Bones of the Upper Extremity. 



87 



Angulus medialis 



Acromion 



Facies articularis acromii Fossa subscapularis 

 Incisura scapulae \ Mar g superior 



Collum scapulae ' , 

 Cavitas glenoidalis ' 



Angulus lateralis ' 

 Tuberositas infraglenoidalis 



Margo axillaris 



Lineae 

 musculares 



Margo 

 vertebralis 



.Facies costalis 



Angulus inferior 



108. Right shoulder blade, scapula, from in front. 



The scapula (shoulder blade) (see also figures 109 112) is a broad, flat, thin, triangular 

 bone which lies upon the upper part of the wall of the thorax so that the lateral angle pro- 

 jects lateral ward over the thorax; its medial margin, 'when the arm is hanging down, runs 

 nearly parallel to the median plane and extends from the second or third to the seventh or 

 eighth, rib. It lies freely movable between the muscles and is connected by joints lateralward 

 with the clavicle and with the humerus only. 



The shoulder blade has three margins ; the thin, shortest, upper, margo superior, which 

 presents on its lateral extremity a notch, the incisura scapulae (0. T. suprascapular notch), 

 the longest, medial margin, margo vertebralis; the thick, lateral margin, margo axillaris. 

 These margins meet in three angles; the blunt, thick angulus inferior, the sharper, thinner 

 angulus medialis (0. T. superior angle) and the angulus lateralis (0. T. anterior angle); 

 the latter supports the surface for articulation with the humerus (see p. 89). 



The anterior surface, fades costalis, is markedly concave in its upper lateral part, 

 forming the fossa subscapularis; in other parts it looks smooth except for several ridges, 

 lineae musculares, directed toward the lateral angle, to which are attached tendinous bands 

 of the m. subscapularis. 



