Question

Describe the 5 zones of a metaphysis and the major distinctions between them.

Answer 1

Ans. 1. zone of reserve cartilage: this is region is farthest from the marrow cavity which consit of hyaline cartilage which yet shows no sign of transforming into bone.

2. zone of cell proliferation: a little closer to the marrow cavity whwere chondrocytes multy and arrange there in to longitudina column.

3. zone of cell hypertrophy: chondrocytrs cease to divide and begin to enlarge as like in foetus.walls of matrix between the lacunae become very thick.

4. zone of calcification: Minerals are deposited in the matrix between the columns of lacunae and calcify the cartilage. These are not the permanent mineral deposits of bone, but only a temporary support for the cartilage that would otherwise soon be weakened by the breakdown of the enlarged lacunae.

5. zone of bone deposition: Within each column, the walls between the lacunae break down and the chondrocytes die. This converts each column into a longitudinal channel , which is immediately invaded by blood vessels and marrow from the marrow cavity. Osteoblasts line up along the walls of these channels and begin depositing concentric lamellae of matrix, while osteoclasts dissolve the temporarily calcified cartilage.