The human body has five types of bones:

• Long bones are consisting of a long shaft (the diaphysis) plus two articular (joint) surfaces, called epiphyses. They are comprised mostly of compact bone, but are generally thick enough to contain considerable spongy bone and marrow in the hollow centre (the medullary cavity). Most bones of the limbs (including the three bones of the fingers) are long bones, except for the kneecap (patella), and the carpal, metacarpal, tarsal and metatarsal bones of the wrist and ankle.
• Short bones are roughly cube-shaped, and have only a thin layer of compact bone surrounding a spongy interior. The bones of the wrist and ankle are short bones, as are the sesamoid bones.
• Flat bones are thin and generally curved, with two parallel layers of compact bones sandwiching a layer of spongy bone. Most of the bones of the skull are flat bones, as is the sternum.
• Irregular bones do not fit into the above categories. They consist of thin layers of compact bone surrounding a spongy interior. As implied by the name, their shapes are irregular and complicated. The bones of the spine and hips are irregular bones.
• Sesamoid bones are bones embedded in tendons. Since they act to hold the tendon further away from the joint, the angle of the tendon is increased and thus the force of the muscle is increased. Patella is the example of sesamoid bone.