Pectoralis minor (shown in red).
Pectoralis minor muscle (shown in red). The bone shown in blue is the shoulder blade.
|Origin||Third to fifth ribs, near the costochondral junction|
|Insertion||Medial border and superior surface of the coracoid process of the scapula|
|Artery||Pectoral branch of the thoracoacromial trunk|
|Nerve||Medial pectoral nerve (C8)|
|Actions||Stabilizes the scapula by drawing it inferiorly and anteriorly against the thoracic wall, raises ribs in inspiration|
|Latin||Musculus pectoralis minor|
|Anatomical terms of muscle|
The pectoralis minor muscle is covered anteriorly (superficially) by the clavipectoral fascia. The Medial pectoral nerve pierces the pectoralis minor and the clavipectoral fascia. In attaching to the coracoid process, the pectoralis minor forms a 'bridge' - structures passing into the upper limb from the thorax will pass directly underneath.
Axillary nodes are classified according to their positions relative to the pectoralis minor muscle. Level 1 are lateral, Level 2 are deep, Level 3 are medial. The pectoralis minor divides the axillary artery into three parts (in contrary sequence compared to the nodes) - first part medial, second part deep/posterior, third part lateral in relation to the pectoralis minor.
The origin is from the second, third and fourth or fifth ribs. The tendon of insertion may extend over the coracoid process to the greater tubercle. It may be split into several parts. Absence of this muscle is rare but happens with certain uncommon diseases, such as the Poland syndrome.