Muscles of the Ann. 



29- 



342. Muscles of 



the right upper 



arm, 



viewed from the lateral 

 side. 



M. deltoideus (see also 

 Figs. 308, 310, 329, 330, 343, 

 347 and 349). Form: flat, 

 triangular, bent so as to be 

 markedly trougblike , thicker 

 in the middle than at the bor- 

 ders. Position: just beneath 

 the skin; it forms the fleshy 

 projection of the shoulder. 

 Origin: fleshy from the ex- 

 tremitas acromialis claviculae 

 and fhe acromion, tendinous 

 from the spina scapulae, connect- 

 ed with the fascia infraspinata. 

 Insertion: the anterior and 

 posterior fibers ruu in almost 

 straight line downward and 

 lateralward, the middle fibers 

 curve downward over the tuber- 

 culuni tnajus humeri (bursa 

 suhdeltoidca see Fig. 345) ; the 

 middle part of the muscle 

 presents a markedly pinnate 

 appearance ; all the fibers con- 

 verge to the tuberositas del- 

 toidea humeri, lateralward and 

 below the insertion of the m. 

 pectoralis major. Action: it 

 lifts the upper arm lateralward 

 in the shoulder joint. In- 

 nervation: n. axillaris. 



Bursa subcutauea acro- 

 mialis (see Fig. 349), often 

 present, just beneath the skin, 

 on the upper surface of the 

 acromion. 



Acromion 



Clayicula 



M. 

 deltoid 



W^ 



M. biceps 

 braciiii 



M. bracliialis 



Septum 



intermiisculare 



laterale 



(_)lecraiii)n 



M. 

 ancouaeus 



M. extensor 

 carpi ulnaris 



JI. extensor 

 digitorum 

 comnuiiiis 



-%- 



/i^ 



.\[. brachioradialis 



Epicondylus lateralis 

 humeri 



M. extensor jar 

 radialis lor 



M. extensor carpi 

 radialis brevis 



c* 



