The study of the bones that make up the skeleton, or framework of the body, is oste­ology.

The skeleton gives a basis for the external structure and appearance of most vertebrate animals as we know them (Figs. 4-1 and 4-2). All mammals share a basic body plan with striking similarities in skeletal structure. Differ­ences reflect adaptations to specific lifestyles.

The skeleton of a living animal is made up of bones that are themselves living structures. They have blood vessels, lymphatic vessels, and nerves; they are subject to disease; they can undergo repair; and they adjust to changes in stress. The functions of bones include provid­ing protection, giving rigidity and form to the body, acting as levers, storing minerals, and forming the cellular elements of blood.