Video: 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 muscle's function as a whole includes adduction and internal rotation of the arm at the shoulder joint. The muscle can be divided into two parts however, and when each of these parts is operating on its own, they perform different functions. For example, the clavicular part of the muscle helps to flex the extended arm to a 90 degree angle, while the sternocostal part helps to extend the flexed arm by pulling it downwards.

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.