246 



ANATOMY AND PHYSIOLOGY 



(or cortical portion). The straight or collecting tubes are grouped 

 together into pyramids, pointing toward the interior and forming 



the medullary portion . The 

 apex of each pyramid pro- 

 jects into the sinus, pre- 

 senting the openings of sev- 

 eral collecting tubes (Fig. 



164). 



The cells which line 

 this system of tubes do the 

 work of excreting the urine 

 from substances in the 

 blood, thus relieving it of 

 poisonous elements which 

 would surely cause death 

 if allowed to remain. 



The urine is conducted 

 from the kidney to the blad- 

 der through the ureter, a 

 slender musculo-fibrous 

 duct about twelve inches 



long, the upper end of which is enlarged and called the pelvis of 



the kidney. (It occupies the sinus.) It has a thin layer of muscle 



fibers and is lined with mucous membrane. 



The two ureters extend into the true pelvis 



to the base of the bladder, where they 



terminate about one inch apart. 



The Urinary Bladder is the receptacle 



and reservoir for the urine and is situ- 

 ated in the pelvis just behind the pubic 



bones; between them and the rectum in 



the male pelvis, between them and the 



vagina and uterus in the female pelvis. 



It is a non-striated muscular sac, lined 



with mucous membrane which lies in ir- 

 regular folds when the sac is empty, but 



becomes smooth when it is filled. It has 



a covering of peritoneum above and posteriorly but not in front. 

 The upper portion of the bladder is the summit or vertex; the 



FIG. 163. SCHEME OF THE RENAL OR 

 MALPIGHIAN CORPUSCLE. 



i. Interlobular artery. 2. Afferent vessel. 

 3. Efferent vessel. 4. Outer wall. 5. Inner wall. 

 6. Glomerulus. 7. Neck of tubule. (Stohr.) 



FIG. 164. SECTION OF 

 KIDNEY. (Potter.} 



