Meninges & Ventricular System

Question 1

Function of Meninges

Answer 1

• provides protective barrier that safeguards the brain and spinal cord against trauma
• stabilizes the shape and position of the brain during head movements
• stabilizes by (1) mechanically suspending the brain within meninges which are anchored to skull, (2) CSF creates buoyant environment to decrease the effects of gravity

Question 2

Dura mater

Answer 2

• outer periosteal layer and inner meningeal layer (around brain, not spinal cord)
• meningeal layer extends far into cranial cavity at falx cerebri & tentorium cerebelli
• loosely adheres to surface of the CNS

Question 3

Arachnoid

Answer 3

• adheres to the inner surface of the dura
• CSF percolates within the arachnoid over the surface of the brain and spinal cord
• loosely adheres to the surface of the CNS

Question 4

Pia mater

Answer 4

thin layer of cells that tightly adheres to the surface of the brain (follows along all gyri and extends into the depth of the sulci

Question 5

epidural space

Answer 5

potential space between inner surface of skull and tightly adherent dura

Question 6

subdural space

Answer 6

potential space between inner layer of dura and the loosely adherent arachnoid

Question 7

subarachnoid space

Answer 7

true space between arachnoid and pia (filled with CSF)

Question 8

sinuses

Answer 8

true space between the two layers of the dura at distinct regions of the brain (i.e. superior sagittal sinus)
- conduits for venous drainage from the cerebral hemispheres and CSF from subarachnoid space

Question 9

cisterns

Answer 9

true space between the two layers of the dura at distinct regions of the brain (i.e. cisterna magna)
- filled with cerebral spinal fluid

Question 10

cerebrospinal fluid

Answer 10

• 70% produced in choroid plexus, 30% secreted by parenchyma in brain
• 500 ml produced per day
• total volume = 90-140ml, 100ml in subarachnoid space
• filtrates blood as it passes through choroid plexus
• has low protein content
• clear, colorless, sterile
• presence of white blood cells indicates bacteria meningitis or viral encephalitis

Question 11

Ventricles (functions)

Answer 11

• brain and spinal cord float in CSF > reduces tension bw CNS and connecting nerves and blood vessels
• provides cushion that dampens the effect of trauma
• acts as a vehicle to remove metabolites from CNS
• stabilizes ionic composition of CNS

Question 12

Acquired Hydrocephalus

Answer 12

develops after birth as a result of neurological conditions such as head trauma, brain tumor, cyst, intraventricular hemorrhage or infection of CNS

Question 13

congenital hydrocephalus

Answer 13

present at birth, caused by complex interaction of genetic and environmental factors during fetal development

Question 14

non obstructive (communicating) hydrocephalus

Answer 14

• functional impairment of the arachnoid granulations
• causes include: intraventricular hemorrhage, meningitis, head injury, brain tumor (back of head) & congenital absence of arachnoidal granulations

Question 15

obstructive (non-communicating) hydrocephalus

Answer 15

CSF-flow obstruction of the interventricular foramen, cerebral aquaduct, foramina of luschka and/or foramina of magendie
- caused by tumors, cysts, congenital

Question 16

epidural hematoma

Answer 16

caused by structural disruption of the dural and skull blood vessels
- laceration of the middle meningeal artery is most common etiology

Question 17

subdural hematoma

Answer 17

• chronic > caused by rupture in the bridging veins
• acute > caused by rupture in bridging veins immediately after an injury where impact velocity is high