THE RIGHT VENTRICLE 



531 



The axis of the cavity, taken from this ridge to the apex forms a spiral curve down- 

 ward and to the right. The septal wall is convex and faces obliquely forward 

 and to the right. 



The right atrio-ventricular orifice (Ostium venosum dextrum) is oval and is 

 situated opposite to the lower parts of the third and fourth ribs. It is guarded by 

 a tricuspid valve (Valvula tricuspidalis) ; of the three large cusps of this valve, one 

 is between the atrio-ventricular opening and the conus arteriosus, one is septal, 

 and the third is on the right margin. Small intei-mediate cusps intervene between 

 the large ones. The peripheral edges of the cusps are attached to the fibrous ring 

 at the atrio-ventricular opening. The central edges are irregular and hang down 



Anterior vena cara — 



Muscidus 

 peclmatus 



Rigid coronary 

 artery 



Tricuspid- -'\ 

 valve 



ChordcB' 

 tendineic 



Moderat 

 band 



Right V( 



Pulmonary 



artery Pulmonary 



^-'' veins 



^' '/ //I 



Great coronary 



vein 

 Left coronary 

 _ artery {cirout-fi- 



flex branch) 

 Bicuspid valve 

 Chordce tendinece 



Musculus papillaris 



Moderator band 



Right coronary artery ju^ 



— Left veritricle 



Fig. 423. — Section . ; 11 .■! of Horse. • 

 Specimen hardened in situ and cut nearly at right angles lo the ventricular septum. The left ventricle is contracted, 

 but not ad maximum. V. a.. Segment of aortic valve. 



into the ventricle; they give attachment to chordae tendinese. The auricular 

 surfaces are smooth. The ventricular surfaces are rough and furnish attachment 

 to interlacing branches of the chordae tendineae. The valves are folds of the endo- 

 cardium, strenglhened by fibrous tissue and at the periphery by muscular fibers 

 also. The chordae tendinese are attached below to the three musculi papillares, 

 Avhich project from the ventricular wall; superiorly they divide into branches 

 w^hich are inserted into the ventricular surfaces and the free edges of the valves. 

 Each segment of the valve receives chordae tendineae from two papillary muscles. 

 Of the latter, two are on the septum and the third and largest springs from the 

 anterior wall. 



The puhnonary orifice (Ostium arteriae pulmonalis) is circular and is situated 



