10/09/2024
The pectoralis major is a large, fan-shaped muscle located in the chest. It plays a key role in the movement of the shoulder joint.
1. Origin:
The pectoralis major originates from three main areas:
• Clavicular head: The anterior surface of the medial half of the clavicle.
• Sternal head: The anterior surface of the sternum.
• Abdominal head: The superior six costal cartilages and the aponeurosis of the external oblique muscle.
2. Insertion:
It inserts at the lateral lip of the bicipital groove (intertubercular sulcus) of the humerus.
3. Nerve supply:
The pectoralis major is innervated by the medial and lateral pectoral nerves:
• Clavicular head: Lateral pectoral nerve (C5-C7).
• Sternal head: Medial pectoral nerve (C8-T1).
4. Actions:
The pectoralis major performs several important movements:
• Adduction: Moves the arm toward the body.
• Medial rotation: Rotates the arm inward.
• Flexion (clavicular head): Raises the arm in front of the body.
• Extension (sternal head): Helps extend the arm from a flexed position.
The pectoralis major is important for upper body strength and is active in pushing, lifting, and pulling movements. It stabilises the shoulder joint and assists in movements like pushing against resistance or climbing.
This muscle forms the bulk of the chest and is a key muscle for upper body aesthetics and functionality.
