Fine structure of the nucleus of ossification in cartilage

Abstract

Fine structure with endochondral ossification of the calcifying cartilage and bone matrix in the nucleus of ossification were investigated by a scanning electron microscope, using fracture surfaces of the nucleus in the cartilagious sternum of the fetus.
The chondrocyte lacunar wall in the superficial layer of the nucleus of ossification was formed by numerous calcospherites, and its surface was rough. The longitudinal septa of the hypertrophic layer was strand-shaped and calcified. The calcifying cartilage matrix in the part of the center of the trabeculae of the layer of ossification was mostly formed by dense calcified matrix. The gap of the calcospherites was formed by collagen fibrils. The calcifying cartilage matrix of the layer of ossification was highly calcified. There were many osteocyte lacunae showing irregularly arranged in the bone matrix of the fracture surface. The osteocyte lacunar wall was formed with dense networks of collagen fibrils.