FELINE ARTICULAR-CARTILAGE IN THE PRENATAL AND EARLY POSTNATAL PERIODS - A SCANNING ELECTRON-MICROSCOPIC STUDY

The structure of articular cartilage from the femoral head was studied in the domestic cat by scanning electron microscopy. Tissue samples were collected from foetuses at 30, 40 and 48 days after fertilization and from young animals at 4, 8 and 43 days after birth. At 30 and 40 days after fertilization, the cartilage surface showed numerous elevations accumulated closely to each other. A fracture plane running through the cartilage collected at 40 days revealed chondrocytes situated in three layers. At 48 days the surface chondrocytes began to aggregate into groups of 4 to 6 cells and, amongst the groups, smooth areas appeared. Tbe entire surface was covered by a chondrosynovial membrane. The appearance of articular cartilage remained without noticeable changes after birth. At 4 days there were still groups of elevations seen in the previous period but they consisted of only 2 to 4 cells. These were often arranged in pairs with a shallow groove on the surface. The smooth areas increased in size. At 8 days some of the chondrocytes were encircled with a vallum and furrow. At 43 days the surface differed in appearance in different regions. There were still regions similar in structure to those at 8 days but the majority of the surface was restructured. The number of surface chondrocytes with the vallum and furrow had been reduced while the smooth regions had extended. The surface cartilage had attained the appearance of a young adult cartilage.