PELVIS 633 



which is known as the trigone, the connection is closer and 

 the mucous membrane is always smooth. The rugae on 

 the other parts of the inner surface become unfolded as 

 the bladder distends, until the whole inner surface is 

 smooth. The trigone is also the most sensitive area of 

 the bladder wall. At its apex, which marks the lowest 

 point of the base of the bladder, is situated the semilunar 

 or Y-shaped internal orifice of the urethra, and at its lateral 

 angles, which are about one inch from each other and the 

 same distance from the orifice of the urethra, lie the slit-like 

 orifices of the ureters. The student should pass probes 

 into the ureters ; he will then be able to convince himself 

 that each ureter runs for about three-quarters of an inch in 

 the substance of the bladder wall, and that this part of 

 each duct can be easily palpated through the anterior wall 

 of the vagina. The obliquity of the ureters in the substance 

 of the bladder wall is believed to produce a valve-like action 

 of the lower parts of the ducts, permitting the passage of 

 urine into the bladder, but preventing its return. 



Relations of the Bladder. The relations of the infero- 

 lateral surfaces and the anterior border of the bladder are 

 practically the same in the female as in the male (see p. 587), 

 except that there is no prostate beneath the lower part of 

 the anterior border, and the neck of the bladder, which is 

 embraced by the prostate in the male, is closely bound to the 

 anterior wall of the vagina in the female. 



The superior surface which is in relation in the male 

 with coils of small intestine and pelvic colon, is overhung 

 posteriorly by the uterus in the female, and is in relation with 

 small intestine or a coil of the pelvic colon only in the 

 anterior part of its extent. The fundus of the bladder, which 

 in the male is in relation with the deferent ducts and 

 the seminal vesicles, is closely bound in the female to the 

 anterior surface of the neck of the uterus and to the upper 

 part of the anterior wall of the vagina (Fig. 244). 



Peritoneal Relations. The peritoneal relations of the 

 bladder are the same in the female as in the male (see p. 

 590), except that the upper part of the base may be covered 

 by peritoneum in the female. The alterations in the peri- 

 toneal relations which occur as the bladder distends are the 

 same in both sexes (see p. 588). 



Changes in the form of the Bladder. The changes which 



