Appendicular Skeleton and Pectoral Girdle Notes

Module 1: Skeletal System

Topic 1.3: Appendicular Skeleton
Overview
  • Focus: Bones of the limbs and girdles
  • Scope: Pectoral girdle and bones of the upper limb
  • Learning outcomes:
    • Describe composition and attachment of the pectoral girdle to the axial skeleton.
    • Identify structural features of scapula and clavicle.
    • Identify structural features of humerus, radius, ulna, and wrist/hand bones.
Pectoral Girdle
  • Definition: Attaches upper limb to skeleton. Composed of:
    • Clavicle (anterior)
    • Scapula (posterior)
  • Importance of Girdle:
    • Encircles the body.
    • Provides mobility vs. stability.
  • Comparison:
    • Pelvic Girdle:
    • Larger
    • Thicker and sturdier
    • Completely enclosed ring; prioritizes stability.
    • Pectoral Girdle:
    • Lightweight
    • Not a closed ring
    • Allows greater mobility at the expense of stability.
Clavicle
  • Shape: S-shaped collarbone
  • Function:
    • Acts as a brace to hold scapulae and arms away from rib cage, preventing anterior collapse of the shoulder.
    • Attaches to the sternum via the sternoclavicular joint (only bony attachment to axial skeleton).
  • Ends:
    • Sternal End: Cone-shaped, more medial
    • Acromial End: Flattened, more lateral
  • Injury: Common fractured bone in contact sports. A fracture leads to shoulder collapse.
Scapula
  • Shape: Triangular bone, lies flat against rib cage.
  • Borders: Superior, lateral, medial.
  • Key Features:
    • Coracoid Process: Muscle attachment point (biceps brachii)
    • Glenoid Cavity: Articulates with the humerus.
    • Subscapular Fossa: Anterior surface, lies against the rib cage.
    • Spine of the Scapula: Prominent feature, ends in acromion process (articulates with clavicle).
    • Fossae:
    • Supraspinous Fossa: Holds supraspinatus muscle.
    • Infraspinous Fossa: Holds infraspinatus muscle.
    • Subscapular Fossa: Holds subscapularis muscle.
Humerus (Brachium)
  • Articulations:
    • Shoulder joint (with scapula)
    • Elbow joint (with radius and ulna)
  • Key Features:
    • Head of Humerus
    • Anatomical Neck
    • Surgical Neck: Common fracture site.
    • Greater and Lesser Tubercle: Muscle attachment sites, separated by intertubercular groove (biceps tendon).
    • Deltoid Tuberosity: Where deltoid muscle attaches.
    • Olecranon Fossa: Indentation for olecranon process (ulna).
    • Epicondyles: Lateral and medial as attachment points for forearm muscles.
Radius and Ulna (Forearm)
  • Orientation: Anatomical position - palms forward.
    • Radius: Lateral side, thin proximal, wider distal.
    • Features include:
      • Radial Head: Proximal end.
      • Radial Tuberosity: Attachment for biceps brachii.
      • Radial Styloid Process: Distal end, prone to fractures.
    • Ulna: Medial side, broader proximal end, thin distal end.
    • Olecranon Process: Forms elbow with humerus.
    • Interosseous Membrane: Ligament connecting radius and ulna.
Wrists, Metacarpals, and Phalanges
  • Wrist Joint: Articulation between radius and eight carpal bones.
    • Carpal bones connect to five metacarpals in the palm.
  • Metacarpals:
    • Each has a base (articulates with carpals) and a head (articulates with phalanges).
    • Phalanges: 3 per finger (proximal, middle, distal), 2 in thumb.
  • Knuckles: Formed by joints between phalanges.
Summary of Topic 1.3: Appendicular Skeleton - Pectoral Girdle and Upper Limb
  • Attachment: Upper limb connected to axial skeleton via pectoral girdle (scapula & clavicle).
  • Articulations: Humerus to scapula, radius/ulna to carpals.
  • Carpal, Metacarpal, and Phalange Structure: Wrist and hand formation.
  • Key Concepts: Sacrificing stability for mobility in the pectoral girdle, detailed anatomy of each bone, important muscle attachments.