1. Meninges/CSF

Meninges are derived from mesoderm.

Three meninges

1. Cranial dura

Structures formed by

1. septa (falx cerebri, tentorium cerebelli, falx cerebelli, diaphragma sellae)

2. venous sinuses (CSF returned, venous drainage)

a. SSS, between endosteal and meningeal layers

b. ISS, between two meningeal layers

c. Straight sinus (infection)

d. transverse sinus

e. sigmoid sinus

f. confluence of sinuses

g. cavernous sinuses (infection)

tentorial incisure = tentorial notch (midbrain fits through)

a. endosteal layer

not continuous with spinal cord dura

b. meningeal layer

continuous with spinal cord dura

2. Arachnoid dura

forms subdural space with dura mater (potential space)

subarachnoid space (trabeculae, CSF, all major blood vessels of the brain, continuous with ventricular systems)

arachnoid villi: protrude into sinuses (SSS)

cisterns = enlarged subarachnoid spaces

1. cisterna magna (over cerebellum and medulla)

2. pontine cistern

3. interpeduncular cistern

4. lumbar cistern

3. Pia mater

thin, vascular, covers ventricles

blood vessels run in subarachnoid space on surface of pia

part of choroid plexus = tela choroidea (pia) + ependyma (epithelium)

CSF

Formed in lateral and 4^th ventricles

lateral ventricles à interventricular foramen of Monro à 3^rd ventricle à aqueduct of Sylvius à 4^th ventricle à lateral foramina of Luschka and medial formanen of Magendie

Composition

· protein (15-45mg/100ml)

· glucose (40-80mg/100ml)

· cells (0-5 lymphocytes/mm³)

· pressure (50-150mmH₂O)

· volume (125-175ml)

· Relative to blood:

o more Na+ and Cl-

o less glucose and K+

o little protein