Pectoralis Minor Muscle

Origin

The pectoralis minor muscle originates from the:

- external surface of the anterior ends of the third, fourth and fifth ribs, close to their costal cartilages;

- fascia covering the external intercostal muscles.

There can be variations between individuals regarding the numbers of origin sites and the ribs to which they attach.

Insertion

The fibers of the pectoralis minor muscle travel superolaterally and insert, via a short flat tendon, onto the medial aspect of the coracoid process of scapula.

Key Features & Anatomical Relations

The pectoralis minor muscle is found in the pectoral region of the thorax. It is a triangular convergent type of skeletal muscle. It is located:

- anterior (superficial) to the third to fifth ribs and the serratus anterior and external intercostal muscles;

- posterior (deep) to the pectoralis major muscle and the pectoral branches of thoracoacromial artery;

- medial to the lateral thoracic artery;

- lateral to the third to fifth costal cartilages.

The medial pectoral nerves pierce the pectoralis minor muscle. For descriptive purposes, the axillary artery is divided into three parts, based on its anatomical relationship with the pectoralis minor muscle:

- the first part is located proximal to the medial border of the muscle;

- the second part is located posterior to the muscle;

- the third part is located distal to the lateral border of the muscle.

Actions

The pectoralis minor muscle is involved in multiple actions:

- protracts the pectoral (shoulder) girdle at the acromioclavicular and sternoclavicular joints;

- downwardly rotates the pectoral girdle at the acromioclavicular and sternoclavicular joints;

- assists in depression of the pectoral girdle at the acromioclavicular and sternoclavicular joints;

- may act as an accessory muscle of inspiration (Standring, 2016).

List of Clinical Correlates

- Poland’s syndrome

References

Moore, K. L., Dalley, A. F. and Agur, A. M. R. (2009) Clinically Oriented Anatomy. Lippincott Williams & Wilkins.

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.

Actions

The pectoralis minor muscle is involved in multiple actions:

- protracts the pectoral (shoulder) girdle at the acromioclavicular and sternoclavicular joints;

- downwardly rotates the pectoral girdle at the acromioclavicular and sternoclavicular joints;

- assists in depression of the pectoral girdle at the acromioclavicular and sternoclavicular joints;

- may act as an accessory muscle of inspiration (Standring, 2016).