BONES

The classification of bones is based on three principles: the shape and structure of a bone, its development and function (Figs. 33-34). Bones are divided into long (tubular), short (spongy), irregular (mixed) and pneumatic (Fig. 32).

Fig. 32. The bones of different shape: 1 - pneumatized bone (ethmoid bone); 2 - long (tubular) bone; 3 - flat bone; 4 - spongy (short) bones; 5 - irregular bone