Synonyms
Latin: Musculus pectoralis minor
History
Attachment: Processus coracoideus Origin: 2nd – 5th rib, lateral to the cartilage-bone interface Innervation: Nn. pectorales med. , C (6) – 8, Th1
Anatomy
The small pectoral muscle lies below the large pectoral muscle (M. Pectoralis major). It has its origin at the front of the 3-5th rib, about 6cm from the sternum. From there it runs to the coracoid process on the shoulder blade.
It is nerved by the medial pectoral nerve and the lateral pectoral nerve. Both are nerves of the brachial plexus, a network of nerves from the spinal nerves that leave the spinal cord at the level of the 5th cervical vertebra up to the 1st thoracic vertebra. The subclavian vein and artery runs below the base of the small chest muscle. Among other things, it serves to supply the arm with blood. The brachial plexus is wrapped around the subclavian artery.
Function
The small breast muscle (Musculus pectoralis minor) pulls the shoulder blade, along its fiber course, forward, downward. Due to its attachment to the upper front part of the shoulder blade and its origin at the middle part of the 3-5th ribs, shortening of the muscle results in a pulling of the shoulder blade forward and down. When the shoulder is fixed, the minor pectoralis muscle serves as a respiratory aid.
Fixation of the shoulder blade results in a kind of reversal of the direction of traction. This means that instead of the shoulder blade being pulled down forwards, the 3-5th rib is pulled outwards and thus helps to expand the rib cage during inspiration. Fixation of the shoulder blade can be achieved by supporting the arms, for example on the knees. Optimal support of the diaphragm by the respiratory muscles can best be achieved by bending the upper body slightly forward and supporting the arms.
Common diseases of the small pectoral muscle
The most effective and simplest method of stretching the chest muscles is to stretch against a resistance. If you want to stretch the left pectoral muscle, stand sideways next to a door frame with your left arm facing the door frame. Now stretch your left arm upwards and then bend it at a 90° angle so that your hand is pointing upwards and the palm of your hand is pointing forward.
Now press your arm against the door frame and turn your upper body to the right so that your left arm is guided further and further back. Continue doing this exercise until a feeling of stretching in the chest appears.
