THE MUSCULAR SYSTEM 69 



MUSCLES OF THE UPPER EXTREMITY 



MUSCLES OF THE SHOULDER AND ARM 



Pectoralis major. Teres major. 



Pectoralis minor. Teres minor. 



Subclavius. Coracobrachialis. 



Serratus magnus. Biceps flexor cubiti. 



Deltoid. Brachialis anticus. 



Subscapularis. Triceps extensor cubiti. 



Supraspinatus. Subanconeus. 



The pectoralis major muscle is located upon the chest. * 

 Origin, from the clavicle, sternum, and upper six costal 

 cartilages. Insertion, into the humerus. Action, draws 

 arm downward and forward. 



Pectoralis Minor. Origin, from the third, fourth, and ^ 

 fifth ribs. Insertion, into the coracoid process of the scap- 

 ula. Action, depresses the shoulder and assists in the 

 elevation of the ribs during the act of inspiration. 



The subclavius arises from the first costal cartilage and ^ 

 rib, and is inserted into the inner surface of the clavicle. 

 Action, draws the clavicle downward. 



The serratus magnus arises by nine fleshy digitations 

 from the outer surface of the eight upper ribs ; it is inserted 

 into the posterior border of the scapula, Action, elevates 

 ribs in inspiration ; fixes scapula in act of pushing. 



The deltoid is a thick, triangular muscle forming the 

 convexity of the shoulder. Origin, from the upper border 

 of the clavicle, outer and upper surfaces of the acromion 

 process, and lower border of the scapula. Insertion, into 

 the outer side of the humerus. Action, raises the arm to 

 a right angle, and draws it forward or backward. 



The subscapularis arises from the inner two-thirds of the 

 subscapular fossa; is inserted into lesser tuberosity of the 

 humerus. Action, rotates the humerus inward as well as 

 adducts the same. Nerve, subscapular. 



