Anatomy and Physiology: Microscopic Anatomy of Muscle Tissue

Lecture by Professor Long at Del Mar College

Introduction

• Focus on microscopic anatomy and histology of muscle tissue.
• Importance of understanding muscle contraction.

Structure of Skeletal Muscle

• Epimysium: Outer connective tissue of the muscle.
  • Covers the entire muscle.

Hierarchical Structure within Muscles

1. Muscle

   • Composed of bundles of smaller units called fascicles.

2. Fascicle

   • Bundled by connective tissue called Perimysium.
   • Composed of muscle fibers (muscle cells).

3. Muscle Fiber (Myofiber)

   • Also known as muscle cell or muscle fiber.
   • Contains a unique cell membrane called Sarcolemma.
   • Enveloped by Endomysium:
     • Provides electrical insulation between cells.
     • Connects muscle cells at the ends, helping to transmit force to the tendon.

Protein Structure in Muscle Cells

• Myofibrils: Subunit within muscle fibers composed of proteins.
  • Lacks connective tissue, appears as long tubes.

Myofilaments in Myofibrils

• Actin (Thin Filament)
• Myosin (Thick Filament)
  • Both form repeating units called Sarcomeres.
  • Arranged in a pattern along myofibrils.

Sarcomere Structure

• Z lines: Define the boundaries of each sarcomere.
• M line: Center of the sarcomere.

Muscle Contraction

• Sliding Filament Theory:
  • Myosin pulls on actin filaments, bringing Z lines closer.
  • Shortens sarcomeres, thus shortening the myofibril and the muscle cell.

Functionality of Connective Tissues

• Endomysium, Perimysium, Epimysium:
  • Aid in force transmission from muscle cells to tendons, leading to movement.

Conclusion

• Overview of the hierarchical structure and function of muscle tissue.
• Preview of further discussion on the molecular structure of actin and myosin in the next lecture.

This lecture provides a foundational understanding of the microscopic anatomy of skeletal muscle, essential for comprehending muscle contraction mechanisms.