ABSTRACT
Bone is the hallmark of vertebrate tissues, but in embryonic development the primordial and dominant structure of the skeleton is cartilage. In the midsection of the shaft a bud of osteogenic cells, capillaries, and pericytes derived from the periosteum now penetrates the calcified cartilage at some site, usually near the middle of the model. Consistent with the high metabolic rate associated with the rapid cell proliferation and matrix synthesis, the growth plate is the cartilage in the body most extensively supplied by blood vessels. The large aggregating Proteoglycans (PG) is the major PG in cartilage, representing some 5 to 10% of the wet weight of the tissue. Biochemical studies of cartilage mineralization are difficult because of the limited possibilities of gaining access to the specific sites of interest. In this context, the substantial dynamics of the tissue should also be emphasized, a fact that makes firm conclusions on the line of events at the molecular level difficult.
