Pectoralis minor muscle
|Pectoralis minor muscle|
|3rd to 5th rib|
|Coracoid process of the scapula|
|pulls the shoulder diagonally forward and down|
|Nervi pectorales medialis and lateralis|
The pectoralis minor muscle ( lat. For "smaller chest muscle") is a human skeletal muscle that is derived from the pectoralis major muscle and by which it is completely covered. In quadruped mammals, the relationship between the two chest muscles is reversed: the superficial pectoralis superficialis muscle is much weaker than the deep chest muscle ( pectoralis profundus ) below .
It has its origin on the 3rd to 5th rib, approx. 1 to 2 cm from the bone-cartilage border, sometimes also on the 2nd or 6th rib, and extends up to the coracoid process (raven's bill) of the shoulder blade. This makes it the only shoulder girdle muscle that does not attach to the free upper extremity.
On the one hand, the muscle pulls the shoulder diagonally forward and down. In addition, it causes the shoulder blade to rotate inward and serves as an auxiliary breathing muscle when the upper arm and shoulder blade are fixed . The pectoralis minor muscle is innervated by the medial and lateral pectoral nerves (C6-C8) from the brachial plexus .
In the case of paralysis of the pectoralis minor muscle, the arms raised to the horizontal can no longer be crossed. It is also no longer possible to bring the hand on the paralyzed side to the back of the other shoulder. In the pectoralis minor syndrome , severe abduction and retroversion lead to narrowing and functional damage to the brachial plexus and the axillary artery, which, however, rarely cause permanent damage. An irritation of the insertion tendon (insertion tendinosis) occurs especially in throwing sports, handball players and tennis players. The forceful over-splaying of the arm can even tear off the insertion tendon of the pectoralis minor muscle.
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