epiphysiss

Epiphysis is the term used for the end part of a long bone, where it forms a joint with adjacent bones. The spelling epiphysiss is not standard; the correct singular is epiphysis and the plural is epiphyses. The epiphysis is distinct from the diaphysis (the shaft) and the metaphysis, which lies between the epiphysis and the diaphysis.

In growing bones the epiphysis is separated from the diaphysis by the metaphysis and the growth occurs at the epiphyseal plate (physis), a band of hyaline cartilage within the metaphysis near the epiphysis. This growth plate adds length to the bone through endochondral ossification. In adults, the epiphyseal plate typically ossifies, leaving an epiphyseal line where growth once occurred.

Anatomically, each epiphysis is typically capped by articular cartilage, a thin layer of hyaline cartilage that covers the joint surface. The interior is largely cancellous (spongy) bone with a cortex of compact bone surrounding it. Red bone marrow may be present in the spongy bone of the epiphysis, contributing to hematopoiesis in some bones.

Functionally, the epiphysis contributes to joint stability and movement by forming articulated surfaces with adjacent bones. The spongy bone within the epiphysis helps absorb impact, while the surrounding cartilage reduces friction in the joint.

Clinical notes: epiphyseal injuries are common in children and are classified by the Salter-Harris system, reflecting potential disruption of the growth plate and subsequent effects on bone growth. Proper assessment is important to prevent growth disturbances.

See also: bone anatomy, metaphysis, diaphysis, growth plate.