166 



ANATOMY FOR NURSES 



[Chap. X 



left auricle called the foramen ovale. Normally this closes as soon 

 as the infant })roathes. " • 



Valves of the heart. — The auriculo-ventricular orifices and the 



openings into the aorta 

 and pulmonary artery are 

 guarded by valves. 



The tricuspid valve. — 

 The valve guarding the 

 right auriculo-ventricular 

 opening is composed of 

 three irregular-shaped 



flaps, or cusps, and hence 

 is named tricuspid. The 

 flaps are mainly formed of 

 fibrous tissue covered by 

 endocardium. At their bases they are continuous with one an- 

 other, and form a ring-shaped membrane around the margin of 

 the auricular opening : their pointed ends are directed downward, 

 and are attached by cords, the chordae tendineae, to little muscu- 



FiG. 102. — Cross-sectiux thkough both 

 Ventricles, showing the Shape of their 

 Cavities and the Relative Thickness of 

 their Walls. (Gcrrish.) 



Fig. 103. — Valves of the Heart and Great Arteries, viewed from Above, 

 THE Auricles having been Removed. (Gerrish.) 



lar pillars, the papillary muscles, provided in the interior of the 

 ventricles for this purpose. 



The bicuspid valve. — The valve guarding the left auricular 

 opening consists of only two flaps or cusps, and is named the bi- 



