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Lengthening of Long Bones

The epiphyseal plate is the area of growth in a long bone. It is a layer of hyaline cartilage where ossification occurs in immature bones. On the epiphyseal side 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 long bone between the epiphysis and the narrowhead diaphysis. It is taken into consideration a part of the development plate: the component of the bone that grows during childhood, which, as it grows, ossifies near the diaphysis and the epiphyses.

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The epiphyseal plate is written of 4 areas of cells and also activity.

The reserve zone, the area closest to the epiphyseal finish of the plate, contains tiny chondrocytes within the matrix. These chondrocytes perform not take part in bone growth; instead, they secure the epiphyseal plate to the osseous tproblem of the epiphysis. The proliferative zone, the next layer toward the diaphysis, contains stacks of slightly-bigger chondrocytes. It continually makes new chondrocytes through mitosis. The zone of maturation and also hypertrophy has chondrocytes that are older and also bigger than those in the proliferative zone. The even more mature cells are positioned closer to the diaphyseal finish of the plate. In this zone, lipids, glycogen, and alkaline phosphatase accumulate, resulting in the cartilaginous matrix to calcify. The longitudinal growth of bone is a result of cellular department in the proliferative zone together with the maturation of cells in the zone of maturation and also hypertrophy. The zone of calcified matrix, the zone closest to the diaphysis, has chondrocytes that are dead bereason the matrix around them has calcified. Capillaries and also osteoblasts from the diaphysis penetrate this zone. The osteoblasts secrete bone tworry on the remaining calcified cartilage. Hence, the zamong calcified matrix connects the epiphyseal plate to the diaphysis. A bone grows in length when osseous tissue is added to the diaphysis.

After the zone of calcified matrix, tbelow is the zone of ossification, which is actually part of the metaphysis. Arteries from the metaphysis branch through the newly-developed trabeculae in this zone. The newly-deposited bone tconcern at the peak of the zone of ossification is referred to as the major spongiosa. The older bone at the bottom of the zamong ossification is dubbed the second spongiosa.

Figure (PageIndex1): Longitudinal bone growth: The epiphyseal plate is responsible for longitudinal bone expansion. This illustration reflects the zones bordering the epiphyseal plate of the epiphysis. The topmany layer of the epiphysis is the reserve zone. The second zone, the proliferative zone, is wright here chondrocytes are continually undergoing mitosis. The next zone is the zone of maturation and hypertrophy wright here lipids, glycogen, and alkaline phosphatase accumulate, resulting in the cartilaginous matrix to calcify. The adhering to zone is the calcified matrix wright here the chondrocytes have actually hardened and die as the matrix about them has calcified. The bottom-most row is the zamong ossification which is component of the metaphysis. The newly-deposited bone tissue at the peak of the zone of ossification is called the primary spongiosa, while the older bone is labeled the secondary spongiosa.

Bones proceed to grow in size until early on adulthood through the rate of expansion controlled by hormones. When the chondrocytes in the epiphyseal plate cease their proliferation and also bone relocations the cartilage, longitudinal growth stops. All that stays of the epiphyseal plate is the epiphyseal line.

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Figure (PageIndex1): From epiphyseal plate to epiphyseal line: As a bone matures, the epiphyseal plate progresses to an epiphyseal line. (a) Epiphyseal plates are visible in a growing bone. (b) Epiphyseal lines are the remnants of epiphyseal plates in a mature bone.