Fig. 2

Scanning electron microscopy of the articular cartilage in 1-day (A1–4), 5-day (B1–4) and 10-day (C1–4) postnatal rats. A1, B1, C1 parenchyma of the articular cartilage (AC) in each group. A2 the chondrocytes densely reside in the AC. A3, extracted from the red box in A2 typical face-to-face structure of the chondrocytes. (A4, extracted from the blue box in A2) The chondrocytes are in fine activity with complete cellular structure and abundant cell processes. (B2, extracted from the red box in B1) the cartilage canal (red box). (B3, extracted from the red box in B2) vascular wall and erythrocytes in the cartilage canal. (B4) The chondrocytes are in poor activity with few cell processes. (C2, extracted from the red box in C1) The secondary ossification center is connected with cartilage canals. (C3, extracted from the red box in C2) The cartilage canal is surrounded by abundant chondrocytes. C4 the chondrocytes and rough surface of the matrix with much calcium deposition