Muscles, Bones & Joints Overview

Muscular System Overview

• The muscular system consists of over 650 skeletal muscles responsible for body movement.
• Muscles attach to bones through tendons, a type of connective tissue.
• muscle tissue is made of specialized cells capable of contraction, enabling movement.

Muscle Structure

• Muscle fibers are elongated, thin cells containing specialized cytoplasm known as sarcoplasm.
• Sarcoplasmic reticulum within muscle fibers stores calcium necessary for contraction.
• Muscle fibers are enclosed by a membrane called the sarcolemma and contain myofibrils which are essential for contraction.

Types of Muscle Tissue

• Skeletal Muscle:

  • Multinucleated, striated fibers enabling voluntary movement and maintaining posture.
  • Forms sphincters for bodily functions like swallowing and urination.

• Cardiac Muscle:

  • Found only in the heart, featuring short, branched fibers with striations and intercalated discs for rapid electrical conduction.
  • Involuntary muscle responsible for pumping blood.

• Smooth (Visceral) Muscle:

  • Located in internal organ walls, uni-nucleated, spindle-shaped, and non-striated.
  • Weakest muscle type and functions involuntarily.

Muscle Functions

• Muscles fulfill various roles during contraction:
  • Prime Movers (Agonists): Muscles that initiate a specific movement.
  • Antagonists: Muscles that oppose the action of prime movers.
  • Synergists: Aid prime movers in stabilizing movements.
  • Fixators: Maintain posture during contractions.

Muscle Naming Criteria

• Muscle names derive from several criteria:
  • Location: E.g., temporalis near the temporal bone.
  • Shape: E.g., trapezius resembling a trapezoid.
  • Size: Terms like maximus (large) and minimus (small).
  • Direction: Describes fiber orientation, e.g., rectus (parallel).
  • Origins: Number of muscle origins, e.g., biceps (two).
  • Attachment Points: Names indicate origin and insertion locations, like sternocleidomastoid.

Muscle Shapes

• Muscle fibers (fascicles) can be arranged in various shapes:
  • Circular Muscles: Concentric rings (e.g., orbicularis oculi).
  • Convergent Muscles: Spread out and converge towards a tendon (e.g., pectorals).
  • Fusiform Muscles: Tapered toward tendon ends.
  • Parallel Muscles: Fibers run parallel to the muscle's long axis (e.g., sartorius).
  • Pennate Muscles: Short fibers at angles to a tendon, including:
    • Uni-pennate: Muscle on one side of the tendon.
    • Bi-pennate: Muscle on both sides of the tendon, resembling feathers.
    • Multipennate: Multiple directions, more complex arrangement.

Explore the fundamental concepts of the muscular system, including the roles of muscles, tendons, and their connection to bones. This quiz by Dr. Tari Agbalalah will help you understand how these components work together for movement. Test your knowledge on muscle tissue and its functions.