Human Anatomy - M.M. Kurepina, A.P. Ozhigova, A.A. Nikitina 2010

Nervous system
General overview of the nervous system
Production and circulation of cerebrospinal fluid

The subarachnoid space contains CEREBROSPINAL FLUID, which is chemically a modified interstitial fluid. This fluid acts as a Shock absorber for Brain tissue. It is also distributed along the entire length of the spinal canal and within the ventricles of the brain. Cerebrospinal fluid is secreted into the cerebral ventricles by the choroid plexuses, which are formed by numerous capillaries branching from arterioles and hanging like tufts into the ventricular cavity (Fig. 3.4). The surface of the plexus is covered by a simple cuboidal epithelium derived from the ependyma of the neural tube. Beneath the epithelium lies a thin layer of Connective Tissue originating from the pia and arachnoid mater.

Cerebrospinal fluid flows from the Lateral ventricles through the Third ventricle and the cerebral aqueduct to the Fourth ventricle. From there, it drains through apertures in the roof of the ventricle into the subarachnoid space. If the outflow of fluid is obstructed for any reason, an excess builds up in the ventricles, causing them to dilate and compress the brain tissue. This condition is known as internal Hydrocephalus.

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Fig. 3.4. Diagram of cerebrospinal fluid formation:

1 — superior sagittal sinus; 2 — arachnoid granulation; 3 — dura mater; 4 — Forebrain; 5 — choroid plexus; 6 — subarachnoid space; 7 — lateral ventricle; 8 — Diencephalon; 9 — Midbrain; 10 — Cerebellum; 11 — Medulla Oblongata; 12 — lateral aperture of the fourth ventricle; 13 — periosteum of the vertebra; 14 — vertebra; 15 — intervertebral foramen; 16 — epidural space; 17 — descending flow of cerebrospinal fluid; 18 — Spinal Cord; 19 — pia mater; 20 — dura mater; 21 — fluid exchange between spinal cord tissue and the subarachnoid space; 22 — filum terminale; 23 — coccyx; 24 — arachnoid mater; 25 — spinal ganglion; 26 — dura mater transitioning into perineurium; 27 — spinal nerve; 28 — vein of the vertebral plexus; 29 — cerebrospinal fluid entering venules of the pia mater; 30 — choroid plexus of the fourth ventricle; 31 — arachnoid mater; 32 — pia mater; 33 — transverse sinus with arachnoid granulation; 34 — Vessels of the pia mater; 35 — cerebral Veins

Cerebrospinal fluid is also formed by Blood Vessels penetrating the brain. The amount of this fluid is small; it is released onto the surface of the brain along the pia mater that accompanies the vessels. From the brain surface, cerebrospinal fluid is reabsorbed back into the bloodstream through arachnoid granulations—arachnoid villi protruding into the dural sinuses. Through the thin lining of the villi, cerebrospinal fluid enters the venous blood of the sinus. There are no Lymphatic vessels in the BRAIN AND SPINAL cord.