choroid plexus
Summary
The choroid plexus is a highly vascularized structure in the brain ventricles that produces cerebrospinal fluid (CSF). It consists of specialized ependymal cells and fenestrated capillaries that form the blood-CSF barrier, producing approximately 500-600 mL of CSF daily through active secretion and ultrafiltration.
Detail
The choroid plexus is located in all four ventricles of the brain, with the largest portions in the lateral and fourth ventricles. Structurally, it consists of a core of fenestrated capillaries surrounded by cuboidal epithelial cells (specialized ependymal cells) connected by tight junctions. These tight junctions form the blood-CSF barrier, which is distinct from the blood-brain barrier. The choroid plexus actively secretes CSF through Na+/K+-ATPase pumps and carbonic anhydrase activity, creating an osmotic gradient that drives fluid production. CSF production is largely independent of intracranial pressure until very high pressures are reached. The choroid plexus also serves as a route for immune surveillance of the CNS and can be a site of infection entry. Clinically, choroid plexus papillomas (benign) and carcinomas (malignant) can cause hydrocephalus due to CSF overproduction or obstruction. The choroid plexus is also involved in drug transport and metabolism, expressing various transporters that can affect CNS drug penetration.
Sources
- Netter's Atlas of Human Anatomy
- Kandel's Principles of Neural Science
- First Aid for the USMLE Step 1
- Gray's Anatomy
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