Meningeal coverings, ventricles, and CSF

Question 1

What are the three meningeal coverings of the brain?

Answer 1

Dura, arachnoid, and pia

Question 2

Describe the dura mater layers

Answer 2

Outer periosteal layer: firmly attached to the skull, contains the meningeal arteries
Inner meningeal layer: in close contact with the arachnoid and continuous with spinal dura
In the spinal area, it is single layered and suspended in the vertabreal canal.

Question 3

What is important about the cranial epidural space and spinal epidural space?

Answer 3

Cranial is a potential space that only exists and becomes filled with fluid during pathalogical conditions. Spinal is real space between dura and vertebral periosteum

Question 4

What are the dural folds?

Answer 4

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

Question 5

What are the dural venous sinuses?

Answer 5

Endothelial lined spaces between the periosteal and the inner meningeal layers of the dura mater that lead to the jugular veins

1. Superior sagittal
2. Inferior sagittal
3. Straight
4. Occipital
5. Confluence of sinuses
6. Transverse
7. Sigmoid (right and left)
8. Cavernous (paired)
9. Intercavernous
10. Sphenoparietal (paired)
11. Superior petrosal (paired)
12. Inferior petrosal (paired)
13. Basilar

Question 6

Inflammation like meningitis or traction by an expanding mass can cause headache-why?

Answer 6

The dura and some subarachnoid blood vessels are pain sensitive structures

Question 7

What is the role of emissary veins?

Answer 7

They connect the extracranial veins to the venous sinuses inside the cranium, and are an important route for the spread of infection

Question 8

What space is the CSF in?

Answer 8

he subarachnoid space

Question 9

What are two important components of arachnoid mater?

Answer 9

Arachnoid trabeculae (suspends the brain)
Arachnoid granulations/villi: outpouchings of the aracnhoid mater which poke through holes in the walls of venous sinouses, allows CSF to pass uni-directionally to the venous sinuses.

Question 10

What is the arachnoid barrier?

Answer 10

A layer of cells that are connected to each other by bands of tight junctions. This forms a barrier to the diffusion of extracellular substances from the dura into CSF, or in the reverse direction

Question 11

How is the pia mater attached?

Answer 11

It is attached on one side to arachnoid trabeculae and on the other to astrocyte feet that carpet the surface of the CNS

Question 12

The pia gives off what two structures?

Answer 12

Denticulate ligaments and filum terminale

Question 13

At what level do the spinal dura and arachnoid end?

Answer 13

S2

Question 14

What causes epidural bleeding?

Answer 14

Tearing a meningeal artery, typically as the result of a skull fracture

Question 15

What causes subdural bleeding?

Answer 15

Tearing a cerebral vein as it penetrates the arachnoid on its way into a venous sinus

Question 16

What causes subarachnoid bleeding?

Answer 16

Rupture of a cerebral artery (burst aneurysm)

Question 17

What kind of hematoma does a dural venous sinus injury cause?

Answer 17

epidural or subdural hematoma

Question 18

What are the ventricles of the brain?

Answer 18

1. a pair of lateral ventricles in the telecephalon (one for each cerebral hemisphere)
2. A midline third ventricle (cavity of the diencephalon)
3. A midline fourth ventricle (cavity of the rhombencephalon)

Question 19

Describe the ventricle map

Answer 19

Two lateral ventricles –> two interventricular foramina of Monro –> third ventricle –> aqueduct of Silvius –> fourth ventricle –> median aperature (foramen of mramen of magendiea) and two lateral aperatures (foramina of luschka) to the subarachnoid space

Question 20

What is the rate of formation of CSF? Total volume?

Answer 20

500 mL/day

90 to 150 mL (23 in ventricles and remaining is subarachnoid space)

Question 21

Describe the nature of the movement of CSF across the arachnoid villi

Answer 21

it is passive, driven by the difference in hydrostatic pressure between the CSF in the subarachnoid space adn the venous blood in the superior sagittal sinus. The villi act like tiny flap valves so that reverse flow is prevented if venous pressure exceeds CSF pressure

Question 22

What is the choroid plexus?

Answer 22

the joining of the inner lining of the ventricle and the outer covering of the CNS without any intervening neural tissue. Located at lateral ventricle, roof of third ventricle, roof of fourth ventricle

Question 23

What is the choroid epithelium?

Answer 23

Ependymal cells in the choroid plexus that are specialized as a secretory epithelium. Adjaecnt cells are joined by tight junctions, forming a diffusion barrier.

Question 24

What are subarachnoid cisterns?

Answer 24

Large parts of subarachnoid space, corresponding to major irregularities in the surface of the CNS. Cisterna magna is an important one

Question 25

What are the functions of CSF?

Answer 25

Mechanical support, cushioning effects, dampens effects of trauma, vehicle for removal of metabolites, route for spread of neuroactive hormones

Question 26

Describe CSF composition

Answer 26

Very little protein. Less glucose, ca2+, and K+ ions than serum. More Na+, Cl-, and Mg2+ ions than serum.

Question 27

What is hydrocephalus?

Answer 27

Dilation of the ventricles with increased intracranial pressure that occurs when circulation of the CSF is blocked or its absorption impeded

Question 28

What are the two types of hydrocephalus?

Answer 28

Non communicating: obstruction of flow in ventricular system

communicating: impaired CSF absoprtion in arachnoid granulations, obstruct of flow in the subarachnoid space

Question 29

What is the composition of circumventricular organs?

Answer 29

neurons, glia, ependymal cells, leptomeningeal and vascular elements. Around the 3rd and 4th ventricles and lack a BBB (fenestrated capillaries)

Question 30

What is the role of circumventricular organs?

Answer 30

sodium/water balance, CV regulation, energy metabolism, and immunomodulation