Pectoral muscles

Hey, everyone. It’s Matt from Kenhub! And in this tutorial, we will discuss the area, anatomy, and function of the pectoral muscles.

The pectoral muscles consist of the pectoralis major and the pectoralis minor, which are fan-shaped muscles of the shoulder. They shape the anatomy of the breast.

The pectoralis minor lies under the pectoralis major and both form the anterior wall of the axilla where they can be palpated.

The innervation is carried by the medial and the lateral pectoral nerves (direct branches of the brachial plexus). The pectorals are located close in relation to the brachial plexus, and both the subclavian artery and vein, which all run between the muscle and the rib cage.

The pectoralis major muscle is the most important muscle for the adduction and anteversion of the shoulder joint, which is why it is also known as the breaststroke muscle. It rotates the upper arm outwards and makes a powerful stroke movement called retroversion when the arms are elevated or, for example, in wood chopping.

If the arms are fixed, the muscle lifts the trunk, which can be helpful in climbing or during inspiration.

The pectoralis minor has two main functions. On one hand, it pulls the scapula anteriorly and inferiorly toward the ribs, known as abduction and depression respectively. This leads to a dorsomedial movement of the inferior angle of the scapula. This movement is both helpful when retracting the elevated arm as well as moving the arm posteriorly behind the back.

On the other hand, the pectoralis minor elevates the third to fifth ribs, given a fixed scapula, and expands the ribcage. By those means, it can also serve as an accessory muscle during inspiration.