Ultrastructure of the Bovine Synovial Membrane in Ontogenesis

Horky, D.: Ultrastructure of the Bovine Synovial Membrane in Ontogenesis. Acta vet. Bmo, 53, 1984: 107-117. Ultrastructural studies of the synovial membrane have been made on tissue samples obtained from 3 bovine adult individuals aged 3 to 5 years and 4 individuals aged 246 to 271 days after fertilization. The material was collected partly from the carpal, partly from hip joint for both light and electron microscopic histology. The synovial membrane is composed of specifically modified cells which can be differentiated in A and B type and of the intracellular substance on the basis of study of their submicroscopic structure. Subsynovial tissue is placed under the main synovial membrane. In synovial membrane of adult individuals A-cells form a nearly continuous cover and in between them there are B-cells deposited in clusters. Numerous secretory granules are placed in their cytoplasm and in the projections there are bundles of cytoplasmic filaments. Connections of desmosome type are not formed between the cells and basal membrane is missing, too. Intercellular areas are filled with amorphous ground substance with a prevailing amount of aperiodic fibrils. Synovial membrane has a similar arrangement during the fetal period. There are numerous B-cells which do not form clusters. The amount of organellae taking part on proteosynthesis in comparison with adult individuals is larger, giving evidence of their activity. Collagen fibrils were identified in these cells intracytoplasmatically as well as pervading through the cell membrane. On the surface of an adult as well as fetal synovial membrane we observed regions uncovered by cells, so that the intercellular substance is in a direct contact with the joint cavity. Synovial membrane, synovialocytes A, B, synovial matrix, synovial membrane surface. Structure and function of the synovial membrane has been studied since long. The first reports have been published in the year 1743 (Hunter see Stone 1947). Many authors were engaged in the microscopic structure of synovial membrane and described its function under normal and experimental conditions as well as pathological changes in animal and human material (see Jaffe 1972). First electron microscopic studies on the synovial membrane of calf, dog and guinea-pig published Langer and Huth (1960); synovial membrane of a rabbit described Ghadially and Roy (1966), later Krey et al. (1976), Oryschak and Ghadially (1976); comparison of the synovial membrane ultrastructure in man, mice, rat, rabbit and guinea-pig described Linck and Porte (1978), a proof on the secretory function of synovial membrane cells worked out Okada et al. (1981) who demonstrated secretory granules in the B synovialocytes of mice, rat, guinea-pig, rabbit and of man. Differences in composition and synovial membrane ultrastructure by rat and man described Roy and Ghadially (1967) and in the first place Wassilev (1972,1973,1975). Cutlip and Cheville (1973) presented a fundamental description on sheep. Langer and Huth (1960) have been the first who observed synovial membrane submicroscopic structure in calf and lately Howlett (1974) who described differences in ultrastructure of this tissue in bulls under pathological conditions.