Understanding the Human Skeletal System

Oct 28, 2024

Anatomy and Physiology of the Skeletal System

Introduction

  • The skeletal system in humans is more complex than the simplified "toe bone's connected to the foot bone" song.
  • Consists of 206 bones, cartilage, fibrous connective tissue, and joints.
  • Skeletal system enables movement through muscle contraction across joints.

Divisions of the Skeleton

  • Axial Skeleton
    • Comprises 80 midline bones: skull, vertebral column, thoracic cage.
    • Skull: 8 cranial and 14 facial bones for brain protection and sensory functions.
    • Vertebral Column: 33 irregular bones, starting with atlas vertebra, supports body, protects spinal cord.
    • Thoracic Cage: 12 rib pairs and sternum, protects vital organs, supports muscles.
  • Appendicular Skeleton
    • Includes upper/lower limb appendages, pectoral, pelvic girdles.
    • Shared setup in limbs: three major segments (one bone, two bones, lots of bones, digits).

Joints

  • Joints are critical for movement, classified by structure and function.
  • Structural Classification
    • Fibrous Joints: Dense connective tissue, mostly immovable, e.g., skull sutures.
    • Cartilaginous Joints: Bones united by cartilage, limited movement, no joint cavity.
    • Synovial Joints: Freely movable, separated by fluid-filled cavity.

Joint Movements

  • Types of Movement

    • Synarthroses: Non-moving joints, e.g., cranial sutures.
    • Amphiarthroses: Slightly moving joints, e.g., pubic symphysis.
    • Diarthroses: Fully movable joints, e.g., knees, elbows.
  • Synovial Joint Features

    • Synovial fluid acts as lubricant, prevents joint friction.
    • Six configurations of synovial joints allow diverse movements.

Specific Joint Movements

  • Gliding Movements: Flat surface glides over another, e.g., wrist joints.
  • Angular Movements
    • Flexion: Decrease joint angle, bring bones together.
    • Extension: Increase joint angle, move bones apart.
    • Abduction/Adduction: Move limb away/toward body.
    • Circumduction: Circular motion, combines flexion, extension, abduction, and adduction.
  • Rotational Movements: Bone turns around its axis, e.g., shoulder and hip joints.
  • Special Movements: Unique motions, e.g., thumb opposition, supination/pronation of palm.

Conclusion

  • Learning about the skeletal system is more effective through understanding its physiology and the various types of movements.
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