VEINS 151 



the duodenum, small intestine, and ascending and transverse 

 colons. 



The Inferior Mesenteric artery arises a short distance above 

 the bifurcation of the aorta. It passes downwards over the left 

 psoas and becomes the superior haemorrhoidal. It supplies the 

 descending colon and the rectum. 



f 



The Veins. 



The veins are formed by the aggregation of the capillaries, 

 and return the blood to the heart. They,, like the arteries, are 

 arranged in two sets pulmonary and systemic. The pulmonary 

 veins enter the left auricle of the heart by four openings, and 

 the systemic veins i.e., the coronary sinus, and superior and 

 inferior venae cavae enter the right auricle by three openings. 



The Pulmonary veins are found in the alveoli of the lungs, 

 and form a single large vessel for each lobe. In the root of 

 the right lung the veins from the upper, and middle lobes join 

 together,, so that two veins pass out from the root of each 

 lung to enter the left auricle. 



Systemic Veins. The systemic veins, three in number, all 

 enter the right auricle. 



The coronary sinus returns the blood from the walls of the 

 heart only. The superior vena cava returns the blood from the 

 head, neck, upper limbs, thoracic wall, and a part of the pos- 

 terior abdominal wall. The inferior vena cava returns blood 

 from the lower limbs, and the walls and organs of the abdomen 

 and pelvis. 



The veins of the body wall and limbs are arranged in two 

 sets superficial and deep. The superficial veins run in the 

 superficial fascia, and the deep veins accompany the arteries, 

 usually as venae comites. The superficial veins ultimately pierce 

 the deep fascia to unite with the deep veins. The visceral veins, 

 of which there is usually one accompanying the artery, end 

 in the deep systemic veins, with the exception of the portal 

 vein. 



The Coronary Sinus lies between the left auricle and left 

 ventricle, and terminates in the lower and back part of the 



