A. Structure - Your skeletal system is your basic framework in your body.

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1 II. Skeletal System A. Structure - Your skeletal system is your basic framework in your body bones - Comprise the adult human body. 2. "os-", "osteo-" Both of these roots mean bone. What is an osteocyte? Hint: Remember - cyt means cell. 3. Osteocytes - Bone is a connective tissue comprised of a group of cells called osteocytes. 4. Calcium & Phosphorus - Bone gets its hardness from minerals, especially calcium. 5. Collagen - Bone gets its strength from these protein rope-like fibers. 6. Excellent blood supply - This excellent blood supply gives the bone necessary nutrients for growth, repair and remodeling. In general, tissues with a good blood supply have good healing potential. 7. Joint - The junction between two different bones is termed a joint. a. "art-", "arthr-" - Both roots mean joint. Use your roots and define arthritis. b. Ligament - A ligament is a connective tissue band stabilizing a joint; holding the bones in place. Ligament healing is very slow, and not as complete as in bone itself. c. Cartilage - Cartilage caps the bones of most joints to provide a smooth surface for movement of the joint. Cartilage is a connective tissue & is found in the body in joints, in your nose, your trachea (windpipe) and your ears. 1. "chondr -" This root means cartilage. What is Chondritis? A chondrocyte? 2. Healing capability - Unfortunately, cartilage has an awful healing capability. It is avascular (this means without blood vessels). B. Function of skeletal system 1. Framework, Support 2. Movement, Transmission of force 3. Protection 4. Blood Cell Production from inside of the bones, termed the bone marrow 5. Storage of fat and minerals (especially calcium) C. Disorders of Skeleton 1. Osteoporosis

2 a. Incidence - Osteoporosis, which literally means porous bones, affects 15 million people in the U.S. per year. It is responsible for 1.2 million fractures per year. It is responsible for more than 200,000 hip fractures per year. It results in 1/3 of women in the U.S. to have a vertebral fracture by age 65, which can result in the characteristic hunchback hump, called Dowager's hump % of all victims of osteoporosis die of complications. b. Cause and risk factors Bones become weakened by inadequate calcium Sex (female more often), age (older), lifestyle (sedentary lifestyle increases risk), heredity (it runs in families), diet (lack of enough calcium in diet, frequent starvation diets), pregnancy (giving calcium to fetus at cost of depriving one's own body of calcium) Menopause - The lack of estrogen after menopause in women causes calcium to be pulled out of the bone at an increased rate of seven times normal. c. Prevention and Treatment Weight-bearing exercise, such as walking, keeps the bones strong. Calcium in the diet - Check with your doctor for your particular situation, but average amounts needed are 1000 mg/day for males and females before menopause, 1500 mg/day for females after menopause. Examples of calcium - rich foods are milk (one cup has about 300 mg calcium), cheese (one ounce of Swiss cheese has about 270 mg. calcium), broccoli (one medium stalk has about 200 mg calcium), yogurt (one cup of plain low fat yogurt has more than 400 mg calcium), and sardines (3 oz. unboned sardines have about 370 mg calcium). Of course many calcium supplements are available, but the calcium is not readily digested in many of the supplements. Check with your doctor before purchasing a calcium supplement. Estrogen replacement therapy after menopause Fosamax - An excellent drug for helping a person increase their bone density. Side effects include ulcers (esophagus, stomach). 2. Arthritis - Joint inflammation. a. Rheumatoid arthritis - This is an autoimmune disease which means that the immune system gets "mixed up" and thinks that components of your joints are foreign and attacks them. This leads to gradual destruction of the joints. Treatment includes pain killers and corticosteroids. Corticosteroids (e.g. Prednisone, Cortisone) are anti-inflammatory and suppress the immune response. b. Osteoarthritis - This is the wear and tear type of arthritis. It is typically caused by injury to the joint or overusing a joint with repetitive motions over a period of years. As sharp spicules of bone form, pain occurs upon bending the joint. Sometimes the arthritis becomes so severe that the joint ends up fused.

