Epiphysis

EPIPHYSIS, epiphysis, a term used to denote the end of a long (tubular) bone. In long bones, one distinguishes the middle part—the body, or diaphysis (see) (diaphysis), and two end sections, or epiphyses (proximal and distal); bony outgrowths are given the special name of apophyses (see). At an early stage of skeletal development, epiphyses consist of cartilaginous tissue; the process of their ossification begins later than the ossification of the diaphyses. In the epiphysis, so-called endochondral ossification (see Ossification, Skeleton) takes place. Inside the cartilaginous primordium of the epiphysis, an independent ossification center appears. The appearance of ossification centers in the cartilaginous epiphyses of various long bones is observed at different times. The first ossification center to form is in the distal epiphysis of the femur (in the 9th fetal month). This fact is usually taken into account in forensic medical practice as one of the important signs of fetal maturity. After the ossification of the epiphysis, cartilaginous tissue persists for a long period of time (varying for different bones) at the border between it and the diaphysis of the bone in the form of the so-called epiphyseal cartilage (cartilago epiphysaria) (see Ossification, Bone). Epiphyseal cartilages play an important role in the processes of bone growth in length. In the period between 13 and 24 years of age, the disappearance of the epiphyseal cartilages and the formation of synostoses between the epiphyses and the diaphyses of long bones occur. The only remnants of the cartilaginous epiphysis are the cartilaginous covering on the surface participating in the formation of a joint. The epiphyses of formed bones consist almost entirely of spongy bone substance (substantia spongiosa); a thin layer of compact substance covers only the surface of the epiphysis. The structure of the spongy substance of the epiphyses of various bones of the skeleton has a different character, depending on the functional significance of one or another part of the skeleton. The spongy substance at the border between the epiphysis and the diaphysis is designated by a special term—metaphysis (metaphysis). In childhood, detachments or separations of the epiphysis are observed, a phenomenon of so-called epiphysiolysis (see Fractures). The study of the structure of the epiphysis in anatomy is carried out by methods of clearing, radiography, and the preparation of bone sections or ground sections. The term "epiphysis" is also used as a synonym for the pineal gland, epiphysis cerebri (see Pineal gland).

B. U.