Introduction
Musculus pectoralis major means translated as “large pectoral muscle“-and this is already quite clear what it is. The musculus pectoralis major is the largest and strongest part of our front shoulder muscles. Because it is so large, it can be divided into three parts: the pars clavicularis (the part near the collarbone), the pars sternocostalis (the part near the ribs and sternum) and the pars abdominalis (which is located approximately above the abdomen). The muscle fibers of the strong pectoralis major muscle pull in a fan shape from the shoulder towards the muscle origin, i.e. to where the tendon has grown together. At the top, where the muscle attachment is, the muscle is slightly twisted in its course, so that the originally lower fibers coming from the abdominal region attach to the upper part of the crista tuberculi majoris, a bony projection at the top of the upper arm, and the previously upper muscle fibers from the bowl bone now attach to the lower part of the crista tuberculi majoris.
Function
Once the course of the entire muscle and its individual parts has been clarified and, if possible, followed with the finger on an anatomical drawing, its task and function is relatively easy to understand. On the one hand, the pectoralis major muscle is responsible for adduction (movement towards the body) of the arm, especially when the arm is in the so-called elevation position (i.e. when the arm is already raised to an angle of more than 90° in the shoulder joint). On the other hand, it takes over the inward rotation of the arm.
The pars clavicularis of the pectoralis major muscle is particularly helpful when lifting the arm forward, because it can then pull the trunk to the arm when the arm is firmly fixed (as is necessary for pull-ups, for example). As already mentioned, the muscle origin is located at the clavicle (the collarbone), the 2nd to 7th ripple cartilage and at the anterior leaf of the rectus sheath (meaning the order part of the outer muscle sheath of the large abdominal muscle). The muscle attachment of the pectoralis major muscle is at the crista tuberculi majoris humeri (the large humerus). The entire muscle is innervated by the medial pectoralis nerve and the lateral pectoralis nerve.