3 3. Sprain - A sprain is a joint injury, such that the joint is twisted or overextended resulting in stretching or even tearing of the supportive ligaments. If the sprain is severe enough, it results in loss of alignment of the bones which is a dislocation. 4. Fracture - In general, bone fractures heal very well - provided that the bones are in alignment and no infection occurs. Healing time varies with the type and severity of the fracture, but an average would be 8 weeks for an adult and 4 weeks for a child (due to the rapid cell growth rate in children). a. Hairline or Greenstick Fracture - A tiny crack in the bone, may go unnoticed. Healing capability is excellent, provided that the fracture does not extend into the joint. (Remember that cartilage does not heal well.) b. Simple Fracture- The bone is completely broken into two pieces. If stabilized, the healing capability is quite good. c. Compound = Open Fracture - With this fracture, the broken end(s) of the bone protrudes through the skin. An added complication of this type of fracture is infection. d. Comminuted Fracture - The bone is broken into more than two pieces. A shattered bone is an example. Often this type of fracture has the worst prognosis, as the small pieces of chipped bone can become detached from their blood supply and die. IV. Muscular System A. Structure ("myo-" means muscle) - Muscle tissue is capable of contraction. There are three types of muscle tissue: 1. Smooth muscle a. Location - Found in the wall of tubular structures; e.g. wall of intestine or blood vessel. b. Involuntary - You cannot voluntarily control these muscles. c. Smooth - The name of this muscle comes from the fact that it looks smooth when viewing it microscopically. d. Peristalsis - This muscle can do peristalsis, which is a wave like contraction. For example, peristalsis moves your partially digested food along your intestine. 2. Cardiac muscle a. Location - Wall of the heart.

4 b. Involuntary - It is responsible for pumping your blood and you cannot voluntarily control this muscle. c. Striated - When viewed microscopically, it appears striated, or striped. 3. Skeletal muscle a. Location - This muscle is attached to your skeleton to allow you to move your skeleton and have posture. b. Voluntary - Although reflex responses are possible, you CAN voluntarily control this muscle. You can send a message to your Biceps and "tell it" to bend your elbow when you want. c. Striated - It is also striped microscopically. B. Contraction of Skeletal Muscle 1. Tendon - If skeletal muscle moves the skeleton, it must have an attachment to bone. That is what the tendon does - attaches muscle to bone. 2. Myofiber = Muscle cell - You can contract a few to all of the myofibers in a given muscle to allow the range of muscle tone to maximum movement. Refer to an illustration in your book of a myofiber and its components as your read this section. 3. Myofibril - Striped or striated cylinders found inside of a myofiber are myofibrils. 4. Myofilaments - The myofibrils are made of proteins that are responsible for contraction. Although muscle cells cannot go through mitosis to make more muscle cells to make you stronger, each muscle cell CAN add more of the contractile myofilaments to make each CELL stronger. This is what happens after weight lifting and the muscle cells enlarge. Two main myofilaments slide along each other to result in contraction. a. Myosin - This myofilament is very thick and can "grab" the actin and squeeze it together, resulting in cell shortening or contraction. b. Actin -This myofilament is very thin and anchors to the ends of the contractile unit, or the sarcomere. c. Sarcomere - The sarcomere is a set of myosin and actin. It is the functional unit of muscle contraction, because it is the sarcomere that shortens during contraction. 5. Sliding Filament Theory - This theory describes the mechanics of muscle contraction. The myosin has "heads" sticking out that grab on to the actin and pull it towards the center of the sarcomere, thus shortening the sarcomere.

5 6. ATP - ATP must be present for muscle contraction. If you run out of ATP, your muscles cannot work, and you have muscle fatigue. 7. Motor neuron - Skeletal muscle will not contract, unless a nerve cell, termed a motor neuron tells it to contract. That is why this muscle can be voluntarily controlled. Your muscle will be paralyzed if the neuron is injured (as in spinal cord injuries) even if there is nothing wrong with the muscle at all. The term Motor Unit means the motor neuron plus how ever many muscle cells it serves. If the Motor Unit is one neuron with a thousand muscle cells, all of those muscle cells will do the same thing at the same time and you do NOT have very precise control over that movement. An example would be your lower back muscles. If the Motor Unit is one neuron and one muscle cell, you would have very precise control over that area, controlling each cell independently. Examples are your eye movement muscles.