How do bones form?
The process by which bones form, beginning in the eighth week of an embryo’s development, is known as osteogenesis or ossification. The majority of the skull bones and the clavicle develop through intramembranous ossification, in which the bones form directly from an embryonic tissue known as mesenchyme. All other bones of the body develop through endochrondral ossification, in which the bones are first formed in hyaline cartilage which then is gradually replaced by bone tissue. Endochrondral ossification of long bones begins in the diaphysis, or shaft, of the bone; the last stage is the ossification of the epiphyses, or the ends. This last stage occurs around the time of birth. Ossification continues throughout life, with the epiphyses finally fusing to the diaphysis in adulthood. Until then, a section of hyaline cartilage known as the epiphyseal plate remains between the diaphysis and the epiphysis.
