122 



HUMAN PHYSIOLOGY 



CHAP. 



Carot/of 

 Arteries 



Pu/monary 

 'Artery 

 ertAt/r/c/e 



the surfaces and enables the heart to work with very 

 little friction. 



The heart is a hollow, muscular organ divided into 

 two separate parts, the right and left sides, by a strong 



partition which extends 

 from the base above to 

 the apex below. Each 

 side consists of two 

 chambers with an open- 

 ing between them. The 

 upper is called the auri- 

 cle, and the lower the 

 ventricle. The muscular 

 walls of the ventricles 

 are much thicker and 

 stronger than those of 

 the auricles, and those 

 of the left ventricle are 

 nearly three times as 

 thick as those of the 

 right. The reason for 

 this difference will ap- 

 pear when the functions of these chambers are described. 



Get a sheep's heart from your butcher and observe especially 

 the four chambers, the thickness of the walls, the valves, and the 

 openings. 



95. Valves and Openings of the Heart. The right 

 auricle has several openings through which the blood, 

 returned from all parts of the body, enters. The right 

 ventricle has one opening by which the blood enters 



FIG. 62. The heart and large blood 

 vessels, front view (Zuppke). 



