1. Chapter 34 THE MUSCULOSKELETAL SYSTEM

2. A. Types of Skeletons 1. Hydrostatic skeleton Consists of liquid within a layer of flexible tissue. Functions to provide shape & allow movement. Ex. hydra, jellyfishes, sea anemones, slugs & annelids

3. 2. Exoskeleton A braced framework skeleton on the outside of organism. Functions to provide shape, protection & sites for muscle attachment. mollusks (calcareous shells that enlarge as animal grows) arthropods (chitinous shells that must be periodically molted)

4. 3. Endoskeleton A braced framework skeleton on the inside of organism. sponges (calcareous or silica spicules) echinoderms (calcareous plates) vertebrates (primarily bone; cartilage in some)

5. Functions of the Vertebrate Skeleton F support F protection F lever system for movement F production of blood cells F mineral storage Vertebrate skeletons are similar, but exhibit species specific adaptations.

6. Tissues of the Vertebrate Skeleton Cartilage ] consists of chondrocytes embedded in a collagen/elastin matrix ] located at ends of long bones & between vertebrae ] functions as shock absorber Bone ] consists of osteocytes embedded in a mineralized collagen matrix ] good blood supply ] constantly being remodeled

7. Spongy bone ] found in expanded ends of long bones & flat bones ] contains red marrow Compact bone ] found in shaft of long bones ] contains yellow marrow Presence of spongy bone & marrow cavity reduces bone weight. Marrow cavity

8. B. Human Skeleton Axial skeleton ] skull ] vertebral column F 7 cervical vertebrae F 12 thoracic vertebrae F 5 lumbar vertebrae F 1 sacrum F 1 coccyx ] ribs - 12 pair in both males & females ] sternum skull sternum ribs vertebral column

9. Appendicular skeleton ] pectoral girdle F clavicles F scapulae ] pelvic girdle F pelvic bones ] upper appendages (arms) ] lower appendages (legs) clavicle scapula humerus radius ulna pelvic bone femur patella tibia fibula

10. C. Muscle Diversity Animal muscles are composed primarily of the proteins actin & myosin. 1. Smooth muscle ] spindle-shaped cells ] uninucleate ] nonstriated ] involuntary Adductor muscle of bivalve mollusks; walls of blood vessels; iris of eye; walls of hollow organs (stomach, intestines, bladder).

11. 2. Cardiac muscle ] Branched, uninucleate cells ] striated ] involuntary ] possess intercalated disks Unique to the heart 3. Skeletal muscle ] long, multinucleate cells ] striated ] voluntary Usually attached to skeleton

13. D. Skeletal Muscle - a closer look 1. Structure Skeletal muscles contain bundles (fascicles) of skeletal muscle fibers (cells).

14. Each muscle fiber is surrounded by a plasma membrane (sarcolemma) & contains: ] numerous mitochondria & nuclei ] extensive endoplasmic (sarcoplasmic) reticulum packed with Ca 2+ ] several myofibrils consisting of overlapping actin & myosin myofilaments.

15. 2. Contraction ] action potential triggers release of acetylcholine at neuromuscular junction ] electrical wave spreads over sarcolemma & enters muscle fiber ] sarcoplasmic reticulum dumps Ca 2+ into cytoplasm ] Ca 2+ enable actin & myosin myofilaments to slide past each other [requires ATP]

17. Muscle relaxes (myofilament sliding stops) when Ca 2+ are removed from the cytoplasm.

18. Large amounts of ATP are required for muscle contraction AND relaxation. ] breaks/reforms connections between actin & myosin ] powers pumps that return Ca 2+ to the sarcoplasmic reticulum Muscle cells generate ATP: ] from creatine phosphate ] by aerobic respiration ] by anaerobic respiration What is rigor mortis?

19. 3. Athletic performance Linked to proportion of fast-twitch and slow-twitch fibers in muscles. ] Muscles containing a high proportion of fast- twitch fibers (contract rapidly/fatigue quickly) function best in short, fast events. ] Muscles containing a high proportion of slow- twitch fibers (contract slowly/resist fatigue) function best in endurance events.

20. E. Joints Junctions between bones. Joints are classified as: ] Immovable Ex. suture ] Slightly moveable Ex. vertebrae ] Freely moveable Ex. synovial

21. Synovial joints enable muscles to interact with bones, producing movement.

22. Most common type of joint problem is arthritis (joint inflammation). ] Osteoarthritis (“wear-and-tear” arthritis) Cartilage covering the ends of bones slowly wears away, causing stiffness & soreness. ] Rheumatoid arthritis Autoimmune disease in which the body’s immune system attacks the synovial membranes.