The pectoralis minor is a thin muscle located near the top of the chest. It is situated close to the pectoralis major, which is found above the minor muscle. It is triangular serves the purpose of pushing the scapula forward as well as downwards. It is also required to stabilize the scapula during movement. An example of an everyday use for the muscle would be pushing open a door.
The origin of the pectoralis minor is on several of the upper ribs. It inserts at the coracoids process of the scapula and its innervation is via the medial pectoral nerve. Toward the insertion, the muscle flattens and becomes a tendon.
As with many muscles of the body, the pectoralis minor works closely with another in order to provide the required motion. In this case the muscle works with the serratus anterior. While the pectoralis minor pushes forward and downward, the Serratus anterior pushes upward. This provides movement which is known as pure protraction — movement without rotation.
The muscle is found in the upper portion of the chest and attaches to the surface of the third, fourth or fifth ribs. This varies depending on the person involved. Although complete absence of the muscle is rare it is not unheard of. In some cases the muscle may consist of several different parts although this is also relatively rare. There is sometimes a variation in where the tendon inserts although this isn’t thought to have an effect on movement or strength.
Although the pectoralis minor is an important muscle in the chest, the pectoralis major is larger and stronger. The two muscles have different actions, however, although they both have the same innervation. Instead of movement of the scapula, the purpose of the pectoralis major is to provide shoulder flexion as well as adduction. An example of this sort of movement could be applying roll on deodorant. The pectoralis major muscle can be strengthened by performing pushups.
Injuries can occur in the pectoralis minor, although problems are more likely to arise in the pectoralis major. Chest strains are relatively common injuries. These can involve sharp and sudden pain as well as swelling over the area of the muscle. To start, these injuries are usually treated by resting and applying ice although more severe injuries may require other non-surgical treatments. Operations are usually only required if there is a complete rupture.