intramembranous bone

Bone tissue forms directly within mesenchyme, and does not replace other tissues[TAO]. Intramembranous ossification is the formation of bone in which osteoblasts secrete a collagen-proteoglycan matrix that binds calcium salts and becomes calcified[GO]. Intramembranous ossification is the way flat bones and the shell of a turtle are formed[GO]. Unlike endochondral ossification, cartilage is not present during intramembranous ossification[WP].