Pectoralis muscles name and position image

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pectoralis major minor muscle anatomy diagram labeled

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Here is a complete, image-rich overview of the pectoralis muscles from Gray's Anatomy for Students and the THIEME Atlas of Anatomy:

Pectoralis Muscles - Name, Position & Anatomy

1. Pectoralis Major

The largest and most superficial muscle of the anterior chest wall. It forms the anterior wall of the axilla and creates the anterior axillary fold.

Pectoralis major - anterior view showing clavicular head and sternocostal part

Parts / Origin:

Part	Origin
Clavicular head	Medial half of the clavicle
Sternocostal part	Sternum + costal cartilages of ribs 1-6
Abdominal part	Anterior layer of the rectus sheath

Insertion: Crest of the greater tubercle (lateral lip of the intertubercular sulcus) of the humerus - the tendon twists on itself so the clavicular fibers insert lower than the sternocostal fibers.

Actions: Adduction + internal rotation of the arm (whole muscle); flexion (clavicular and sternocostal parts); assists respiration when the shoulder girdle is fixed.

Innervation: Medial and lateral pectoral nerves (C5-T1)

Pectoralis major - all three parts labeled with bony attachments

2. Pectoralis Minor

A small, triangular muscle lying deep to pectoralis major, against the anterior thoracic wall. It is an important surgical landmark because the brachial plexus and axillary vessels pass around it.

Pectoralis minor - origin from ribs 3-5 to coracoid process of scapula

Origin: Anterior surfaces and upper margins of ribs III, IV, and V (as three muscular slips - numbered 1, 2, 3 in the diagram above)

Insertion: Medial and upper surface of the coracoid process of the scapula

Actions: Protracts the scapula (pulls it anteriorly); depresses the lateral angle of the scapula; assists in respiration

Innervation: Medial and lateral pectoral nerves (C8, T1)

Quick Position Summary

Muscle	Layer	Location	Key Landmark
Pectoralis major	Superficial	Entire anterior chest wall	Forms anterior axillary fold
Pectoralis minor	Deep (under major)	Ribs 3-5 to coracoid process	Divides the axilla into parts

Gray's Anatomy for Students, p. 844
THIEME Atlas of Anatomy - General Anatomy and Musculoskeletal System, p. 329-330

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