STRUCTURE AND FUNCTIONS OF THE URETERS. 



membrane, passing over upon the base of the pyramids, while the muscle-fibers 

 cease at the foot of the pyramids, where they form a sort of sphincter about the 

 pyramids by means of circular bundles. The blood-vessels supply the various 

 layers and form a capillary network beneath the epithelium. The relatively 

 scanty medullated nerves, in the vicinity of which ganglia are found, in part 

 supply the muscles as motor fibers, while in part they penetrate toward the epithe- 

 lium. These are reflex and sensory, as indicated by the severe pain attending 

 impaction of calculi. The ureter penetrates the thickness of the bladder- wall, 

 passing obliquely through it for a considerable distance. The internal opening 

 is a slit in the mucous membrane directed obliquely inward and downward, and 

 provided with a sharp, valve-like process (Fig. 177) . 



The propulsion of the urine through the ureter takes place (i) in 

 consequence of the fact that the urine constantly secreted in the kidney 



under considerable 

 pressure forces on- 

 ward the urine in the 

 ureter, which is under 

 lower pressure. (2) In 

 the erect posture, the 

 urine flows by gravity 

 d own the ureter . ( 3 ) 

 The muscles of the 

 ureter through their 

 peristaltic movement 

 propel the urine into 

 the bladder. This 

 movement occurs on- 

 ly as a reflex phenom- 

 enon in response to 

 the entrance of the 

 urine, a few drops 

 every three-quarters 

 of a minute, or in con- 



FIG. 177. Lower Portion of the Male Bladder, with the Commencement of 



the Ureter, Opened through a Median Incision in the Anterior Wall, 

 and spread out (after Henle). The clear lines of the trigone, the slit- 

 like openings of the ureters, the ureters divided above and the seminal 

 vesicles can be recognized. On the colliculus seminalis there appear 

 in the middle the large opening of the prostatic sinus, and on either 

 side the small circular orifice of the ejaculatory duct, and below both 

 the numerous punctate openings of the excretory ducts of the prostate 

 gland. 



sequence of direct ir- 

 ritation. It always 

 passes downward 

 with a velocity of 

 from 20 to 30 mm. in 



a second. The greater the distention of the ureter by the urine, the 

 more rapidly does this peristaltic movement take place. Asphyxia, 

 venous hyperemia, and irritation of the splanchnic increase the number 

 of contractions; while rapid ligation of the renal vessels, as well as 

 ligation of the ureter, diminishes them. 



In case of local irritation, the contraction takes place in both directions. 

 As Engelmann observed these movements also in excised portions of ureter 

 in which neither nerve-fibers nor ganglia were visible, he believes that the move- 

 ments are due to direct muscular conduction in the unstriated muscles, just as 

 takes place in the heart. 



The stagnation of urine toward the kidney is prevented (i) by the 

 fact that the secretion collecting in the pelvis of the kidney and in the 

 calices under high pressure presses upon the pyramids from all sides, so 

 that the urine cannot pass back into the urinary tubules closed by pres- 

 sure. (2) If when the urine has accumulated in the ureter in consid- 

 erable amount, as from occlusion by concretions, the musculature en- 



