in/jae/t02/i2/jaet02i2p 199.pdfExplanation:The clavicle is the first bone to begin the process of ossification (laying down of minerals onto a preformed matrix) during development of the embryo, during the fifth and sixth weeks of gestation. However, it is one of the last bones to finish ossification at about 21-25 years of age.Its lateral end is formed by intramembranous ossification while medially it is formed by endochondral ossification.It consists of a mass of cancellous bone surrounded by a compact bone shell.The cancellous bone forms via two ossification centres, one medial and one lateral, which fuse later on.The compact forms as the layer of fascia covering the bone stimulates the ossification of adjacent tissue. The resulting compact bone is known as a periosteal collar.Even though it is classified as a long bone, the clavicle has no medullary (bone marrow) cavity like other long bones.It is made up of spongy (trabecular) bone with a shell of compact bone.">