Transcript SSN MUSCLE
MUSCLE Histology SSN October 17, 2005 Presented By: Tabassum Sardharwala & Shannon Watkins Muscle Types Which is Which? Cardiac? Skeletal •Striated •Voluntary Skeletal? Smooth? Smooth •Smooth •Involuntary Cardiac •Striated •Involuntary What other places can “skeletal” muscle be found? Skeletal Muscle Cross section • Endomysium • Perimysium • Epimysium Skeletal Muscle Organization Ross Fig 10-3 (p.250, 4th ed.) How do Muscles get their Stripes? • Light band is the I band = actin only – Actin anchored at the Z disc at center of I band • Dark band is the A band = myosin + overlapping actin – Contains H band = myosin only – Myosin anchored at the M line When Muscles Contract… • The A band does NOT change length • H and I bands shrink • Z discs are drawn closer together • Actin & myosin filaments do not actually shorten, they just slide past each other The Triad • Triad = 1 T tubule + 2 terminal cisternae of the sarcoplasmic reticulum • There are 2 triads per sarcomere (in skeletal muscle) located at the ends of the A band (A-I junctions) • Function- Depolarization of sarcolemma (T tubule) triggers Ca2+ release from sarcoplasmic reticulum to initiate contraction Motor End Plates Motor unit = motor nerve + muscle cells it innervates Other Things to Know Muscle-tendon Junction Cardiac Muscle Like skeletal muscle, cardiac muscle has: • Sarcomeres (striations) • T-tubules • Calcium regulation at level of thin filaments So what’s different? Lab 7 Slide 13 Cardiac Muscle – Defining Characteristics Branching myofibrils Large, central, ovoid nuclei Intercalated Disks Lab 7 Slide 14 Intercalated Disks Lab 7 Slide 16 Also, T Tubules and SR arranged in a diad, not triad Which is which? Cardiac Skeletal Which is which? Lab 7. Slide 15. Cardiac Lab 17. Slide 10. Skeletal Smooth Muscle Located in blood vessels, ducts, and here, in the GI tract. (This is the colon.) Lab 7 Slide 17 Smooth Muscle Longitudinal section ? Myenteric Ganglion Cross Section A Closer Look Elongated nuclei Indistinct boundaries (w/ H&E) Wrinkled nuclei Centrally located nuclei Lab 7 Slide19 Smooth Muscle Cardiac Muscle Smooth Muscle vs. CT Smooth Muscle •Darker Staining •Nuclei within fibers •Wrinkled nuclei DIACT •Lighter Staining •Fewer nuclei, outside fibers Lab 4. Slide 16. Smooth Muscle v. CT Smooth Muscle DRACT Silver Stain Clear Basal Lamina Lab 7 Slide 23 A Closer Look – Why the “Dotted Lines”? Interrupted basal lamina due to GAP JUNCTIONS •Ensure coordination during contraction Lab 7 Slide 24 What Muscle?? Smooth Nerve Skeletal Lab 17. Slide 14 Esophagus – Where Smooth and Skeletal Muscle Combine 1. A B 2. 3. A B C D 4. 5.