2.10.4. Pectoralis Major and Minor
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- Origin: Clavicle, sternum and 1st – 6th costal cartilages.
- Insertion: Lateral lip of bicipital groove of humerus.
- Nerve supply: Medial and lateral pectoral nerves (roots of C5, C6, C7, C8, T1).
- Action: Adducts arm and rotates it medially; the clavicular fibres of this muscle also flex the arm.
- Origin: 3rd, 4th and 5th ribs.
- Insertion: Coracoid process of scapula.
- Nerve supply: Medial pectoral nerve (root of C6, C7, C8).
- Action: depresses acromion of the scapula; however, if the scapula is fixed then the ribs of origin are elevated, so may have minor role in inspiration.
Pectoralis minor lies deep to (underneath) pectoralis major. Also, both muscles are actually present on both sides of the thorax, although this is not shown in the diagram.