Structure of Skeletal Muscle Cells

General Overview

• Skeletal muscles vary in shape and size.
• The basic structure of a skeletal muscle cell is consistent.

Muscle Protective Layers

1. Epimysium

   • Protective sheath covering the entire muscle.
   • Protects muscle from friction against other muscles and bones.
   • Continues to form tendons, along with other connective tissues, connecting muscle to bone.

2. Fasciculi

   • Bundles of muscle fibers within the muscle.
   • Each fasciculus is encased in perimysium, another connective tissue.
   • Number of fibers per bundle:
     • Large muscles (e.g., quadriceps) have many fibers.
     • Smaller muscles (e.g., hand muscles for precision) have fewer fibers.

3. Endomysium

   • Fibrous connective tissue covering each muscle fiber.
   • Provides insulation for individual muscle fibers.

Muscle Fiber Components

• Sarcolemma: Muscle fiber cell membrane, located beneath the endomysium.
• Sarcoplasm: Gelatinous fluid beneath the sarcolemma.
  • Contains glycogen and fats for energy.
  • Contains mitochondria for energy production.

Myofibrils and Muscle Contraction

• Myofibrils: Cylindrical organelles within each muscle fiber.

  • Each muscle fiber contains hundreds or thousands of myofibrils.
  • Comprised of proteins: actin and myosin.
  • Essential for muscle contraction.

• Sarcoplasmic Reticulum

  • Network of tubules and channels surrounding myofibrils.
  • Stores calcium, crucial for muscle contraction.

• Sarcomeres

  • Functional repeating segments within a myofibril.
  • Basis for the sliding filament theory of muscle contraction.

Note

• For additional insights on physical education and sports coaching, engage with related educational content.