Eight small bones, the carpals, comprise the wrist. Five metacarpals form the palm of the hand, and the finger bones are made up of 14 phalanges in each hand. This girdle and the last two bones of the spine, the sacrum and the coccyx, form the pelvis. This part of the skeleton encircles and protects the internal organs of the genitourinary system. In each side of the pelvis is a socket into which a femur fits.
Leg bones are similar in construction to arm bones, but are heavier and stronger.
The thigh bone, or femur, which is the longest bone in the body, extends from the pelvis to the knee, and the tibia and fibula go from knee to ankle. The kneecap is a single bone, the patella. The way these bones are joined determines whether they can move and how they move. The elbow, for example, is a hinge joint, which allows bending in only one direction. Many joints, such as most of those in the skull, are rigid and permit no movement whatsoever.