530 



ANGIOLOGY 



I 



The inferior vena cava, larger than the superior, returns the blood from the 

 lower half of the body, and opens into the lowest part of the atrium, near the 

 atrial septum, its orifice being directed upward and backward, and guarded by 

 a rudimentary valve, the valve of the inferior vena cava (Eustachian valve}. The 

 blood entering the atrium through the superior vena cava is directed downward 

 and forward, i. e., toward the atrioventricular orifice, while that entering through 

 the inferior vena cava is directed upward and backward, toward the atrial septum. 

 This is the normal direction of the two currents in fetal life. 



The coronary sinus opens into the atrium, between the orifice of the inferior 

 vena cava and the atrioventricular opening. It returns blood from the substance 

 of the heart and is protected by a semicircular valve, the valve of the coronary 

 sinus (valve of Thebesius}. 



Pulmonary valve 



Opening of sup. vena 



cava 



Crisia terminalis 

 Atrial septum 



Limbus fossce ovalis 



Opening of coronary 

 sinus 



Opening of inf. vena 

 cava 



Ant. ciisp of tricuspid 



valve 

 ; Chordce tendinece 



Papillary 

 muscles 





Valve of inf. vena cava 



Valve of coronary sinus 



FIG. 493. Interior of right side of heart. 



The foramina venarum minimarum (foramina Thebesii) are the orifices of minute 

 veins (vence cordis minima), which return blood directly from the muscular sub- 

 stance of the heart. 



The atrioventricular opening (tricuspid orifice) is the large oval aperture of com- 

 munication between the atrium and the ventricle; it will be described with the 

 right ventricle. 



The valve of the inferior vena cava (valvula vence cavoe infcrioris [Eustachii]; 

 Eustachian valve) is situated in front of the orifice of the inferior vena cava. It 

 is semilunar in form, its convex margin being attached to the anterior margin 

 of the orifice; its concave margin, which is free, ends in two cornua, of which 

 the left is continuous with the anterior edge of the limbus fossae ovalis while 

 the right is lost on the wall of the atrium. The valve is formed by a duplicature 

 of the lining membrane of the atrium, containing a few muscular fibers. In the 

 fetus this valve is of large size, and serves to direct the blood from the inferior 

 vena cava, through the foramen ovale, into the left atrium. In the adult it occa- 

 sionally persists, and may assist in preventing the reflux of blood into the inferior 

 vena cava; more commonly it is small, and may present a cribriform or filamentous 

 appearance; sometimes it is altogether wanting. 



