The 206 bones that compose the adult skeleton are divided into five categories based on their shapes (Figure 6.6). Their shapes and their functions are related such that each categorical shape of bone has a distinct function.
Figure 6.6. Classifications of Bones
Bones are classified according to their shape.
A sesamoid bone is a small, round bone that, as the name suggests, is shaped like a sesame seed. These bones form in tendons (the sheaths of tissue that connect bones to muscles) where a great deal of pressure is generated in a joint. The sesamoid bones protect tendons by helping them overcome compressive forces. Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees. The patellae (singular = patella) are the only sesamoid bones found in common with every person. Table 6.1 reviews bone classifications with their associated features, functions, and examples.