Last update: Dec 7th, 2017

Pectoralis Major Muscle – Attachment, Action & Innervation

Pectoralis Major Muscle

Pectoralis major is a thick, fan-shaped muscle contributing to the thoracobrachial motion. It consists of a clavicular part and a sternal part, both converging to a flat tendon that inserts on the humerus. It’s innervated by both medial and lateral pectoral nerves.

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Attachments of Pectoralis Major Muscle: Origin & Insertion

Origin: (proximal attachments)
a. Clavicular head: medial half of the clavicle.
b. Sternal head: sternum, upper costal cartilages (1-6), and the aponeurosis of the external oblique.

Insertion: (distal attachments)
a. Lateral lip of the intertubercular (bicipital) groove of the humerus.
b. Crest of the greater tubercle of the humerus.

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Actions of Pectoralis Major Muscle:

Clavicular head:

Flex the arm at the shoulder (glenohumeral) joint.

Sternal head:

Extends the arm  at the shoulder (glenohumeral) joint from a flexed position.

Both heads working together:

a. Medially rotate the arm at the shoulder (glenohumeral) joint.

b. Adduct the arm at the shoulder (glenohumeral) joint.

Innervation of the Pectoralis Major:

Nerves to the muscle:

Nerve roots:

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