Does the periosteum produce the osteoblasts for compact bone formation, and the Endosteum for the spongy bone?
Both Periosteum and Endosteum are sources of fibroblasts which can differentiate into osteoblasts (osteogenic cells). However, there is no clear-cut rule about periosteum/endosteum and compact/spongy bone. During the first formation of a bone (either endochondral or intramembranous) osteoid forms then spongy bone trabeculae are formed (both peri- and endosteum are involved). Then compact bone is formed by remodeling the spongy bone (and osteoid). Again, both peri- and endosteum are involved. • See RR&K p. 176-177. Notice the labels for “periosteal bone” and “endochondral bone”… both begin as osteoid then trabeculae, etc. • The process of healing a break also illustrates that there is no “rule” that periosteum always forms compact bone. During healing, the injury stimulates the cells of the periosteum to proliferate. Fibroblasts from periosteum and endosteum invade the injury site and begin to form callus (osteoid). The callus at first resembles fibrous C.T. then is gradually ossified
