Shoulder Girdle Anatomy

Chapter 6: Shoulder Girdle Anatomy

Overview of the Shoulder Girdle

  • Definition: The shoulder girdle is the structure that connects the upper limb to the trunk.
  • Components:
    • Clavicle: A long bone that serves as a strut between the shoulder blade and the sternum.
    • Scapula: A flat bone that forms the posterior portion of the shoulder and serves as the attachment point for various muscles.
    • Humerus: Although it articulates with elements of the shoulder girdle, it is not considered part of the girdle itself.

Articulations of the Shoulder Girdle

  • Primary Articulations:
    • Shoulder Joint: The humerus articulates with the scapula.
    • Sternoclavicular (SC) Joint: Articulates with the manubrium of the sternum.
    • Acromioclavicular (AC) Joint: Articulates between the clavicle and the acromion of the scapula.
  • Functionality: The shoulder girdle facilitates a wide range of motion in the upper limb and connects it to the axial skeleton.

Detailed Anatomy

Clavicle

  • General Characteristics:
    • Classified as a long bone.
    • Lies just above the first rib.
  • Extremities:
    • Acromial Extremity: Lateral end articulates with the acromion on the scapula at the AC joint.
    • Sternal Extremity: Medial end articulates with the manubrium of the sternum at the SC joint.
  • Curvature:
    • The clavicle exhibits a double curve, which is more pronounced in males than females.

Scapula

  • General Characteristics:
    • Classified as a flat bone.
    • Triangular in shape with two primary surfaces:
    • Costal surface: Anterior side facing the ribcage.
    • Dorsal surface: Posterior side.
  • Borders:
    • Lateral Border: Edge closest to the humerus.
    • Medial Border: Edge closest to the spine.
    • Superior Border: Top edge of the scapula.
  • Angles:
    • Superior Angle: The uppermost point.
    • Inferior Angle: The lowest point, where the medial and lateral borders meet.
    • Lateral Angle: Contains the glenoid cavity, which articulates with the humerus.
  • Major Features:
    • Acromion: The bony projection on the top of the scapula.
    • Coracoid Process: A smaller bony projection providing attachment for muscles and ligaments.
    • Glenoid Cavity: A shallow socket allowing the humerus to articulate, permitting various movements.
    • Spinal Features:
    • Spine of Scapula: The prominent ridge of bone on the posterior aspect.
    • Notches and Fossae:
      • Supraspinous Fossa: Above the spine, attachment for the supraspinatus muscle.
      • Infraspinous Fossa: Below the spine, attachment for the infraspinatus muscle.

Summary of Shoulder Joints

  • Types of Joints:
    • Acromioclavicular (AC) Joint: Synovial gliding joint, allowing slight movements.
    • Sternoclavicular (SC) Joint: Classified as a synovial double-gliding joint.
    • Scapulohumeral (Glenohumeral) Joint: A ball-and-socket joint, allowing a wide range of motion (flexion, extension, rotation, etc.).

Anatomical Orientation

  • Anterior vs. Posterior Aspects:
    • The anterior aspect of the shoulder girdle includes features for muscle attachment and articulation while the posterior aspect supports different muscle groups.

Review Questions

  • Clicker Question 1: What is the lateral thickened end of the scapular spine called?

    • Choices:
    • Acromion
    • Coracoid process
    • Coronoid process
    • Glenoid process

  • Clicker Question 2: The scapular notch is located on the:

    • Choices:
    • Medial border
    • Lateral border
    • Inferior border
    • Superior border

Additional Notes

  • Importance of Proximal Humeral Anatomy: Although the humerus is not part of the shoulder girdle, its proximal anatomy is essential for evaluating shoulder joints on radiographs, implying its functional interdependence with the shoulder girdle components.