Overview

The pectoralis major is the broad, powerful muscle covering the front of your chest. It crosses the shoulder and attaches to the upper arm, making it a major mover during pressing, hugging and throwing.

Location

Covers the front upper chest
Has clavicular, sternocostal and abdominal portions
Forms the front fold of the armpit as it approaches the humerus

Origin, Insertion, Nerve Supply, and Action

Origin: Medial clavicle, sternum, upper rib cartilages and external-oblique aponeurosis
Insertion: Lateral lip of the intertubercular groove of the humerus
Nerve supply: Medial and lateral pectoral nerves, C5–T1
Action: Adducts and internally rotates the arm; assists flexion and extension depending on arm position

Function

Produces force during bench press and push-ups
Pulls the arm across the body
Internally rotates the shoulder
Helps accelerate the arm in throwing

Structures It Connects To

Clavicle
Sternum and ribs
Humerus
Pectoral nerves

Movements It Assists

Horizontal adduction
Shoulder internal rotation
Pressing and pushing
Arm flexion from the side

Common Injuries

Muscle strain
Partial or complete tendon rupture, often during heavy eccentric pressing
Tendon irritation near the upper-arm attachment

Pain Referral Patterns

Symptoms are usually felt in the chest, front of the shoulder or upper arm. Bruising, a visible change in the front armpit fold and sudden weakness after heavy pressing raise concern for a significant tear.

Clinical Relevance

Pectoralis-major injuries should be distinguished from rotator-cuff, biceps and chest-wall problems. Acute deformity or marked pressing weakness after a sudden injury warrants prompt assessment.

Interesting Facts

The tendon twists before attaching to the humerus, arranging fibres from different regions into layered folds.
The clavicular and sternocostal portions can contribute differently depending on arm position.

References

StatPearls. "Anatomy, Thorax, Pectoralis Major." https://www.ncbi.nlm.nih.gov/books/NBK525991/
ElMaraghy AW, Devereaux MW. A systematic review and comprehensive classification of pectoralis major tears. https://pubmed.ncbi.nlm.nih.gov/22785612/
OpenStax. "Muscles of the Pectoral Girdle and Upper Limbs." https://openstax.org/books/anatomy-and-physiology-2e/pages/11-5-muscles-of-the-pectoral-girdle-and-upper-limbs

Pectoralis Major