Pectoralis minor

Template:Short description Template:Infobox muscle Pectoralis minor muscle (Template:IPAc-en) is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major in the human body. It arises from ribs III-V; it inserts onto the coracoid process of the scapula. It is innervated by the medial pectoral nerve. Its function is to stabilise the scapula by holding it fast in position against the chest wall.

StructureEdit

AttachmentsEdit

From the muscle's origin, the muscle's fibers pass superiorly and laterally, converging to form a flat tendon.

OriginEdit

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.<ref name=":0">Template:Cite book</ref>

InsertionEdit

Its tendon inserts onto the medial border and upper surface of the coracoid process of the scapula.<ref name=":0" /><ref>Template:Cite book</ref>

InnervationEdit

The muscle receives motor innervation from the medial pectoral nerve.<ref name=":02">Template:Citation</ref>

RelationsEdit

Pectoralis minor muscle forms part of the anterior wall of the axilla.<ref>Template:Cite book</ref> 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.<ref>http://www.teachmeanatomy.com/muscles-of-the-pectoral-region/ Template:Dead link</ref>

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<ref>Template:Cite journal</ref> (in contrary sequence compared to the nodes) - first part medial, second part deep/posterior, third part lateral in relation to the pectoralis minor.

VariationsEdit

File:Braus 1921 137.png

An individual with an axillary arch as well as sternalis 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.<ref>Template:Cite journal</ref>

FunctionEdit

Pectoralis minor muscle depresses the point of the shoulder, drawing the scapula superior, towards the thorax, and throwing its inferior angle posteriorly.