Question

Art-Ranking Activity: The process of endochondral ossification

Answer 1

The endochondral ossification is a process by which through a series of steps cartilage is gradually replaced by bone formation. This process starts from fetal development and continue through childhood where the cartilage is replaced and forms the bones as there is growth and development. Hence it starts with formation of cartilage and gradually it is replaced by bone. This process is majorly divided into multiple steps. Here are the steps and process of endochondral ossification.

i) During the first step, as the size of the cartilage becomes bigger, it increases the size of the chondrocytes which is located near the center of the shaft. This process starts with formation of cluster of chondrocytes and these cells proliferate and become bigger in size. As the cell start to grow, it weakens the cartilage. It tends to calcify the matrix and hardens the hyaline cartilage. This is followed by formation of bone collar around the hyaline cartilage.

ii) Next step is cavitation, and this is formed due to the death of the chondrocytes as they are not permeable to nutrient diffusion. The chondrocytes due to their inability to get nutrients die and form small cavity. Due to the formation of these cavities, it enables the blood vessels to travel through it.

iii) Next step is the periosteal bud development which helps in driving and supplying nutrients to the bone. The periosteal region forms a bud that contains blood vessel and nerves, and this helps in supplying nutrients through blood flow. This also helps in entry of cells like osteoblast and osteoclast which forms the spongy bone as the osteoblasts produce osteoid within the hyaline cartilage.

iv) This is followed by formation of medullary cavity and it continues the ossification. The elongation of the diaphysis region forms the medullary cavity and this is supported by the primary ossification center.

v) This is followed by elongation of epiphyseal region and forms the secondary ossification center. After it is completed, hyaline cartilage remains only on the ends of epiphyseal plates and all the rest is replaced by bone.