Muscles of Pectoral Region

Anterior Wall

Pectoralis Major

Muscle	Origin	Insertion	Nerve Supply	Action
Pectoralis Major	Clavicular head: §  Medial half of anterior border of clavicle §  Fibers pass downwards & laterally Sternocostal head: §  Half of anterior sternum §  upper 6 costal cartilage §  opponeurosis of external oblique	§  Bilaminar tendon into lateral lip of bicipital groove	§  Lateral pectoral nerves(C5, 6, 7) §  Medial pectoral nerves (C8, T1)	Both head: §  Adduct the arm & rotate it medially §  Muscle of respiration §  In climbing, draws body upwards Clavicular head: §  Flexion of the arm Sternocostal head: §  Extension of the arm

Pectoralis Minor

Muscle	Origin	Insertion	Nerve Supply	Action
Pectoralis Minor	§  3rd,  4th & 5th ribs, close to costalchondrial junction §  Fibers pass upwards & laterally	§  Medial border & upper surface of coracoids process	§  Medial pectoral nerve C8, T1	§  Draws the scapula downward & forward §  Depress shoulder §  If the shoulder is fixed, it elevates the ribs

Subclavius 

Muscle	Origin	Insertion	Nerve Supply	Action
Subclavius	§  upper surface of the 1st rib close to costal cartilage	§  Groove under surface of intermediate 3rd of clavicle	§  Nerve to subclavius C5, 6	§  Steady the clavicle in movement of shoulder girdle

Medial Wall

Seratus Anterior

Muscle	Origin	Insertion	Nerve Supply	Action
Seratus Anterior	§  8 fleshy digitations from corresponding outer surface of the upper 8 ribs §  1st digitations is from 1st & 2nd ribs	§  Ventral surface of superior & medial borders & inferior angle of scapula	§  Long thoracic nerve (nerve to seratus anterior) C5, 6, 7	§  Protect or pull the scapula forward §  Lower 5 digitations draw the lower angle of scapula forwards §  Raises the ribs in force inspiration