[Morphologic studies of the beginning of vascularization and ossification in human thyroid cartilage]

In contrast to the cartilaginous preformed bones of the skeleton, ossification of human thyroid cartilage begins at the end of the second decade of life. The process continues until an advanced age and shows sex differences. An in-growth of blood vessels by cartilage canals is a prerequisite for ossification. The aim of the study was to investigate the temporal and spatial appearance of cartilage canals in thyroid cartilage. Extracellular matrices of cells in cartilage canals were characterized immunohistochemically. Corrosion casts indicated that the cricothyroid branch of the superior thyroid artery was involved in vascularization of the thyroid cartilage. The first cartilage canals were detectable at the end of puberty, always lying at certain distances to almost ossified areas of the thyroid cartilage. The extracellular matrix localized at the border of the cartilage canals reacted with antibodies against type I collagen and type III procollagen, as well as with antibodies against type II collagen. This finding suggests that these cells are intermediate between fibroblasts and chondrocytes.