Appendicular Skeleton Lecture Notes

Overview

• Focus on the bones of the appendicular skeleton, particularly the upper part.

Pectoral Girdle

• Components: Clavicle and Scapula.
  • Clavicle:
    • S-shaped bone.
    • Rounded, fat end articulates with the manubrium of the sternum.
    • Flattened end attaches to the acromion process.
    • To distinguish right from left, the bump (conoid tubercle) should be on the back side and down.
  • Scapula:
    • Two scapulas, smooth side articulates with rib cage.
    • Dorsal side has processes.
    • Glenoid fossa for humerus articulation.
    • Coracoid process for biceps attachment.
    • Key landmarks: Lateral margin, medial margin, spine, acromion process, glenoid fossa, coracoid process.
    • Orientation: Smooth side anterior, lateral side for arm articulation.

Humerus

• Proximal end:
  • Ball (head) articulates with the glenoid cavity.
  • Proximal end orientation.
• Distal end:
  • Large cavity (olecranon fossa) at the back.
  • Trochlea (medial condyle) for ulna articulation.
  • Capitulum (lateral condyle) for radius articulation.
  • Lateral epicondyle above capitulum; Medial epicondyle above trochlea.
  • Coronoid fossa at anterior surface for ulna coronoid process.
• Fossa:
  • Anterior: Coronoid fossa.
  • Posterior: Olecranon fossa.

Ulna

• Orientation: Ulna is on the lower part, towards the pinky.
• Key landmarks:
  • Head (distal end, exception).
  • Styloid process for muscle attachment.
  • Proximal end has U-shape for articulation with humerus.
  • Olecranon process fits into olecranon fossa of humerus.
  • Trochlear notch rides on trochlea.
  • Coronoid process fits into coronoid fossa of humerus.

Radius

• Orientation:
  • Radius is characterized by a circular head at the proximal end.
  • Forms an ‘R’ with the arm.
• Key landmarks:
  • Head is at the proximal end.
  • Radial tuberosity for muscle attachment.

Key Points:

• Clavicle's fat end is medial, smooth side of the scapula is anterior.
• Humerus orientation based on position of the olecranon fossa.
• Distinguishing ulna and radius: Ulna under and towards pinky, radius has a circular end.