Choroid plexus of lateral ventricle

The choroid plexus of the lateral ventricle is a vascular fold that projects into the ventricular cavity and produces cerebrospinal fluid (CSF). It consists of fenestrated capillaries within connective tissue, covered by specialized choroid epithelial cells. Tight junctions between these epithelial cells form the blood–CSF barrier.

Relationship to the choroid fissure

The key to understanding how the plexus reaches the ventricle is the choroidal fissure. This is a narrow, C-shaped cleft in the medial part of the lateral ventricle. At this site, vascular pia forming the tela choroidea invaginates the ventricular wall, pushing the ventricular epithelial covering in front of it. The resulting vascular, epithelial-covered fold projects into the ventricular lumen as the choroid plexus.

--- Body of lateral ventricle

In the body of the lateral ventricle, the choroidal fissure lies between the fornix medially and the thalamus/lamina affixa laterally. The tela choroidea is attached to these margins at the taenia fornicis and taenia choroidea, respectively, and the choroid plexus projects from this tela into the ventricular cavity.

A simple medial-to-lateral arrangement is: Fornix → taenia fornicis → choroidal fissure + tela/choroid plexus → taenia choroidea → thalamus

--- Temporal horn of lateral ventricle

As the lateral ventricle curves inferiorly, the choroidal fissure continues into the temporal horn. Here, the lower margin of the choroid plexus of lateral ventricle is related to the fimbria of the hippocampus, while its upper margin is related to the roof/diencephalic attachment of the temporal horn. The vascular tela again invaginates at this fissure, producing the choroid plexus of the temporal horn.

Therefore, the same basic arrangement occurs in both regions: the choroidal fissure provides the line along which vascular tela invaginates the ventricular wall and forms the choroid plexus. The plexus consequently follows a C-shaped course through the body, atrium and temporal horn of the lateral ventricle.