Epiphysis

An epiphysis (from Ancient Greek ἐπί (epí) 'on top of' and φύσις (phúsis) 'growth'; pl.: epiphyses) is one of the rounded ends or tips of a long bone that ossify from one or more secondary centers of ossification. Between the epiphysis and diaphysis (the long midsection of the long bone) lies the metaphysis, including the epiphyseal plate (growth plate). During formation of the secondary ossification center, vascular canals (epiphysial canals) stemming from the perichondrium invade the epiphysis, supplying nutrients to the developing secondary centers of ossification. At the joint, the epiphysis is covered with articular cartilage; below that covering is a zone similar to the epiphyseal plate, known as subchondral bone. The epiphysis is mostly found in mammals but it is also present in some lizards. However, the secondary center of ossification may have evolved multiple times, having been found in the Jurassic sphenodont Sapheosaurus as well as in the therapsid Niassodon mfumukasi. The epiphysis is filled with red bone marrow, which produces erythrocytes (red blood cells).