Pectoralis major muscle

Pectoralis Major Muscle

The Pectoralis Major is a thick, fan-shaped muscle situated at the anterior chest wall. It is a key muscle involved in the movement of the shoulder joint, with its primary functions being the flexion, adduction, and internal rotation of the humerus. The pectoralis major is crucial not only for physical activities involving the upper body but also plays a significant role in the respiratory process.

Anatomy

The Pectoralis Major muscle originates from two distinct areas: the clavicular head, which originates from the anterior surface of the clavicle, and the sternal head, which originates from the anterior surface of the sternum, the superior six costal cartilages, and the aponeurosis of the external oblique muscle. These fibers converge towards their insertion point at the humerus.

The muscle is innervated by the medial and lateral pectoral nerves, which stem from the brachial plexus. Its blood supply is primarily through the pectoral branch of the thoracoacromial artery and the lateral thoracic artery.

Function

The Pectoralis Major has several key functions:

• Flexion of the shoulder: It brings the arm forward and upward.
• Adduction of the shoulder: It draws the arm toward the body’s midline.
• Internal rotation of the humerus: It rotates the arm towards the body.
• Assists in deep inspiration: When the shoulders are fixed, it can pull the ribcage upwards, aiding in deep inhalation.

Clinical Significance

Injuries to the Pectoralis Major muscle, such as strains or tears, are common in athletes and can significantly impact upper body movement and strength. Surgical repair is often required for complete tears. The muscle is also a common site for intramuscular injections, and its prominence makes it a key area for cosmetic and reconstructive surgery.

Rehabilitation

Rehabilitation exercises for the Pectoralis Major typically focus on strength and flexibility. Gradual resistance training and stretching exercises are essential components of recovery from injury. It is crucial to follow a healthcare provider's guidance to avoid exacerbating the injury.

See Also

• Muscular system
• Shoulder joint
• Thoracoacromial artery
• Brachial plexus