Proximal attachments: anterior ribs 3-5

Distal attachment: coracoid process of scapula

Actions

• Stabilization of scapula to allow for efficient movements at other joints, specifically the glenohumeral joint

• Protraction (moving the scapula anteriorly)

Innervation: medial pectoral n.

Dominant arterial supply: thoraco-acromial a. (branch of axillary a.) branches

Anatomical relationships:

• Medial pectoral n. pierces the pectoralis minor m.

• Important anatomical landmark locating branches of the axillary a. both in the lab, in imaging, and in surgeries

  • Subdivides the artery into 3 parts based on relationship to the muscle (medial, deep, or lateral to)

Clinical considerations:

• Breast pathology & surgery

  • Due to the close anatomical relationship, pectoral fascia and muscle can be affected or resected

Proximal attachments: Ribs 1-8

Distal attachment: anterior surface of scapula

Actions:

• Protraction of scapula

• Upward rotation of glenoid fossa

  • Important for allowing full range of motion for the glenohumeral (shoulder) joint, particularly in abduction and flexion

• Stabilization of scapula

Innervation: long thoracic n.

• The placement of this nerve is unique in that it is superficial to the muscle

Anatomical relationships:

• Forms the medial wall of the axilla

Clinical considerations:

• With injury to the long thoracic n., the scapula may develop a wing-like appearance (‘winged scapula’)

  • The medial border of the scapula is displaced posteriorly and laterally in comparison to the uninjured side. This is particularly evident when the shoulder joint is flexed (as in pushing against a wall with the upper limb).

  • This affects scapular motion, but (more importantly) prevents full range of motion at the glenohumeral joint