Bones of the pectoral girdle

Bones of the Pectoral Girdle

The pectoral girdle (shoulder girdle) connects the upper limb to the axial skeleton, providing support and mobility to the shoulder joint. It consists of two bones on each side:

  1. Clavicle (Collarbone)

  2. Scapula (Shoulder Blade)

Clavicle

  • Location: Horizontal bone lying above the first rib; connects the sternum to the scapula.

  • Shape: S-shaped long bone.

  • Parts:

    • Sternal end: Articulates with the manubrium of the sternum at the sternoclavicular joint.

    • Acromial end: Articulates with the acromion process of the scapula at the acromioclavicular joint.

    • Shaft: The central part of the clavicle with attachments for muscles and ligaments.

  • Functions:

    • Acts as a strut to keep the upper limb away from the thorax for greater mobility.

    • Protects neurovascular structures in the cervicoaxillary canal.

    • Transmits mechanical force from the upper limb to the axial skeleton.

Scapula

  • Location: A flat, triangular bone situated on the posterior thoracic wall, between the 2nd and 7th ribs.

  • Parts:

    • Borders:

      • Superior border.

      • Medial (vertebral) border.

      • Lateral (axillary) border.

    • Angles:

      • Superior angle.

      • Inferior angle.

      • Lateral angle (glenoid cavity location).

    • Processes:

      • Acromion: Articulates with the clavicle at the acromioclavicular joint.

      • Coracoid process: Provides attachment for muscles like the pectoralis minor and coracobrachialis.

    • Glenoid cavity: A shallow depression that articulates with the head of the humerus to form the glenohumeral joint (shoulder joint).

    • Spine of scapula: A prominent ridge dividing the scapula into the supraspinous and infraspinous fossae, sites for muscle attachment.

  • Functions:

    • Serves as an anchor for muscles of the shoulder and arm.

    • Enhances the range of motion of the upper limb.

Joints of the Pectoral Girdle

  1. Sternoclavicular Joint:

    • Connects the sternum and clavicle.

    • Synovial joint allowing multidirectional movement.

  2. Acromioclavicular Joint:

    • Connects the acromion of the scapula and the clavicle.

    • Allows gliding movements.

  3. Glenohumeral Joint:

    • Not directly part of the girdle but dependent on its stability.

    • Provides a wide range of motion to the arm.

Clinical Relevance

  • Clavicular Fractures: Common due to falls; may lead to neurovascular compromise.

  • Scapular Dyskinesis: Altered movement of the scapula affecting shoulder function.

  • Shoulder Dislocations: Often involve the glenohumeral joint but depend on the integrity of the girdle.

Would you like additional elaboration on specific muscles or diagrams to complement these notes?