07.3C U7P2 (PART C) Central Nervous System (Protection)

Meninges (Types)

Dura mater
Arachnoid mater
Pia mater

Meninges (Description)

Three layers of connective tissue which surround and protect the brain and spinal cord

Central Nervous System Layers of Protection

Scalp and skin
Skull and vertebral column
Meninges
Cerebrospinal fluid
Blood brain barrier

Dura mater

Double-layered external covering
Periosteum is attached to surface of the skull
Meningeal layer is the outer covering of the brain
Folds inward
Toughest layer
Translates as "tough mother"

Arachnoid mater

Middle layer of protective connective tissue that surrounds the brain and spinal cord; web-like, spongy

Pia mater

Internal layer of protective connective tissue that clings to the surface of the brain
Translates as "gentle mother"

Cerebral spinal fluid

A fluid formed by the choroid plexus that provides a watery cushion to protect the brain
Circulates in arachnoid space, ventricles, and central canal of the spinal cord
Similar to blood plasma composition
Sinus cavity of dura mater is filled with capillaries from arachnoid mater that reabsorb CSF
Only have about ½ cup circulating at a time

Blood brain barrier

Includes the least permeable capillaries of the body; specialized endothelial cells called astrocytes that surround the capillaries have many tight junctions that exclude many potentially harmful substances; permeable to small, nonpolar molecules such as:

- fats and fat soluble molecules
- respiratory gases
- alcohol
- nicotine
- anesthesia

Choroid plexus (Function)

A highly vascular portion of the lining of the ventricles that is made up of ependymal cells which secrete cerebrospinal fluid

Cerebral aqueduct

Connects 3rd and 4th ventricle

Subarachnoid space

A space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid and capillaries that make up the blood brain barrier

3rd ventricle of brain (Location)

Ventricle found in the diencephalon

4th ventricle of brain (Location)

Ventricle found between the brainstem and cerebellum

Lateral ventricles of brain (Location)

Ventricles found in each cerebral hemisphere

Ventricles of the brain

Four cavities found in the brain that contain cerebrospinal fluid