The skeletal system includes the osseous tissues of the body and the connective tissues that stabilize or interconnect the individual bones. The bone is a dynamic tissue. Throughout the lifespan, bone adjusts to the physiologic and mechanical demands placed on it by the processes of growth and remodeling. Bone serves the organism at multiple levels: As a system, bones permit the organism to locomote effectively and to maintain posture by bearing loads without deformation, by providing rigid attachment sites for muscles and acting as a system of levers to amplify small movements. As an organ, bones protect the viscera and house the hemopoietic tissue (red marrow). As a tissue, bones serve as a reservoir of readily mobilizable calcium, an ion vital for many metabolic processes including cell motility, excitability, secretion, phagocytosis, intermediary metabolism, respiration, and reproduction.
Bones (or osseous material) serve a number of diverse purposes in the human anatomy. In addition to providing structure, leverage, protection, and support for the organs of the body, bones also house marrow, which produces blood cells. Within the bones are also stored the calcium deposits which the body may access, via resorption, when needed. Additionally, bones detoxify the system, by removing heavy metals, such as lead and arsenic, as well as other toxins, from the bloodstream. The skeletal system provides structural support for the entire body. Individual bones or groups of bones provide a framework for the attachment of soft tissue and organs. Delicate tissues and organs are often surrounded by skeletal elements. The ribs protect the heart and lungs, the skull encloses the brain, the vertebrae shield the spinal cord, and the pelvis cradles delicate digestive and reproductive organs. Red blood cells and other blood elements are produced within the bone marrow that fills the internal cavities of many bones.