THE PELVIS 361 



The fascia transversalis is divided and the bladder is exposed 

 in the extra-peritoneal fat. The fingers are then passed upwards 

 until the line of peritoneal reflection is met, and the peritoneum 

 is then further elevated from the bladder., In order to prevent 

 the bladder from collapsing into the pelvis when it is incised, 

 two retention sutures are passed through its wall and are held 

 by an assistant during the operation. The bladder may now 

 be incised, and the calculus, tumour, etc., removed. 



The muscular coat of the bladder is very strongly 

 developed. Near the neck the outer fibres become continuous 

 with the muscular tissue of the prostate ; the intermediate 

 fibres are increased in number and form the sphincter vesicse 

 internus ; the inner layer becomes continuous with the 

 longitudinal muscular coat of the urethra. 



The mucous lining of the bladder is not so elastic as 

 the muscular coat, and is thrown into rugae when the bladder is 

 empty. This is permitted by the laxity of the submucosa ; but 

 over a triangular area which corresponds to the basal surface, 

 the mucous coat is smooth and firmly adherent to the muscular 

 wall. This area is referred to as the internal trigone : its superior 

 angles correspond to the openings of the ureters, and its inferior 

 angle to the internal orifice of the urethra, which is i\ inches 

 from the opening of either ureter. The ureters pierce the 

 bladder wall very obliquely, and when the intra-vesical pressure 

 is increased as the bladder fills, this arrangement provides a 

 valve -like action, which prevents a reverse flow towards the 

 kidneys. The ureteral openings are about two inches apart and 

 are connected by a ridge of mucous membrane called the inter- 

 ureteric bar. 



In hypertrophy of the muscular coat } to overcome the obstruction 

 caused by stricture of the urethra, prostatic enlargement, etc., 

 small pockets of mucous membrane may be formed in the 

 intervals between the bands of enlarged fibres. These loculi 

 sometimes form distinct diverticula, and they tend to retain 

 urine, which decomposes and gives rise to calculus formation. 

 The presence of incarcerated stones in the bladder wall can be 

 accounted for in this way. 



The Arteries of the bladder are derived from the hypogastric 

 (internal iliac) artery by means of three paired vessels, the 

 superior, middle, and inferior vesical arteries. 



Together with the ureter, lymphatics, and nerves, the 

 arteries and veins of each side are embedded in a sheet of visceral 



