Cristae

(1) In anatomy, cristae are bony projections in vertebrate animals and man that serve to attach muscle tendons to the bones.

(2) In cytology, cristae are folds that protrude into the cavities of mitochondria and partially partition them. Cristae substantially increase the inner surface of the mitochondria. They are probably formed from processes of the inner membrane. In spherical mitochondria the cristae are oriented radially; in elongated ones they are most often perpendicular to the longitudinal axis. The thickness of the cristae is about 160 angstroms. A direct relationship is thought to exist between the number of cristae and the activity of oxidative processes in the mitochondria. The number of cristae in different cells varies. For example, the mitochondria of liver cells contain few cristae, and heart muscle cells have many cristae. The mitochondria of many tissues have few cristae in the early stages of embryogeny, but with an increase in energy metabolism their number increases. The number of cristae also changes under the influence of various factors (shifts in osmotic pressure and temperature, narcotics).