[3] The tela choroidea is a very thin part of the loose connective tissue of pia mater overlying and closely adhering to the ependyma.

[4][2] The tela choroidea in the ventricles forms from different parts of the roof plate in the development of the embryo.

The choroid fissure is C-shaped, runs between the fornix and the thalamus in the body of the ventricle, and between the stria terminalis and hippocampal fimbria in the inferior horn, and is the location of the attachment of the margins of the choroid plexus.

Two vascular fringes from the lower fold invaginate the roof and form the choroid plexus.

The anterior layer of the fold, contains vascular fringes which make up the choroid plexus.