Morphometric study of cartilage dynamics in the chick embryo tibia. I. Methodology and tissue compartments in normal embryos.

Cartilage dynamics during the development of the chick embryo tibia has been studied by means of morphometric methods, from the 11th to the 14th days. The volume densities of the structures enclosed by the perichondrium-periosteum did not change significantly through the age span studied, whereas the absolute volumes of these structures increased during the whole period under investigation. The cartilage volume showed the most rapid increase from Day 12 to Day 13 (by a factor of x1.74). The volume of the invading connective and vascular tissue increased rapidly from Day 11 to Day 14. The rate of cartilage formation decreased from 7.60 +/- 1.02 to 3.82 +/- 0.89 mm3/day (from Day 13 to Day 14), whereas the rate of cartilage resorption increased until Day 13 (by a factor of x2.71), reaching a plateau after this age. Although cartilage formation was higher than resorption during this period, the changes found by Day 13 indicate that shortly after this age cartilage resorption will predominate over cartilage formation, leading to the disappearance of the cartilaginous model.