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Skeletal and Muscular Systems Skeletal System • • • • The framework for your body 206 bones “Os-” bone; “Osteo-” bone Osteocytes are bone cells Bone contains: • Minerals – especially calcium which provides for the hardness of bone • Collagen fibers which provides strength of bone Bone has an excellent blood supply Joint • “art-” and “arthr-” mean joint • Ligaments stabilize joints • Cartilage caps the bones at the joint for a smooth surface Cartilage • “chondr-” means cartilage • Healing capability is poorer than bone Skeleton Function • • • • • • Framework Support Movement Protection Blood cell production from bone marrow Storage of minerals & fat Disorders of Skeleton-Osteoporosis Incidence • Common in the U.S. • Responsible for many fractures each year Cause • • • • • • Inadequate calcium Females, older more commonly Sedentary lifestyle Poor diet Pregnancy giving calcium to fetus Menopause lead to calcium withdrawal from bone Prevention/Treatment • Weight-bearing exercise • Calcium in diet • Estrogen replacement therapy after menopause • Drugs, such as Fosamax Arthritis • Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the joints in the body leading to their gradual destruction Arthritis • Osteoarthritis is the wear and tear arthritis due to joint damage and injuries Sprain • Joint injury that stretches or tears supportive ligaments • A severe sprain can result in a dislocation Fracture • Generally bones heal well with proper alignment, stabilization, and without infection Fractures • • • • Hairline or greenstick Simple Compound = Open Comminuted Muscular System • “Myo-” means muscle • Muscle tissue is capable of contraction Smooth muscle • Found in the wall of tubular structures such as intestine • Involuntary • Smooth appearance microscopically • Peristalsis is a wave like contraction of smooth muscle Cardiac Muscle • Heart muscle • Involuntary • Striated, or striped when observed microscopically Skeletal Muscle • Muscle attached to the skeleton • Voluntary • Striated microscopically Skeletal Muscle • Tendons attach muscle to bone Microscopic Muscle • Myofiber = muscle cell • Myofibril = the striated parts of the muscle cell • Myofilaments = the proteins that make up the myofibrils Myofilaments • The two main proteins that comprise the myofilaments are: – Myosin – very thick protein – Actin – very thin protein Sarcomere • The actin and myosin in the muscle cells are arranged in small groups called SARCOMERES • Since contraction occurs at the microscopic level of the sarcomere, the sarcomere is the functional unit of contraction Sliding Filament Theory • This describes the mechanics of muscle contraction • The myosin “heads” grab on to the actin protein and pull the actin towards the center of the sarcomere, making the sarcomere shorter. 0018.exe ATP • ATP is necessary for muscle contraction • Running out of ATP leads to muscle fatigue Motor Neuron • Skeletal muscle will not contract unless a motor neuron (movement nerve cell) stimulates it to contract Motor Unit • A motor neuron plus how every many skeletal muscle cells it serves is a motor unit • A motor unit that has one neuron to one muscle cell allows for very precise movements • A motor unit that has one neuron to 400 muscle cells does not provide precise control