Vascularization and cartilage mineralization of the thyroid cartilage of Munich minipigs and domestic pigs

Thyroid cartilages of Munich minipigs and domestic pigs were investigated b y polychrome sequential labeling, radiography, intravascular injections, hi stologic examination and scanning electron microscopy in order to gain furt her insight into the process of vascularization and cartilage mineralizatio n. The relationship between vascularization and cartilage mineralization ha s only been studied in chondroepiphyses of long bones. Vessels branch off t he perichondrial vascular network and enter parts of the thyroid cartilage with a large transverse diameter. Cartilage canals, which are perichondral invaginations, contain an arteriole, a venule, a capillary network and conn ective tissue. The capillaries form a glomerulus-like structure deep in the matrix of the cartilage. Neighbouring cartilage canals do not display any anastomoses. Cartilage mineralization occurs in large areas of the thyroid cartilage. It is only found in the interterritorial extracellular matrix. M ineralization of the cartilage is evident in areas supplied with cartilage canals as well as in non-supplied areas. Mineralized interterritorial matri x is composed of circular structures of different sizes fusing to form plaq ues. In scanning electron microscopy circular structures appear as globules . It is possible to visualize the dynamic process of cartilage mineralizati on with polychrome sequential labeling; it proceeds up to 4 mu m per week. Distribution of cartilage canals reveals their nutritional role for the car tilage. According to investigations in chondroepiphyses, cartilage minerali zation starts adjacent to the glomerular end of cartilage canals. In contra st, no correlation between cartilage vascularization and the beginning of c artilage mineralization of the thyroid cartilage of Munich minipigs and of domestic pigs has been found.