Less protein
Different ion concentrations
Formed by choroids plexuses in the four ventricles of the brain
Are plexuses of capillaries that project into the lateral, third and fourth ventricles
Circulates through ventricular system
From lateral ventricles to interventricular foramina to third ventricle
From third ventricle through cerebral aqueduct to fourth ventricle
From fourth ventricle through paired lateral apertures and a single midline aperture in the roof into subarachnoid space
Absorbed through arachnoid granulations into venous blood in dural venous sinuses
Arachnoid granulations are tufts of arachnoid villi protruding into the dural venous sinuses
Subarachnoid space with CSF extends into core of the tufts
Approximately 400 mL/day of CSF → venous circulationpage 70
page 71Vasculature of dura
Primarily provides blood to calvaria
Middle meningeal artery
Branch of axillary artery
Enters through foramen spinosum
Has anterior and posterior branches
Meningeal branches of
Ophthalmic arteries
Occipital arteries
Vertebral arteries
Venous drainage: meningeal veins
Accompany meningeal arteries
Occur in pairs
Frequently torn in skull fractures
Middle meningeal veins drain to pterygoid venous plexus