Question

cerebrospinal fluid is secreted by choroid plexuses in the ventricles and reabsorbed by arachnoid granulations in the _______

reticular formation
substantia nigra
superior sagittal sinus
tegmentum
central canal of the spinal cord

Explanation:

Identify the physiological process

The question asks about the site where cerebrospinal fluid (CSF) is reabsorbed into the venous circulation after being secreted by the choroid plexuses.

Analyze the role of arachnoid granulations

Arachnoid granulations (or arachnoid villi) are small protrusions of the arachnoid mater that project through the dura mater into the dural venous sinuses. They allow CSF to exit the subarachnoid space and enter the bloodstream.

Evaluate the given anatomical structures

• reticular formation: A network of pathways in the brainstem involved in sleep-wake cycles and consciousness.
• substantia nigra: A basal ganglia structure located in the midbrain, critical for dopamine production and movement control.
• superior sagittal sinus: A major dural venous sinus running along the longitudinal fissure where arachnoid granulations primarily project to return CSF to venous blood.
• tegmentum: A general area within the brainstem.
• central canal of the spinal cord: A narrow space running longitudinally through the length of the spinal cord containing CSF, but not a site of reabsorption via arachnoid granulations.

Determine the correct anatomical site

The arachnoid granulations project predominantly into the superior sagittal sinus, making it the primary site of CSF reabsorption.

Answer:

• reticular formation
• substantia nigra
• superior sagittal sinus (Correct answer)
• tegmentum
• central canal of the spinal cord