choroid plexus

https://doi.org/10.1351/goldbook.10521

Infoldings of blood vessels of the pia mater, projecting into the cerebral ventricles, covered with ependymal cells, and secreting cerebrospinal fluid.

Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 735 [Terms] [Paper]