Microscopic and Gross Anatomy of Skeletal Muscle

Myology Summary

  • Muscle Composition:

    • Myo-muscle

    • Muscle Fiber: Composed of myofibrils.

    • Bundling: Muscle proper consists of bundles of fascicles.

  • Muscle Function:

    • Muscles contract and exert force, opposing another muscle's action.

    • Insertion moves towards the origin during contraction.

Microscopic and Gross Anatomy of Skeletal Muscle

Key Structures

  • Myofilament: Very fine structure.

  • Actin: Thin myofilament.

  • Myosin: Thick myofilament.

  • Sarcomere: Smallest contractile unit of muscle, located between two Z-discs on myofibrils.

  • Myofibril: Bundle of myofilaments.

  • Fascicle: Bundle of muscle fibers.

  • Endomysium: Covers individual muscle fibers.

  • Perimysium: Covers fascicles.

  • Epimysium: Covers the entire muscle.

  • Tendon: Attaches muscle to bone; cord-shaped, fibrous connective tissue.

  • Aponeurosis: Attaches muscle to muscle; broad sheet of connective tissue.

Types of Muscles

  • Agonist: Primary muscle responsible for a specific movement.

  • Antagonist: Muscle that opposes the action of the agonist.

  • Synergist: Assists the agonist in performing its action.

  • Fixator: Stabilizes a structure allowing motion to occur elsewhere.

Naming Criteria for Skeletal Muscles

  • Direction: E.g., rectus abdominis, transversus abdominis.

  • Relative Size: Maximus (largest), minimus (smallest).

  • Location: E.g., biceps brachii, rectus femoris.

  • Number of Origins: Referencing muscles with multiple origins.

  • Origin and Insertion Location: Naming from specific locations.

  • Shape: E.g., deltoid, rhomboid, trapezius.

  • Action: E.g., flexor carpi radialis, extensor digitorum, adductor magnus.