Skeletal System it consist of three main types of tissues; muscles bones cartilage Functions of the skeletal system protection Support Muscle attachment movement storage of calcium blood cells formation Main types of skeletal system; exoskeleton in insects its functions include support, attachment of muscle for movement, protection and prevent water loss endoskeletons in vertebrates(eg humans) its functions include support, protection and movement Skeleton of Humans it is divided into three parts: Axial skeleton-skull, back bone and ribs Appendicular skeleton-limbs Girdles-hip and shoulder girder Bones Pectoral girdle- shoulder CONSIST OF; Shoulder a triangular, flat bone witha shallow cavity on narrower end. It joins the arm tto the axial skeleton. The collar bone it prevents the shoulder from bending inward. Arm - upper and lower arm Ulna and radius ulna is longer and thicker than radius has cavity where part of humorous fitted to make a hinge joint ulna has an extended bone Humorous A long bone with a rounded head-epiphysis and a long central shaft-endophysis Shallow cavity lose attachment oof the shoulder bone with the back side of ribs Joints Is a connection between two or more joints. They provide articulation between bones making movement possible. Types of joints Gliding joint e.g joints which occur between the vertebrate wrists and ankles the ends of the bones that make the joint are covered with cartilage they are held together by tough ligaments Synovial joint it is enclosed by fibrous capsule lined by synovial membrane which secretes synovial fluid into the synovial cavity the synovial fluid lubricates the joint they include hinge and ball and socket joints Hinge joint eg knee joint it allows movement in one plane, ball and socket joint eg hip joint; it allows rotation in all directions ELBOW Role of muscles in movement of human arm Muscles that bring about movement are antagonistic i.e when one set contracts the other relaxes Movement of the hinge joint of an arm moving arm upwards(biceps flexor) muscle contract whilst triceps muscle relax straightening the arm, biceps muscle relaxes whilst the triceps(extensor) muscle contract Antagonistic muscle of human forelimb the biceps muscles of the forelimb act as flexors while the triceps muscle act as extensors the biceps has its points of origin on the scapula and the point of insertion on the radius the triceps has its point of origin on the scapula and humorous and is inserted on the ulna when the muscles contract, the limb act as a lever with the pivot at the joint contraction of biceps muscles bends the arms while contractions of triceps extend the arm