Attachments From the muscle's origin, the muscle's fibers pass superiorly and laterally, converging to form a flat tendon.
Origin Pectoralis minor muscle arises from the upper margins and outer surfaces of the 3rd, 4th, and 5th
ribs near their
costal cartilages, and from the
aponeuroses covering the
intercostalis.
Insertion Its tendon inserts onto the medial border and upper surface of the
coracoid process of the
scapula.
Innervation The muscle receives motor innervation from the
medial pectoral nerve.
Relations Pectoralis minor muscle forms part of the anterior wall of the
axilla. It 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.
Variations muscle and an accessory abdominal portion of the
pectoralis major. 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. == Function ==