Meninges, Ventricles, CSF

Question 1

what are leptomeninges

Answer 1

arachnoid and pia

Question 2

what is the only layer that is not continuous with the spinal meninges

Answer 2

outer dura

Question 3

2 layers of dura mater

Answer 3

outer periosteal layer - attached to skull; contains meningeal arteries

inner meningeal layer - contact with arachnoid; continuous

Question 4

dural folds

Answer 4

projections that separate parts of the brain to prevent displacement of the brain during head movement; shock cushioning

Question 5

what are the 4 dural folds

Answer 5

1. falx cerebri - longitudinal; divides cerebral hemispheres
2. tentorium cerebelli - horizontal; separates cerebrum and cerebellum
   => tentorial notch - brainstem exits
3. falx cerebelli - separates cerebellar hemispheres
4. diaphragma sellae - covers sella turcica

Question 6

NAME the dural venous sinuses (endothelial lined spaces eventually leading to the internal jugular

Answer 6

• superior sagittal (upper border of falx)
• inferior sagittal (lower border of falx)
• straight (junction of falx and tentorium)
• occipital
• confluence of sinuses (straight, superior, and occipital)
• transverse (2 - each side)
• sigmoid (2)
• cavernous (2)
• intercavernous (crosses sella turcica)
• sphenoparietal
• superior petrosal
• inferior petrosal
• basilar

Question 7

emissary veins

Answer 7

connect extracranial veins (outside the skull) to dural venous sinuses
- route of infection from skin and scalp

Question 8

arachnoid mater spaces

Answer 8

subdural - between dura and arachnoid

subarachnoid - between arachnoid and pia; contains CSF

Question 9

arachnoid trabeculae

Answer 9

threads of arachnoid mater that go through the subarachnoid space to the pia

Question 10

arachnoid villi/granulations

Answer 10

CSF passes to the venous sinuses through these (ONE WAY PASSAGE)

Question 11

arachnoid barrier

Answer 11

tight junctions cell layer preventing diffusion between dura and CSF

Question 12

pia mater

Answer 12

• delicate, vascular
• attached to arachnoid trabeculae and astrocyte endfeet
• forms choroid plexus

Question 13

difference between cranial and spinal meninges

Answer 13

• spinal epidural space: filled with CT and venous ==> DOES NOT EXIST in cranium (only a potential space for fluid buildup in pathological conditions)
• denticulate ligaments between pia to arachnoid

Question 14

epidural hematoma

Answer 14

• tear in meningeal artery
• possible cause: fracture of skull
• pushes dura away from skull ==> creates epidural space

Question 15

subarachnoid hemorrhage

Answer 15

• rupture of cerebral artery

- cause: aneurysm

Question 16

subdural bleeding

Answer 16

• tearing cerebral vein a it penetrates the arachnoid to the venous sinus
• causes separation of inner layer of dura from arachnoid

Question 17

lateral ventricles

Answer 17

• telencephalon
• 2 - each hemisphere
• components:
  => anterior horn
  => body (parietal)
  => posterior horn (occipital)
  => inferior horn (temporal lobe)
  => atrium - where body and inferior meet

Question 18

how to lateral and 3rd ventricles connect

Answer 18

foramina of monro

Question 19

third ventricle

Answer 19

• diencephalon

- medial surface of thalamus

Question 20

how do 3rd and 4th ventricles connect

Answer 20

cerebral aqueduct of Sylvius

Question 21

fourth ventricle

Answer 21

• rhombencephalon
• central canal from spinal cord extends from here
• CSF flows out here

Question 22

how does CSF leave the 4th ventricle

Answer 22

2 lateral apertures (foramina of Luschka)

1 medial aperture (foramen of Magendie)

Question 23

CSF

Answer 23

• clear
• secreted by choroid plexus
• subarachnoid, ventricles, brain, spinal cord
• 500mL/day made
• 23mL in ventricles

Question 24

choroid plexus

Answer 24

• invaginations of vascular tissue, pia mater, and ependymal lining
• choroid epithelium: specialized ependymal cells
• where: ventricles
• multiple folds

Question 25

CSF circulation route

Answer 25

lateral ventricles => interventricular foramina of Monro => 3rd vent. => aqueduct of sylvius => 4th vent. => lateral foramina of Luschka/medial foramen of Magendie => cisterna magna (cerebellomedullary) => subarachnoid, brain, spinal cord (descends through spinal subarachnoid, ascends in ventral spinal cord, travels rostrally over the front hemisphere) => arachnoid villi => superior sagittal sinus

Question 26

CSF function

Answer 26

- cushioning - removal of metabolites - spread hormones - reduce traction - intercranial pressure maintenance

Question 27

CSF composition

Answer 27

- little protein - less than serum: glucose, Ca2+, K+ - more than serum: Na+, Cl-, Mg2+

Question 28

noncommunicating hydrocephalus

Answer 28

- cuts off communication to another part of the ventricular system - occlusion of foramina, apertures, or aqueduct

Question 29

communicating hydrocephalus

Answer 29

- obstruction of tentorial notch or arachnoid villi | - can't be absorbed into sinuses

Question 30

circumventricular organs

Answer 30

- lack BBB - chemo affects brain - no tight junctions - fenestrated capillaries

Question 31

sensory circumventricular organs

Answer 31

area postrema subfornical organ organum vasculosum lamina terminalis

Question 32

secretory circumventricular organs

Answer 32

neurohypophysis (posterior pituitary) | median eminence

Question 33

other circumventricular organs

Answer 33

pineal | subcommissural