THE URINARY BLADDER 1367 



The vesical trigone or the trigonum vesicae (Fig. 1118) is a smooth, triangular 

 surface, with the apex directed forward, situated at the base of the bladder, imme- 

 diately behind the urethral orifice. It represents an equilateral triangle, the sides 

 measuring about one inch in the empty bladder and increasing to about one and 

 one-half inches in the distended bladder. It is paler in color than the rest of the 

 interior, and never presents any ruga?, even in the contracted condition of the organ, 

 owing to the intimate adhesion of its mucous membrane to the subjacent tissue. 

 It is bounded at each basal angle by the orifice of a ureter, and at its apex by the 

 orifice of the urethra. Projecting from the lower and anterior part of the bladder, 

 and reaching to the orifice of the urethra, is a slight elevation of mucous membrane, 

 particularly prominent in old persons, called the uvula vesicae. It is formed by 

 a thickening of the tunica propria. 



Stretching from one ureteral opening to the other is a smooth, slightly curved 

 ridge (torus interuretericus), the convexity of which is toward the urethra. It is 

 produced by transverse muscle fibres beneath the mucous membrane. The outer 

 prolongations of this ridge beyond the ureteral orifices are called the ureteral folds 

 (plicae uretericae). They are formed by the ureters as they traverse the bladder 

 wall. About the urethral orifice are slight radial folds of mucous membrane, 

 which are continuous with the longitudinal folds of the prostatic urethra. 



The internal urethral orifice (orificium urethrae internum) is sickle-shaped and 

 is surrounded by a circular prominence (annulus urethralis], which is most dis- 

 tinct in the male. 



Vessels and Nerves. The arteries (Fig. 473) supplying the bladder are the superior, 

 middle, and inferior vesical in the male, with additional branches from the uterine and vaginal 

 in the female. They are all derived from the anterior trunk of the interior iliac. The obturator 

 and sciatic arteries also supply small visceral branches to the bladder. The veins form a com- 

 plicated plexus around the neck, sides, and base of the bladder (Fig. 525). The veins communi- 

 cate below with the plexus about the prostate and terminate in the internal iliac vein. 



The lymphatics are few in number; they form two plexuses, one in the muscular and another 

 in the deep tissue of the mucous coat, and accompany the bloodvessels. The subepithelial portion 

 of the mucous membrane of the bladder contains no lymphatics whatever (Sappey). The mus- 

 cular tissue contains a few lymphatics. The subperitoneal tissues contain the usual number. 

 The collecting trunks from the anterior surface terminate in the external iliac nodes. The 

 trunks from the posterior surface terminate in the internal iliac nodes, The hypogastric nodes, 

 and the nodes in front of the sacral promontory. 



The nerves are derived from the pelvic plexus of the sympathetic and from the third and 

 fourth sacral nerves; the former supplying the upper part of the organ, the latter its base and 

 neck. According to F. Darwin, the sympathetic fibres have ganglia connected with them, which 

 send branches to the vessels and to the muscular coat. 



Surface Form. The surface form of the bladder varies with its degree of distention and 

 under other circumstances. In the young child it is represented by a conical figure, the apex 

 of which, even when the viscus is empty, is situated in the hypogastric region, about an inch 

 above the level of the symphysis pubis. In the adult, when the bladder is empty, its apex does 

 not reach above the level of the upper border of the symphysis pubis, and the whole organ is 

 situated in the pelvis; the neck, in the male, corresponding to a line drawn horizontally backward 

 through the symphysis a little below its middle. As the bladder becomes distended, it gradually 

 rises out of the pelvis into the abdomen, and forms a swelling in the hypogastric region, which is 

 perceptible to the hand as well as to percussion. In extreme distention it reaches into the umbili- 

 cal region. Under these circumstances the lower part of its anterior surface, for a distance of 

 about two inches above the symphysis pubis, is closely applied to the abdominal wall, without 

 the intervention of peritoneum, so that it can be tapped by an opening in the middle line just 

 above the symphysis pubis, without any fear of wounding the peritoneum. When the rectum 

 is distended, the prostatic portion of the urethra is elongated and the bladder lifted out of 

 the pelvis and the peritoneum pushed upward. Advantage is taken of this by some sur- 

 geons in performing the operation of suprapubic oystotomy. _ The rectum is distended by a 

 rubber bag, which is introduced into this cavity empty, and is then filled with ten or twelve 

 ounces of water. If, now, the bladder is injected with about half a pint of some antiseptic fluid 

 it will appear above the pubes plainly perceptible to the sight and touch. The peritoneum will 

 be pushed out of the way, and an incision three inches long may be made in the linea alba, 

 from the symphysis pubis upward, without any great risk of wounding the peritoneum. Other 



