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VETERINARY PHYSIOLOGY 



In the right ventricle there are 1st. One or more small 

 horizontally running papillary muscles just under the pul- 

 monary orifice, their apices pointing backwards (fig. 109, 

 S.P.M.). 



2nd. A large papillary muscle taking origin from the mass 

 of fleshy columns at the apex of the ventricle (A.P.M.). 



3rd. One or more papillary muscles of varying size arising 

 from the posterior part of the apical portion of the ventricle 

 (P.P.M.). 



4:th. A number of small septal papillary muscles arising 

 from the septum. 



FIG. 109. The Right Ventricle and Ti icuspid Valve to show the relationship of 

 the Papillary Muscles and Chorda? Tendinese to the Cusps of the Valve. 

 (See text.) 



The distribution of the chordae from these muscles will be 

 considered in connection with the auriculo-ventricular valves. 



In contraction, the outmost and inmost layers of the 

 ventricles tend to approximate the apex to the base of the 

 ventricles, but this is resisted by the contracting middle layer. 

 The apex tends to be tilted towards the right, the papillary 

 muscles shorten, the columnse carneae by their shortening and 

 thickening encroach upon the ventricular cavity, and help 

 to abolish it, while the auriculo-ventricular rings are drawn 

 downwards and inwards towards the septum. 



