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Lengthening of long Bones

The epiphyseal plate is the area of growth in a long bone. The is a great of hyaline cartilage whereby ossification wake up in immature bones. Top top the epiphyseal next of the epiphyseal plate, cartilage is formed. On the diaphyseal side, cartilage is ossified, allowing the diaphysis to grow in length. The metaphysis is the wide portion of a lengthy bone between the epiphysis and the small diaphysis. The is taken into consideration a part of the growth plate: the part of the bone that grows during childhood, which, as it grows, ossifies close to the diaphysis and also the epiphyses.

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The epiphyseal plate is created of 4 zones that cells and activity.

The reserve zone, the an ar closest to the epiphyseal finish of the plate, contains little chondrocytes in ~ the matrix. This chondrocytes execute not participate in bone growth; instead, they secure the epiphyseal plate come the osseous organization of the epiphysis. The proliferative zone, the following layer toward the diaphysis, has stacks the slightly-larger chondrocytes. The continually makes brand-new chondrocytes via mitosis. The zone the maturation and also hypertrophy consists of chondrocytes that are older and also larger than those in the proliferative zone. The an ext mature cells are located closer to the diaphyseal end of the plate. In this zone, lipids, glycogen, and also alkaline phosphatase accumulate, bring about the cartilaginous matrix to calcify. The longitudinal development of bone is a result of cellular department in the proliferative zone in addition to the mature of cell in the zone the maturation and hypertrophy. The zone the calcified matrix, the zone closest come the diaphysis, has chondrocytes that are dead because the matrix around them has actually calcified. Capillaries and osteoblasts from the diaphysis pass through this zone. The osteoblasts secrete bone organization on the remaining calcified cartilage. Thus, the zone that calcified matrix connects the epiphyseal plate come the diaphysis. A bone grows in length when osseous organization is added to the diaphysis.

After the zone the calcified matrix, over there is the zone of ossification, i beg your pardon is actually part of the metaphysis. Arteries from the metaphysis branch through the newly-formed trabeculae in this zone. The newly-deposited bone organization at the optimal of the zone the ossification is dubbed the major spongiosa. The larger bone at the bottom the the zone of ossification is dubbed the an additional spongiosa.

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Figure \(\PageIndex1\): Longitudinal bone growth: The epiphyseal bowl is responsible because that longitudinal bone growth. This illustration mirrors the zones bordering the epiphyseal key of the epiphysis. The topmost great of the epiphysis is the to make reservation zone. The second zone, the proliferative zone, is whereby chondrocytes room continually experience mitosis. The next zone is the zone of maturation and hypertrophy whereby lipids, glycogen, and alkaline phosphatase accumulate, causing the cartilaginous matrix to calcify. The complying with zone is the calcified matrix whereby the chondrocytes have hardened and die as the matrix approximately them has actually calcified. The bottom-most heat is the zone the ossification which is part of the metaphysis. The newly-deposited bone tissue at the top of the zone the ossification is referred to as the primary spongiosa, while the older bone is labeling the second spongiosa.

Bones proceed to prosper in length until early adulthood with the price of growth controlled by hormones. As soon as the chondrocytes in the epiphyseal key cease your proliferation and bone replace instead replace the cartilage, longitudinal expansion stops. Every that remains of the epiphyseal bowl is the epiphyseal line.

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Figure \(\PageIndex1\): From epiphyseal plate to epiphyseal line: as a bone matures, the epiphyseal plate progresses come an epiphyseal line. (a) Epiphyseal plates are visible in a cultivation bone. (b) Epiphyseal lines room the remnants that epiphyseal bowl in a mature bone.