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Skeletal and Muscular Systems Powerpoint #2 Unit 8 – Chapters 36 Working together to create movement Skeletal System Structures: Bones Cartilage Ligaments Functions Supports body Protects internal organs Allows for movement Stores mineral reserves Provides a site for blood cell formation • How many bones in a human Skeleton? • 206 • How many in babies? • ~ 300 • Axial Skeleton: spine, ribcage, skull • Appendicular: arms, legs, pelvic girdle, shoulders • What are bones? • A solid network of living cells and protein fibers that are surrounded by deposits of calcium salts Bones: 3 Parts Spongy bone • Not soft or spongy • Very strong • Structure resembles the supporting structure of bridges. • Strong but lightweight Compact bone: • Very dense (no spaces like spongy bone) • Outer portion of bone • Contains Haversian canal for veins and arteries to run through Haversian Canals Bone Marrow: • Soft tissue • Found in bone cavities • Yellow Marrow: fat cells • Red marrow: • makes red blood cells, platelets and most white blood cells • ~1/2 red marrow turns into yellow in adults • If severe blood loss, some yellow can turn back to red Development of bone: • Cartilage: Tough, elastic, connective tissue • Found in: ears, between bones, larynx, and other various places. Development of Bone • http://www.youtube.com/watch?v=78RBpWSOl08 • Ossification: cartilage replaced by bone • Osteoblasts:cells that build bone • Osteoclasts:cells that break down bone • Growth Plates (epiphyseal plates): found in most long bones (leg and arm bones) cartilage continues to grow here until completely replaced by bone during adolescence=stop growing Types of Joints -Ball and socket Types of Joints- Hinge Types of Joints- Saddle Types of Joints • Pivot Structure of Joints • Ligaments: Connects Bone to Bone • Tough, fibrous tissue Anterior Cruciate Ligament Fractures Structure of Joints • Bursa: small fluid-filled sac • provides a cushion between bones and tendons and/or muscles around a joint. Bursitis Arthritis Arthritis Rheumatoid arthritis Osteoarthritis Compare Osteoarthritis and normal knee Total Knee Replacement Total Knee Replacements Total Knee Replacement Osteoporosis 29 Types of Muscle The human body is comprised of ~640-850 muscles (sources varying regarding what is defined as different parts of a single muscle or as several muscles) makes up 30-35% (in women) and 42-47% (in men) of body mass. Three types of muscle: Skeletal muscle Cardiac muscle Smooth muscle 32 A. Skeletal (Striated) Muscle moves various parts of the skeleton voluntary control Repeated activation of a skeletal muscle can lead to fatigue Can have many nuclei Striated (striped appearance) 33 Skeletal Muscles work in PAIRS Bending or straightening of elbow requires the coordinated interplay of the biceps and triceps muscles 34 B. Smooth Muscle Located in the blood vessels, the respiratory tract, the iris of the eye, the gastro-intestinal tract contractions are slow and uniform Is fatigue resistant Activation is involuntary Has one nucleus 35 C. Cardiac Muscle Functions to provide the contractile activity of the heart Activation is involuntary (like smooth muscle) Can have 2 nuclei, usually has 1 Is very fatigue resistant 36 Components of skeletal muscle myofibril 37 muscle fiber muscle fiber bundle Muscle Fibers: Cylinder-shaped cells that make up skeletal muscle Made of myofibrils which is made up of a number of myofilaments Two types of protein myofilaments: - Actin: thin filament - Myosin: thick filament Divided into functional units called sarcomeres, seperated by region called Z lines. Group of fibers activated via same nerve: motor unit 38 High microscope magnification of sarcomeres within a myofibril 39 Muscle Contraction Muscle Contraction Steps 1. Myosin head attaches to binding site on actin forming a cross bridge 1. After the cross bridge is formed the myosin head bends, called a power stroke, pulling on the actin filaments and causing them to slide. 1. Myosin attached to actin until another ATP binds causing it to release (explains rigor mortis) 1. Muscle contraction is a little like climbing a rope. The cross bridge cycle is: grab -> pull -> release, repeated over and over Control of Muscle Contraction (animation) 1. 2. 3. 4. 5. Muscle cells are "shocked” by nerve impulses from motor neurons. Neurotransmitters (acetylcholine) are released by neuron, stimulating muscle fiber to release Ca2+ When a muscle is relaxed, tropomyosin blocks cross-bridges. When Ca2+ high enough, it binds to troponin, displacing tropomyosin, exposing myosin binding sites on actin. Myosin can now form crossbridge Control of Muscle Contraction (Neuromuscular junction) Tendons Connect Muscle to Bone Tendon Ruptures Terminology Sprain: when a ligament is stretched too much Strain: when a muscle or tendon is stretched too much