140 



THE CIRCULATION OF THE BLOOD 



the blood is passing into it from the ventricle. When, 

 however, the ventricle is emptied and relaxes so that the 

 blood tends to return to it from the artery, they swell 



Right carotid artery 

 Thyroid gland (in front of larynx) 



Right vagus nerve 

 Vein from the thyroid gland 



Trachea 



Artery to right shoulder and arm 

 Vein from head, shoulder and 



Lett carotid artery 

 ;ft vagus nerve (to heart, 



stomach, etc- 



phrenic nerve (to diaphragm! 

 Thoracic duct 

 ry to left 



shoulder and arm 

 Vein from head 



shoulder and arnv 

 Pleura 



Left branch of pulmonary artery 



Tip of left auricle 

 Pulmonary artery 

 Left coronary artery 



Right ventricle 



Inferior vena cava 



FIG. 82. The heart and connecting blood-vessels. 



out with the backward movement of the blood and close 

 the opening. 



Arteries. Of these two large arteries, one, the aorta, 

 leads from the left ventricle, and its branches reach all 

 parts of the body. The other, the pulmonary artery, 

 leads from the right ventricle, and its branches reach all 

 parts of the lungs. Both the aorta and the pulmonary 

 artery are tough gristly tubes with highly elastic walls. 



