Pectoralis Major

Pectoralis major derives from the Latin word “pectus,” meaning breast is a broad, fan-shaped convergent muscle in the pectoral region and the most exterior ones. Pectoralis major is a paired muscle located at the fore surface of the thoracic cage. Bodybuilders call pectoral muscle pecs muscle. According to its origin, it is categorized into three types; clavicular, sternocostal, and abdominal. The pectoralis major is responsible for deep enforced breathing inspiration but not expiration.

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Pectoralis Major Origin and Insertion:

The pectoral muscle is made of two heads, the clavicular and the sternocostal head. The former originates from the fore surface of the medial half of the clavicle, and the latter is larger of the two. Sternocostal head originates from the anterior surface of manubrium, superior six costal cartilages, the body of the sternum, and from the outside part of the external oblique muscle. All three parts of pectoral muscle laterally coverage and pectoralis major insertion to the greater the tubercle of the humerus (the largest and longest bone of the upper limb). Pectoralis major origin from the medial half of the clavicle and from upper costal cartilages (1-6) and the aponeurosis of the external oblique. 

Functions:

Pectoralis major muscle overall function is adduction and internal rotation of the arm on the shoulder joint. The movement of adduction is closely associated with the median plane. This movement usually occurs on the anterior plane around an anteroposterior axis. Legs and arm movements are classic examples of adduction and abduction movements. The arm and leg move relative to the shoulder and hip, respectively. The clavicular part of the Pectoralis major muscle helps the arm to flex up to 90 degrees, and the sternocostal part aids the extension of the flexed arm pulling down. Pectoralis major functions are internal arm rotation, arm adduction around the shoulder joint, and arm flexion and extension.

Nerve and Blood Supply 

Pectoralis major nerve supply comes from the brachial plexus. C5, C6, C7 are lateral pectoral nerves to the clavicular head, and C8, T1 medial pectoral nerve to the sternocostal head, which stems from the brachial plexus. The brachial plexus is a network of nerves from where all motor and sensory nerves of the upper extremity derive. The pectoral branches of the thoracoacromial artery supply blood to the Pectoralis major muscle. The perforating branches of the internal thoracic artery also vascularize the pectoral muscle. The thoracoacromial artery is a short artery arising from the axillary artery.

Pectoralis Minor

The Pectoralis minor lies below the Pectoralis major muscle and both constitute the anterior part of the axilla region. The pectoralis minor originates from the third to fifth ribs and inserts into the scapula; it stabilizes the scapula by drawing it anteroinferior against the thoracic wall.

Pectoralis Major Pain

Pectoralis major pain occurs when an individual pushes a heavy object away from his chest. This phenomenon can occur while weight training or bench press exercises. During bench press exercise, the muscle requires a substantial amount of strength to lift the lower part of the bar coupled with overstretching of the muscle. The combined effects insert too much pressure on the pectoralis major, which can result in muscle tear or scar. The first symptom of pectoralis major muscle tear is abrupt pain. The pain generally starts from the armpit region and is sometimes experienced across the chest. At the same time, the person experiences something tearing inside the chest. 

In Pectoralis major pain, the person may continue with the activity with minor pain experience. The pain may gradually increase as the muscle cools down with bleeding and swelling around the wounded muscle. The pectoralis major becomes stiff and taut. These other symptoms may arise, such as reduced range of movement, rigidity, weakness, swelling/inflammation, and numbness in that area.

Pectoralis major stretch is beneficial for pectoralis major/minor muscle. A person should stretch his arm and put his palm on the wall, and rotate his body, ten to fifteen seconds on each side; this exercise is for pectoralis major. A person must stand in the doorway with one foot before the other. Then the person must bend the elbow to 90 degrees and place each forearm on each side of the entrance. A shift of weight on the extended leg will insert stretch on the chest muscle; ten to fifteen seconds is recommended for each leg. This stretch exercise is for pectoralis minor.

Hopefully, this article has helped you understand all about Pectoralis Major in detail.