The document discusses the structure and function of bones and the skeleton. It describes how bones provide rigid support for the body and act as levers for muscles. The skeleton is made up of an axial skeleton including the skull, spine and rib cage, and appendicular skeleton of the upper and lower extremities. Bones are designed to withstand mechanical strains from movement, gravity and supporting weight. Their internal structure of compact and spongy bone along with marrow allows bones to be strong but also light enough for movement. Proper skeletal alignment and dynamic movement are important for building strong bones and maintaining health.