Pectoralis minor m.

The pectoralis minor is a thin, triangular muscle situated anteriorly on the upper part of the chest, beneath the pectoralis major. 

It arises from the upper margins and outer surfaces of the third, fourth, and fifth ribs near their cartilages, and from the aponeuroses covering the intercostal muscles. The fibers pass superior and lateral, converging to form a flat tendon that inserts onto the medial border and upper surface of the coracoid process of the scapula.

The pectoralis minor muscle is covered anteriorly (superficially) by the coracoclavicular (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. 

The pectoralis minor depresses the point of the shoulder, drawing the scapula inferior and medial, towards the thorax, and throwing its inferior angle posteriorly.