL/day - 90-150 mL - 23 mL in ventricles (rest in SAS)

Question 35

What types of cells surround the choroid plexus? | What is a second, special name for these cells?

Answer 35

Specialized ependymal cells, interconnected by tight junctions. - These cells are specialized as a secretory epithelium called the choroid epithelium.

Question 36

What is the intervening neural tissue b/w the inner lining of the ventricle and the pia mater?

Answer 36

There is none

Question 37

Besides pia mater and specialized ependymal cells, what else is invaginated inside the choroid plexi (the 3rd layer)?

Answer 37

Vascular CT (bv's)

Question 38

What area of SAS is situated b/w the medulla and the inferior surface of the cerebellum?

Answer 38

Cisterna magna

Question 39

What are a few main functions of the CSF?

Answer 39

- Mechanical support/cushioning - Removal of metabolites - Route to spread neuroactive hormones

Question 40

What are 3 key facts about the composition of the CSF, regarding proteins, glucose, and salts, as compared to normal serum?

Answer 40

- Trace protein in CSF - Less [glc], [Ca2+], [K+] vs. serum - More [Na+], [Cl-], [Mg2+] vs. serum

Question 41

What is hydrocephalus? | Explain the 2 main types of hydrocephalus.

Answer 41

Dilation of the ventricles - Communicating: obstruction occurs after CSF leaves the ventricles, hence the ventricles can still communicate - Non-communicating: obstruction occurs b/w the ventricles, most often the cerebral aqueduct ("aqueductal stenosis")

Question 42

What are the 2 circumventricular organs that we need to know? What are defining characteristics and some key facts about circumventricular organs?

Answer 42

- Area postrema (sensory) and neurohypophysis (secretory) - Lack BBB; extensive vasculature; - Play key role in Na/H2O balance, CV regulation, energy metabolism, and immunomodulation

Question 43

What is the area prostrema thought to be responsible for?

Answer 43

Vomiting (chemo can affect this area)

Question 44

To which part of the lateral ventricles is the interventricular foramen attached?

Answer 44

Anterior/frontal horn

Question 45

What a. runs thru the cavernous sinus?

Answer 45

ICA