CSF is produced by the choroid plexus within the ventricles. Which structure is primarily responsible for CSF production?

• A. Ependymal cells
• B. Pineal gland
• C. Arachnoid granulations
• D. Choroid plexus

Answer: (D)

CSF production comes from the choroid plexus, a specialized network inside the ventricles formed by capillaries wrapped in ependymal cells. These cells actively transport ions and water from the blood, creating a filtrate that becomes CSF. The choroid plexus is highly vascularized and designed for secretion, so it drives most CSF formation (roughly a half-liter per day). The ependymal lining helps move CSF and maintains the barrier between blood and CSF, but it’s the choroid plexus’s secretory activity that makes it the primary source. The pineal gland is an endocrine organ and not involved in CSF production, and arachnoid granulations are for CSF absorption into the venous system, not production.