medical freak: BONE CLASSIFICATION

Bones are classified according to appearance: long, short, flat and mixed. Bones entirely different in structure , function and origin form a single group . The group of flat bones, for instance, includes both the parietal bone, a typical membrane bone, which undergoes intramembranous ossification and the shoulder blade which is concerned with the functions of support and movement, ossified from cartilage and formed of ordinary spongy substance. A pathological process in the phalanges also differs in its course from that in the carpal bones, although both types of bones are referred to as short bones; the same applies to the thigh bone and rib included in the group of long bones.

It is therefore more proper to classify bones according to the three principles on which any anatomical classification should be based, i.e. form (structure), function and development. The following classification of bones can be suggested according to M.G. Prives:

I. Tubular Bones: These are composed of spongy and compact substance forming a tube with a marrow cavity; they perform all three functions of the skeleton(support,protection and movement).

a) Long Tubular Bones(arm bone, forearm bones, thigh bone and leg bones)

b)Short Tubular Bones(metacarpal, metatarsal, phalanges)

II. Spongy Bones: they consist mainly of spongy substance covered with a thin layer of compact substance.

a)Long Spongy Bones(ribs and sternum)

b)Short Spongy Bones(vertebrae, carpal, tarsal)

c)Sesamoid bones i.e. bones which resemble sesame seeds in shape, hence their name(the knee cap or patella, the pisiform bone)

III. Flat Bones

a)Flat Bones of the skull(frontal and parietal): They perform a function that is mainly protective.Their structure is dipole and they ossify from connective tissue.

b)Flat Bones of the girdles(shoulder blades, pelvic bones): Perform supportive and protective functions. Their structure is primarily spongy substance.