The Ultrastructural Interface of Bone Crystals and Organic Matrix in Woven and Lamellar Endochondral Bone

Abstract

Endochondral bone consists of three calcified regions: calcified cartilage, woven bone, and lamellar bone. Woven or immature bone begins when osteoblastic extrusions or buds calcify; from initial calcification loci, bone crystals grow radially to form spheroidal bone nodules. Nodules eventually coalesce into bone seams. Lamellar bone develops as a sequel to the calcification of cartilage or woven bone. Hydroxyapatite grows into lamellar bone and then is oriented parallel to collagen. Except for the stage of cartilage calcification, intramembranous and endochondral osteogenesis are similar.