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Lengthening of long Bones

The epiphyseal plate is the area of development in a lengthy bone. It is a great of hyaline cartilage wherein ossification occurs in immature bones. Top top the epiphyseal side of the epiphyseal plate, cartilage is formed. On the diaphyseal side, cartilage is ossified, allowing the diaphysis to thrive in length. The metaphysis is the wide part of a lengthy bone in between the epiphysis and the small diaphysis. That is taken into consideration a part of the growth plate: the component 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 the cells and also activity.

The reserve zone, the an ar closest come the epiphyseal end of the plate, contains small chondrocytes within the matrix. These chondrocytes carry out not get involved in bone growth; instead, lock secure the epiphyseal plate to the osseous organization of the epiphysis. The proliferative zone, the following layer towards the diaphysis, consists of stacks of slightly-larger chondrocytes. That continually makes brand-new chondrocytes via mitosis. The zone of maturation and also hypertrophy includes chondrocytes that room older and larger than those in the proliferative zone. The an ext mature cells are situated closer come the diaphyseal end of the plate. In this zone, lipids, glycogen, and also alkaline phosphatase accumulate, leading to the cartilaginous matrix to calcify. The longitudinal development of bone is a an outcome of cellular department in the proliferative zone together with the tires of cell in the zone the maturation and hypertrophy. The zone of calcified matrix, the ar closest come the diaphysis, includes chondrocytes that room dead because the matrix around them has calcified. Capillaries and also osteoblasts from the diaphysis permeate this zone. The osteoblasts secrete bone tissue on the remaining calcified cartilage. Thus, the zone of calcified procession connects the epiphyseal plate come the diaphysis. A bone grow in length when osseous organization is added to the diaphysis.

After the zone of calcified matrix, there is the zone the ossification, which is actually part of the metaphysis. Arteries native the metaphysis branch with the newly-formed trabeculae in this zone. The newly-deposited bone organization at the height of the zone of ossification is dubbed the main spongiosa. The larger bone at the bottom the the zone that ossification is dubbed the an additional spongiosa.

Figure \(\PageIndex1\): Longitudinal bone growth: The epiphyseal key is responsible because that longitudinal bone growth. This illustration mirrors the area 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 are continually undergoing mitosis. The following zone is the zone of maturation and hypertrophy whereby lipids, glycogen, and alkaline phosphatase accumulate, bring about the cartilaginous matrix to calcify. The complying with zone is the calcified matrix wherein the chondrocytes have actually hardened and also die together the matrix about them has actually calcified. The bottom-most row is the zone that ossification i m sorry is component of the metaphysis. The newly-deposited bone tissue at the peak of the zone the ossification is referred to as the major spongiosa, when the older bone is labeling the second spongiosa.

Bones proceed to grow in length until early on adulthood through the rate of growth managed by hormones. When the chondrocytes in the epiphyseal plate cease your proliferation and also bone replace instead instead the cartilage, longitudinal growth stops. Every that stays of the epiphyseal key is the epiphyseal line.

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