ventricle

https://doi.org/10.1351/goldbook.12163
Normal cavity within an organ, as in the brain or heart.
Notes:
  1. In the brain there are two lateral ventricles and two midline (called the third and fourth) ventricles.
  2. The ventricles in the brain are filled with, and produce most of, the cerebrospinal fluid, and play a critical role in its circulation.
Source:
PAC, 2015, 87, 841. (IUPAC Glossary of terms used in neurotoxicology (IUPAC Recommendations 2015)) on page 915 [Terms] [Paper]