170 PHYSIOLOGY FOR DENTAL STUDENTS. 



say that the cardiac cycle is completed in about one-tenth of a 

 second. Systole of the auricles takes about one-tenth of a second, 

 systole of the ventricle three-tenths of a second, and diastole 

 about four-tenths of a second. 



Diseases of Cardiac Valves. If the mitral valve is diseased, 

 the blood may be retarded from flowing from the auricle into the 

 ventricle. This condition is called mitral stenosis. If the valves 

 cannot close tightly and thereby permit the blood to regurgitate 

 into the auricle during ventricular systole, the condition is called 

 mitral insufficiency. Disease of the semilunar valves is likewise 

 divided into aortic stenosis and insufficiency, depending on the 

 character of the functional change in the valves. 



