Crenation

Crenation (from the Latin crenatus, scalloped or notched)

Crenated RBCs

The phenomenon of shrinking of cells when placed in a hypertonic environment (a hypertonic solution is one in which the concentration of solute is greater than that of the cells), as a result of osmosis (the diffusion of water across a semi-permeable membrane from a region of higher concentration to a region of lower concentration until dynamic equilibrium has been reached. Crenation is particularly noticable in red blood cells, which become scalloped and notched when placed in a hypertonic solution, losing their usual biconcae shape, and takng the appearance of a spiked ball, from which they take the name of echinocytes or burr cells.