Definition of Pinosome

Pinosome: A tiny fluid-filled vesicle (bubble) within a cell.

Pinosomes are created in the process of pinocytosis in which tiny incuppings called caveolae (little caves) in the surface of the cell close and then pinch off to form pinosomes within the cytoplasm of the cell.

Pinocytosis permits the active transport of fluid through the membrane surrounding the cell into the interior of the cell.

The word "pinosome" stemmed from Greek roots: pinein, to drink + soma, body = a drinking body.