Endochondral ossification and long bone growth in humans
Endochondral ossification is the process in which the embryonic cartilaginous model of most bones, which supplies the longitudinal growth and is slowly replaced by bone. Endochondral ossification allows a growing bone to bare weight during its development. The endochondral process of ossification provides a framework for a more rigid skeletal material.
Long bones of the limbs and ribs develop by endochondral ossification. Characteristics of endochondral ossification include, the presence of a hyaline cartilage model of the bone and the presence of cartilage, along with the bone during the ossification process. Endochondral ossification occurs in the fetus, when the skeleton starts to
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A miniature model of the future bone develops in the fetus. A thin tubular bony collar forms around the middle of the cartilage model of the developing bone. This is an indication that endochondral ossification is about to start. Chondrocyte hypertrophy is in the centre of the cartilage model, chondrocytes increase in size and creates alkaline phosphatase, which is secreted into the extra- cellular matrix.
Matrix calcification is the calcification of the cartilage matrix occurs around the enlarged chondrocytes, the chondrocytes die because nutrients are unable to diffuse through the calcification matrix. The calcified matrix and moribund chondrocytes break down and lacunae become confluent. An enlarging cavity is produced in the cartilage model. Blood vessels penetrate the bony collar through channels on the spongy bone. The enlarging cavity in the middle of the cartilage model becomes vascularised and myeloid cells become established, forming the marrow cavity.
The cartilage model enlarges as the fetus grows. At both ends of the enlarging marrow cavity, cartilage goes through changes that are similar to the changes that take place earlier in the centre of the model. These changes (which include chondrocytes and matrix at both ends of the cartilage model) generate the growth plates (epiphyseal plates). A growth pate in the region of the developing long bone as long it is still