CIRCULATION 



43 



Summing up the functions of blood, we may say that it 

 distributes nutrient materials and oxygen. It drains the tissues 

 of their waste, poisonous and useless materials. It serves as a 

 means of intimate connection between organs, e.g., as by con- 

 veyance of internal secretions produced by one organ and 

 needed as a necessary stimulant for the work of another organ. 



Fig. 23. — Circulation. Arteries Gray, Veins White. 



1, Heart, right ventricle; 2, left ventricle; 3, left auricle; 4, pulmonary 

 artery; 5, pulmonary veins; 6, anterior aorta; 7, carotid artery; 9, left 

 maxillary artery; 13, humeral artery; 14, radial artery; 15, metacarpal 

 artery; 16, digital artery; 17, posterior aorta; 18, coeliac trunk; 19, 

 mesenteric trunk; 20, renal (kidney) artery; 22, posterior vena cava (vein) ; 

 23, portal vein; 24, external iliac artery; 25, internal iliac artery; 27, 

 femoral artery; 28, posterior tibial artery; 29, metatarsal artery; 30, venous 

 supply to the foot; 33, jugular vein. 



It serves as a hot water heat circulating plant, carrying surplus 

 heat from actively working organs like voluntary muscles and 

 heart, where much heat is produced, and from internal organs 

 where heat loss is low, to skin and extremities, where the heat 

 loss is rapid. 



Circulatory apparatus. — Heart, arteries, veins, capillaries, 

 lymph spaces, lymphatic vessels, and lymph glands constitute 

 the circulatory apparatus. 



