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APPLIED PHYSIOLOGY 



curtain fine threads extend to projections upon the muscu- 

 lar walls of the ventricle, to keep the curtains smooth and 

 straight. Blood flowing from the auricle into the ventricle 

 readily separates the curtains, but blood pressing upon 

 them from the ventricle forces them tightly together, so 



that not a drop can pass 

 through. Thus they form 

 a valve in each opening. 

 The valve upon the left 

 side is composed of two 

 curtains, and is called the 

 mitral valve. The one 

 on the right side is com- 

 posed of three curtains 

 and is called the trictispid 

 valve. From their situa- 

 tion, these valves are 

 often called the auriculo- 

 ventricular valves. 



285. Semilunar valve. 

 At the beginning of 

 each artery leading from 

 the ventricles are three 

 thin, silklike flaps, shaped 

 like half-moons. They 



are arranged so that blood flowing from the ventricle pushes 

 each flap against the side of the artery ; but between the 

 beats of the heart, the blood in the artery presses backward, 

 forcing the flaps away from the side of the artery, so that 

 they all meet tightly in the middle. They form a valve 

 called the semilunar valve, from the shape of each flap. 



286. Action of the heart. The heart is a pump with 

 valves permitting blood to flow through an auricle into a 



Systole of the heart. 



vein entering the auricle. 



b auricle. 



c closed valve to keep blood from flowing 



back into the auricle. 

 d ventricle. 

 e artery. 



