Skeletal System Bone Formation * Ossification- the process by which bone is formed * ossification of embryonic fibrous tissue frame begins around the sixth or seventh week of life and continues throughout adulthood. Two methods of bone formation * intramembranous ossification- the formation of bone directly on or within fibrous connective tissue membranes. * produces the flat bones of the skull and most of the clavicle (collarbone) * endochondral ossification- the formation of bone within a cartilage model. The two methods do not lead to different structure of bone. Both methods involve the replacement of a preexisting connective tissue with bone. Bone Formation (cont.) Intramembranous Ossification flat bones of the skull, mandible (lower jaw bone), and the clavicles (collar bone). * at the site where bone is to be developed, cells in the mesenchyme began to differentiate into osteoprogenitor cells and then to osteoblasts. The osteoblast secrete the bony matrix (osteoid-soft collagenous tissue void of minerals) until it completely surrounds them. This primary site of bone development is called the
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