The mandibular angular cartilage in the rat.

Histomorphological and histochemical aspects of the mandibular angular cartilage and its surrounding perichondrium are described from a material consisting of 46 rats aged between 1 and 56 days. Comparisons at 11-13 days with mandibular condylar cartilage reveal a marked concordance in their general composition. However, certain differences in extent of the subzones constituting the cartilage are present. These differences are suggested to express differences in growth rates between the structures. The study of the age changes which take place in the mandibular angular cartilage reveals an age-related change in direction of the muscles attached to the medially and laterally facing surfaces of the structure in combination with a change in direction of the connective tissue covering its posterior part. Such changes might be indications of changes in direction of the tensional forces acting on the cartilage. Ultimately, they might be related to the limited temporal maintenance of the structure.