1. Skeletal Muscle Tissue Anatomy Pages 283-287

3. The connective tissue sheaths of the epimysium, perimysium, and endomysium are continuous with one another and the tendon which attaches the muscle to the bone. These sheaths contribute to muscle elasticity, provide entry and exit routes for nerves and blood vessels, harness the forces of contraction, and reinforce the muscle as a whole.

4. The arrow points out the perimysium. The asterisk is at the center of a fascicle. Notice the peripheral nerve in lower left corner.

5. Healthy adult (left) and child muscle tissue at 200x magnification. Notice the size difference of muscle fibers.

6. In this healthy adult muscle tissue, notice the darkly stained nuclei (100s per fiber) and the rather inconspicuous endomysium.

7. Muscular Dystrophy: the name given to a group of diseases that are, for the most part, genetically determined and cause gradual wasting of muscle with accompanying weakness and deformity.

8. Myopathic changes. In this case, histopathology of the gastrocnemius shows Duchenne muscular dystrophy. The muscle fibers are being replaced by adipose tissue.

9. Endomysial fibrosis is another form of muscular distrophy.

10. The muscle cell a.k.a. “fiber” is a long cylindrical cell with… Many nuclei Sarcolemma: cell membrane Sarcoplasm: cytoplasm Myofibrils:-(100s to 1,000s per fiber) -contractile element of cell. -80% of cell by volume.

11. Muscle cell showing features from previous slide. Notice the striated appears of cell.

12. The sarcomere is the contractile unit of the muscle cell and gives it’s striated appearance.

13. A. Myosin molecule: B. Thick filament: C. Filamentous actin: D. Tropomyosin: E. Globular actin:

15. Sarcolemma: Possesses a transmembrane potential that allows for electrical impulse to flow across the surface of the entire muscle fiber. Sarcoplasmic reticulum (SR): Stores Ca 2+ ions. Plays a key role in muscle contraction. T tubules: Conduct action potentials ( a.k.a. impulses) through out the muscle fiber.

16. Sliding Filament Model of Contraction: During muscle contraction thin (actin) filaments slide past thick (myosin) filaments so that actin and myosin overlap to a greater degree. – H and I bands narrow – Z discs move closer together – Overall length of fiber and muscle shortens