Fig. 3

Transmission 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 chondrocytes and surrounding matrix in the articular cartilage (AC). (A2–4, extracted from the red boxes in each upper image) the nerve fiber around the chondrocyte, with typical lamellar structure of myelin sheaths consisting of 6–7 layers, and the contact between it and the chondrocyte. (B2–4, extracted from the red boxes in each upper image) a nerve fiber near a chondrocyte. The distance between nerve fibers and the cell processes of chondrocytes increased, and the medullary sheath has less layers (4–5) and looser structure. C2 nerve fibers away from the chondrocytes. (C3 extracted from the red boxes in C2, and C4 from other area) even less layers (2–3) and looser structure of the myelin sheaths and signs of degradation of the nerve fibers