Pronunciation (pek-to-RA-lis) Origin/Proximal Attachment Medial 1/3 of clavicle, anterior aspect of sternum, upper 6 costal cartilages, aponeurosis of external oblique Insertion/Distal Attachment Lateral lip of bicipital groove to the crest of the greater tubercle (clavicular fibres insert more distally, sternal fibres more proximally) Action/Relevance Adducts the armInternally rotates the armFlexes the arm (from an extended position) 4. Depresses the arm & shoulder Innervation Pectoral nerve - lateral (C5-7) to clavicular portion & medial (C8-T1) to sternal portion | 
