Epiphysis
The epiphysis is the rounded end of a long bone, at its joint with adjacent bone(s). Between the epiphysis and diaphysis (the long midsection of the long bone) lies the metaphysis, including the epiphyseal plate (growth plate). 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 (see Wiktionary:subchondral).
The epiphysis is filled with red bone marrow, which produces erythrocytes (red blood cells).
Types
There are four types of epiphysis:
- Pressure epiphyses: These epiphyses are articular that is they take part in joint formation. These epiphyses are the weight transmitting epiphyses. Examples are head of the humerus, lower end of the radius etc.
- Traction epiphyses: These are non-articular and do not take part in the formation of joints. They also do not take part in transmission of weight. The actual job of traction epiphyses is to provide attachment to tendons of muscles. The traction epiphyses ossify later than the pressure epiphyses. Examples of these epiphyses are tubercles of humerus (greater tubercle and lesser tubercle) and trochanters of femur (greater trochanter and lesser trochanter)
- Atavistic epiphyses: These epiphyses are phylogenetically independent but they become fused in man. Examples are coracoid process of scapula and os trigonum.
- Aberrant epiphyses: As the name indicates (aberrant = not usual) these epiphyses are not always present. Examples are epiphyses at the head of the first metacarpal bone and at the base of other metacarpal bones.
Pathology
Pathologies of the epiphysis include avascular necrosis and osteochondritis dissecans (OCD). OCD involves the subchondral bone.
Epiphyseal lesions include chondroblastoma and giant-cell tumor.[1]
Additional images
References
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anat(c/f/k/f, u, t/p, l)/phys/devp/cell
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noco/cong/tumr, sysi/epon, injr
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