growth plate

Epiphyseal plate

The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a hyaline cartilage plate in the metaphyses of children and adolescents.

Anatomy & Development

Epiphyseal plates are present in growing bones. They are found in children and are present through puberty and early adulthood. These plates are located at one or both ends of bones between the epiphysis (end) and the diaphysis (shaft) of long bones. Growth occurs towards the diaphysis or shaft of the long bone. In most adults, the epiphyseal plates ossify by the mid twenties and growth arrests.

Role in Bone Elongation

Whereas endochondral ossification is responsible for the initial bone development from cartilage in utero and infants, the epiphyseal plate is responsible for longitudinal growth of bones. The plate's chondrocytes are under constant division by mitosis. These daughter cells stack facing the epiphysis while the older cells are pushed towards the diaphysis. As the older chondrocytes degenerate, osteoblasts ossify the remains to form new bone. Around the end of puberty, the epiphyseal cartilage cells stop duplicating and the entire cartilage is slowly replaced by bone, leaving only a thin epiphyseal line. Once the adult stage is reached, the only way to manipulate height is modifying bone length via distraction osteogenesis.

The growth plate has a very specific morphology in having a zonal arrangement. The growth plate includes a relatively inactive reserve zone at the epiphyseal end, moving distally into a proliferative and then hyper trophic zone and ending with a band of ossifying cartilage (the metaphysis). The growth plate is clinically relevant in that it is often the primary site for infection, metastasis, fractures and the effects of endocrine bone disorders.

Pathology

Defects in the development and continued division of epiphyseal plates can lead to growth disorders. The most common defect is achondroplasia, where there is a defect in cartilage formation. Achondroplasia is the most common cause of dwarfism.

Salter-Harris fractures can occur on epiphyseal plates.

Studies in Animals

John Hunter studied growing chickens. He observed bones grew at the ends and thus demonstrated the existence of the epiphyseal plates. Hunter is considered the "father of the growth plate".

References

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