Physiology. 



The Shape of the Heart. The heart is cone-shaped. 

 But the point or apex is down, and the big end, or base, 

 is up, so when we speak of the base of the heart we mean 

 the upper part, not the lower. 



The Position of the Heart. The base of the heart is 

 in the center of the chest, just back of the breastbone, 

 but the apex points downward and to the left (see Figs. 

 32 and 53). 



To Head and Arms 



Pre-caval Vein 



Right Auricle 



Pulmonary Artery 

 Left Auricle 



Left Ventricl* 



Apex 



Fig. 29. The Heart, from the front. 



The Size of the Heart. A person's heart is about the 

 size of his clenched hand. 



The Covering of the Heart. The heart is inclosed in a 

 loose-fitting bag, the pericardium. Within the pericardium 

 and around the heart is a small quantity of liquid, called 

 the pericardia I fluid. 



The External Features of the Heart. The larger part 

 of the heart is made up of ventricles, the auricles being 

 two ear-like flaps at the base, one on each side. There 

 is a deep notch between the auricles and the ventricles. 



