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Protection of the Central Nervous System

The CNS is a vital system when it comes to allowing the human body to function. Even the smallest injury can result in terrible physical repercussions. Thus, the CNS is one of the best protected systems in the human body. The CNS is primarily protected by both by meninges and cerebrospinal fluid (CSF)



The three membranes that cover the brain and spinal cord.

The three layers are the dura mater, arachnoid, and pia mater

Dura mater- The thick superficial membrane of the meninges. It also serves at the internal periosteum in the cranium. In parts of the dura mater, the double layers are separated by sinuses, large blood vessels. The vessels are responsible for draining the blood that leaves the brain and directing it to the jugular veins.

The dura mater breaks up into four sections:

Falx Cerebri The most spacious of the four compartments.  The falx cerebri is located between the cerebral hemispheres.  It then attaches to the crista galli located on the ethmoid bone

Tentorium Cerebelli

The tentorium cerebelli is located between the cerebellum and the posterior section of the cerebrum
Epidural space The epidural space is located between the bone and the dura mater
Subdural space The subdural space functions to separate the dura mater from the arachnoid in the spinal cord and cranial areas of the human body


Arachnoid- is a thin medial layer of the dura mater. Arachnoid connects to the innermost layer of the dura mater, the pia mater by allowing projections to unite to two sections of the dura mater. In the area between the arachnoid and pia mater exists the subarachnoid space which houses cerebrospinal fluid.

Pia mater- is the thin and most deep layer of the dura mater. The Pia mater lies extremely close to the brain and outlines every detail of the concave and convex brain tissue.



The cerebrospinal fluid serves as a cushion to the floating brain. It consists of 99% water and a 1% mix of glucose, proteins, urea and salts. Around 135 mL of CSF surrounds fills the ventricles of the brain, and subarachnoid space surrounding the brain and spinal cord. Capillary networks called the choroids plexuses are responsible for producing the bulk of the bodies CSF supply. Once CSF is produced it circulates through the ventricles in an inferior motion. As the CSF enters each ventricle more fluid is added. The cerebrospinal fluid divides paths so that some travels superiorly to the brain while some moves inferiorly to fill the subarachnoid space. The cerebrospinal fluid then proceeds to be reabsorbed into the blood by means of arachnoid granulations. Arachnoid granulations protrude into the large sinuses present within the dura mater. The production and reabsorption processes occur at around the same rate to ensure homeostasis in the body.

The cerebrospinal fluid serves two main purposes in protecting the structures in the CNS. First, it is designed to cushion the delicate brain and spinal cord. Fluids do not compress to a large degree, thus when the head in jolted the cerebrospinal fluid is present to absorb the shock and prevent damage from direct contact with the cranial bones. It similarly protects the spinal cord from a direct collision with its bony encasement. CSF also functions to act as a mediator for the trade of nutrients and waste between the blood and the brain. Cerebrospinal fluid also dissolves and carries substances removed from the blood through filtration.


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