172 HUMAN ANATOMY. 



Auricula-ventricular opening, an oval aperture, rather 

 smaller than the right, and protected by the bicuspid or mitral 

 valve. 



THE EIGHT VENTRICLE. The right ventricle is triangular, 

 with thick walls (one-quarter inch), and occupies the anterior 

 part of the organ. Its capacity is about three fluid ounces. It 

 presents the following: 



Infundibulum, or conus arteriosus, a conical pouch, from 

 which the pulmonary artery arises; 



Columnce carnece, muscular columns projecting from the 

 inner surface, three or four of which (musculi papi flares) give 

 attachment to the chorda? tendineas; 



Chordce tendinece, delicate tendinous cords, connecting the 

 margins and central portions of the tricuspid valve with the 

 columns carneae; 



Tricuspid valve, consists of three triangular duplications of 

 endocardium, strengthened by fibrous tissue; they are attached 

 by their bases to the auriculo-ventricular orifice, and their free 

 margins give attachment to the chords tendineae; 



Semilunar valves, consist of three semicircular folds, guard- 

 ing the orifice of the pulmonary artery; their free margins are 

 thickened by nodules, the corpora Arantii; 



Opening of the pulmonary artery, at the apex of the conus 

 arteriosus, is circular in outline and protected by the semi- 

 lunar valves; 



Sinuses of Valsalva, three pouches, situated one behind each 

 semilunar valve. 



THE LEFT VENTRICLE. The left ventricle is longer, more 

 conical, and its walls three times as thick as the right. It 

 forms the apex and most of the posterior portion of the heart. 

 It presents the following parts in its interior: 



Columnce carnew, and 



Chords tendinece, much the same as the right; 



Auriculo-ventricular opening, a little smaller than the corre- 

 sponding orifice on the right side, similarly formed, and pro- 

 tected by the mitral valve ; 



The mitral valve consists of two unequal segments, attached 

 the same as the tricuspid, and also affording attachment to 

 the chordae tendineae; 



Aortic opening, a circular opening to the right of the 

 auriculo-ventricular opening ; 



The semi-lunar valves, three in number, surround the aorta, 

 and are larger and stronger than those on the right side; 



Sinus aortici (sinuses of Valsalva) are depressions situated 

 behind each valve. 



