490 ABDOMEN 



and through the infero-lateral surfaces immediately below their 

 junction with the superior surface. When that has been done 

 the superior surface should be raised and the anterior border 

 and infero-lateral surfaces should be depressed ; a good view 

 of the interior will then be obtained. The mucous membrane 

 should be cleaned with a sponge and its general characters and 

 the orifices of the bladder should be studied. 



The Mucous Membrane, the Trigone, and the Orifices of 

 the Urinary Bladder. Over the greater part of the inner sur- 

 face of the empty bladder the mucous membrane is rugose, on 

 account of the laxity of its connection with the muscular 

 coat ; but in a triangular area on the lower part of the fundus, 

 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 that 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. Each infero-lateral surface 

 forms a part of the posterior wall of the cave of Retzius, and 

 it is separated by extra-peritoneal fat from the back of the 

 body of the pubic bone and from the fascia covering the 

 pelvic surfaces of the corresponding obturator internus and 

 levator ani muscle. The anterior border, which separates the 

 infero-lateral surfaces, lies behind the symphysis and above 

 the medial pubo-vesical ligaments. The neck of the bladder, 

 which lies at the meeting of the infero-lateral surfaces and the 

 lower angle of the fundus, is closely bound to the anterior 

 surface of the vagina, whilst in the male it is embraced by 

 the base of the prostate (see p. 443)- 



