Question

Describe the route of CSF circulation in the mammalian brain

A) CSF is produced in the ventricles and circulates through the subarachnoid space, returning to the ventricles
B) CSF circulates from the lateral ventricles to the third ventricle, then to the fourth ventricle and subarachnoid space
C) CSF flows from the fourth ventricle to the lateral ventricles, then into the central canal of the spinal cord
D) CSF is produced in the subarachnoid space and absorbed into the ventricles

Answer 1

CSF is produced by the choroid plexus within the four ventricles and flows from the lateral ventricles to the third and fourth ventricles and then into the subarachnoid space, ending with reabsorption into the venous system through arachnoid granulations. The correct option is B.

Step-by-step explanation:

The circulation of cerebrospinal fluid (CSF) begins with its production in the choroid plexus of the four ventricles. From the lateral ventricles, CSF flows into the third ventricle via the interventricular foramina (also known as the foramina of Monro). In the third ventricle, additional CSF is produced, and then the fluid flows through the cerebral aqueduct into the fourth ventricle.

Within the fourth ventricle, more CSF is added to the circulating volume. The fourth ventricle connects to the subarachnoid space via a median aperture and two lateral apertures, allowing CSF to flow around the outside of the central nervous system (CNS).

CSF also travels into the central canal of the spinal cord, but this passage serves primarily as a cul-de-sac. The principal flow of CSF is into the subarachnoid space, where the fluid circulates around the brain and spinal cord.

Finally, CSF is reabsorbed into the venous blood through arachnoid granulations which protrude into the dural sinuses. This process of production and reabsorption is continuous, ensuring the movement of approximately 500 milliliters of CSF daily, thus maintaining optimal conditions for the nervous tissue.