Pectoralis major

A large muscle located in the upper chest, crucial for arm movement and stability.

Pectoralis major is a thick, fan-shaped muscle that spans from the chest to the upper arm. It consists of two parts: the clavicular head, which originates from the clavicle, and the sternal head, which originates from the sternum and the cartilage of the first six ribs. This muscle mainly acts to move the arm toward the body and rotate it inward.

Terminologia Anatomica

musculus-pectoralis-major

System

Muscular system

Function

The pectoralis major plays several vital roles in the musculoskeletal system, primarily facilitating movement in the shoulders and arms. It is essential for a variety of pushing, pulling, and lifting activities. When contracted, the pectoralis major allows the upper arm to adduct (move towards the body), flex (raise), and medially rotate (turn inwards). These movements are crucial for everyday tasks such as lifting objects, performing push-ups, and engaging in sports, particularly those that involve throwing or pushing actions. The muscle also plays a significant role in stabilizing the shoulder joint, which is essential for maintaining proper posture and preventing injuries.

Location

The pectoralis major is located in the anterior (front) portion of the thorax. It covers a significant area of the chest, situated beneath the skin, and lies over the pectoralis minor muscle. The muscle’s origins are at the clavicle and the sternum, extending laterally to insert at the humerus bone of the arm. This strategic placement allows it to effectively control the movements of the upper arm while also contributing to the overall structure and aesthetics of the chest.

Did You Know?

The pectoralis major is one of the largest muscles in the upper body, playing a crucial role in many upper body movements.
Bodybuilders often focus on this muscle group as it significantly contributes to the 'chest' appearance, making it a target for various strength training exercises.
In addition to its primary functions, the pectoralis major can also assist in deep breathing by helping to expand the ribcage.