Endochondral ossification

At the top of the image in the zone of proliferation (yellow arrow), chondrocytes in hyaline cartilage are dividing to form linear isogenous groups of cells (black arrows). Linear proliferation maintains the thickness of the epiphyseal plate while growth in length is occurring.

Between the lines, chondrocytes are maturing and increasing in size (hypertrophying). During this process, the cells secrete alkaline phosphatase, creating an environment conducive to calcification of the cartilage matrix. A calcified matrix prohibits nutrients from reaching the chondrocytes, and the cells die. This sequence of regressive changes forms the zone of maturation-hypertrophy-calcification.