General Anatomy of the Locomotor System The skeleton, the supporting framework of the body, is formed by bony and cartilaginous elements, connected by connective tissue structures. Its parts are moved or held in defined positions or postures by the skeletal musculature. The overarching term locomotor system includes the skeleton and the musculature. The passive locomotor system consists of the skeleton and its joints (articulations), while the active motor system includes the striated muscles, the tendons, and their auxiliary structures (muscle fasciae, bursae, tendon sheaths, and sesamoid bones). Beside their supporting function, the skeletal elements and their joints serve to provide levers for the muscles during locomotion. The skeletal elements, joints, and skeletal musculature together form the organs of locomotion. In addition, the skeletal elements function to protect other organ systems (bones of the skull, vertebral canal, chest cage). The Bones The bony skeleton consists of bones of various structures and shapes. In the adult human, the skeleton is composed of about 200 individual bones, which are connected by cartilaginous, fibrous, and synovial joints. Each bone, with the exception of the cartilaginous joint surfaces and areas where flat tendons are attached, is enclosed in a connective tissue sheath, the periosteum, like a stocking. The shape of each bone is determined genetically, but its structure depends largely on the type and extent of the mechanical demands placed on it. According to their external shape, bones are divided into
