CHAPTER XIII 

 EXCRETION BY THE KIDNEYS 



Physiological anatomy of the kidneys Pyramidal substance Cortical substance Tubes of 

 the cortical substance Narrow tubes of Henle Distribution of bloodvessels in the kid- 

 ney Mechanism of the production and discharge of urine Influence of blood-pressure, 

 the nervous system etc., on the secretion of urine Physiological anatomy of the urinary 

 passages Mechanism of the discharge of urine Properties and composition of the urine 



Urea Origin of urea Influence of the ingesta on the composition of the urine and on 

 the discharge of nitrogen Influence of muscular exercise on the discharge of nitrogen 

 Uric acid and its compounds Hippuric acid, hippurates and lactates Calcium oxalate 



Xanthin, hypoxanthin, leucin, tyrosin and taurin Fatty matters Inorganic constitu- 

 ents of the urine Chlorides Sulphates Phosphates Water as a product of excretion 



Variations in the composition of the urine Variations with age and sex Influence 

 of mental exertion T Internal secretion Work of the kidneys. 



PHYSIOLOGICAL ANATOMY OF THE KIDNEYS 



THE kidneys are symmetrical organs, situated in the lumbar region, 

 beneath the peritoneum, invested with a proper fibrous coat, called the 

 capsule, and always surrounded with more or less adipose tissue. They 

 extend usually from the eleventh or twelfth rib downward to near the 

 crest of the ilium, and the right is always a little lower than the left. 

 In shape the kidney is appropriately compared to a bean; and the con- 

 cavity the deep, central portion of which is called the hilum looks 

 inward toward the spinal column. The weight of each kidney is four 

 to six ounces (113 to 170 grams), usually about half an ounce (14 grams) 

 less in the female than in the male. The left kidney is nearly always a 

 little heavier than the right. 



External to the proper coat of the kidney, is a certain quantity of 

 adipose tissue enclosed in a loose fibrous structure. This is sometimes 

 called the adipose capsule ; but the proper coat consists of a close net- 

 work of ordinary fibrous tissue, interlacing with small elastic fibres. 

 This coat is thin and smooth and may readily be removed from the 

 surface of the organ. At the hilum it is continued inward to line the 

 pelvis of the kidney, covering the calices and bloodvessels. 



The kidney in a vertical section presents a cavity at the hilum, 

 bounded internally by the dilated origin of the ureter. This is called 

 the pelvis. It is lined with a smooth membrane, which is simply a 

 continuation of the proper coat of the kidney and which forms little 

 cylinders, called calices, into which the apices of the pyramids are 



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