Appendicular Skeleton

Overview of the Appendicular Skeleton

  • The appendicular skeleton consists of 126 bones, while the axial skeleton contains 80 bones.

Components of the Appendicular Skeleton

  1. Pectoral Girdle

    • Composed of the clavicle and scapula.
    • Key joints:
      • Acromioclavicular joint
      • Glenohumeral joint
      • Sternoclavicular joint
    • Clavicle:
      • Acromial end and sternal end
      • Important landmarks: conoid tubercle, impression for the costoclavicular ligament
    • Scapula:
      • Features: acromion, coracoid process, glenoid cavity, medial and lateral borders

  2. Upper Limb

    • Consists of the humerus, radius, ulna, carpals, metacarpals, and phalanges.
    • Humerus:
      • Anatomical neck, surgical neck, greater and lesser tubercles, deltoid tuberosity, various fossae.
    • Radius and Ulna:
      • Head of radius, neck, styloid process, olecranon, ulnar tuberosity.

  3. Carpals

    • Total of 8 carpal bones:
      • Proximal row: scaphoid, lunate, triquetrum, pisiform
      • Distal row: trapezium, trapezoid, capitate, hamate
    • Mnemonic for carpal bones: "Stop Letting Those People Touch The Cadaver's Hand"

  4. Pelvic Girdle

    • Key components: sacroiliac joint, acetabulum, obturator foramen, pubic symphysis.
    • Male vs Female Pelvis:
      • Male pelvis: larger, narrower, < 90° pubic arch angle
      • Female pelvis: rounder, wider pelvic opening for childbirth, > 90° pubic arch angle

  5. Thigh

    • The femur is the longest bone, featuring structures for muscle attachment.
    • Patella:
      • Largest sesamoid bone, increases leverage for quadriceps muscles.
      • Common injury: Runner’s knee (patellofemoral stress syndrome).

  6. Leg

    • Composed of the tibia and fibula.
    • Tibia:
      • Medial, larger, bears weight.
      • Articulates with femur (at medial and lateral condyles) and talus of the ankle at the distal end.
    • Interosseous membrane joins tibia and fibula.
    • Distal ends form the medial and lateral malleoli at the ankle.

  7. Foot

    • Composed of 7 tarsal bones to form the ankle mortise, heel, and arches.
    • Calcaneus:
      • Largest and strongest tarsal bone, forms the heel.

Conclusion

  • The appendicular skeleton plays a crucial role in movement and physical support, with specific features unique to its components allowing for functionality and stability across different activities.