MANUAL FOR STABLE SERGEANTS. 31 



The Urogenital System. 



68. The urinary organs are the kidneys, ureters, bladder, and 

 urethra. 



59. The kidneys are two glands situated one on either side of 

 the spinal column immediately below the lumbar vertebrae. Their 

 function is to separate waste material (urine) from the blood. 



6.0. The ureters are two fibrous tubes conveying the urine from 

 the kidneys to the bladder. 



61. The bladder is a muscular sac in which the urine is stored 

 until discharged from the body. 



62. The urethra is a mucous tube which extends from the^ 

 bladder to the head of the penis, in the male.^ In the female it 

 extends from the bladder to the floor of the vagina, about 3 inches 

 from the external opening. 



63. The urine is a yellowish fluid composed of water, various 

 salts, and waste materials from the body. The normal amount 

 secreted is from 3 to 6 quarts in 24 hours. The color and quantity 

 are variable, due to variations in food, work, and the temperature 

 of the air. 



64. The principal male generative organs are the testicles 

 and penis. 



65. The female generative organs are the ovaries, fallojnan 

 tubes, uterus, vagina, and vulva. 



The Circulatory System. 



66. The circulatory system consists of the heart, arteries, capil- 

 laries, veins, and the blood. 



67. The heart (fig. 16) is a hollow organ, made up of involun- 

 tary muscles. It is situated in the middle and left side of the 

 thoracic cavity, between the lungs, and is inclosed in a serous sac 

 called the pericardium. In shape it is a blunt cone with the base 

 upward and it weighs about 6| pounds. It is divided into two parts, 

 right and left, by a longitudinal muscular wall, or septum. Each 

 part is di\T.ded into two cavities, the atrium above and the ventricle 

 below. On each side the atrium and the ventricle communicate by 

 openings which are guarded by valves to prevent the back flow of 

 blood, but there is no communication between the two sides. The 

 function of the heart is to maintain the circulation by continually 

 pumping the blood through the arteries as it receives it from the veins. 



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