THE URINARY BLADDER 



1233 



Transitional 

 epithelium 



Submucous coat 



Inner layer of 

 longitudinal 

 "muscle fibers 



! Circular muscle 

 fibers 



Outer layer of 

 longitudinal 

 muscle fibers 



Fro. 1141. Vertical section of bladder wall. 



capsule. They pass, in a more or less longitudinal manner, up the inferior surface of the bladder, 

 over its vertex, and then descend along its fundus to become attached to the prostate in the 

 male, and to the front of the vagina in the female. At the sides of the bladder the fibers are 

 arranged obliquely and intersect one another. This 

 layer has been named the Detrusor urinae muscle. 



The fibers of the middle circular layer are very 

 thinly and irregularly scattered on the body of the 

 organ, and, although to some extent placed trans- 

 versely to the long axis of the bladder, are for the 

 most part arranged obliquely. Toward the lower 

 part of the bladder, around the internal urethral 

 orifice, they are disposed in a thick circular layer, 

 forming the Sphincter vesicae, which is continuous 

 with the muscular fibers of the prostate. 



The internal longitudinal layer is thin, and its 

 fasciculi have a reticular arrangement, but with a 

 tendency to assume for the most part a longitudinal 

 direction. Two bands of oblique fibers, originating 

 behind the orifices of the ureters, converge to the 

 back part of the prostate, and are inserted by means 

 of a fibrous process, into the middle lobe of that 

 organ. They are the muscles of the ureters, de- 

 scribed by Sir C. Bell, who supposed that during 

 the contraction of the bladder they serve to retain 

 the oblique direction of the ureters, and so prevent 

 the reflux of the urine into them. 



The submucous coat (tola submucosa) consists of 

 a layer of areolar tissue, connecting together the 

 muscular and mucous coats, and intimately united 

 to the latter. 



The mucous coat (tunica mucosa) is thin, smooth, and of a pale rose color. It is continuous 

 above through the ureters with the lining membrane of the renal tubules, and below with that 

 of the urethra. The loose texture of the submucous layer allows the mucous coat to be thrown 

 into folds or rugce when the bladder is empty. Over the trigonum vesicse the mucous mem- 

 brane is closely attached to the muscular coat, and is not thrown into folds, but is smooth and 

 flat. The epithelium covering it is of the transitional variety, consisting of a superficial layer 

 of polyhedral flattened cells, each with one, two, or three nuclei; beneath these is a stratum 

 of large club-shaped cells, with their narrow extremities directed downward and wedged in 

 between smaller spindle-shaped cells, containing oval nuclei (Fig. 1141). The epithelium varies 

 according as the bladder is distended or contracted. In the former condition the superficial cells 

 are flattened and those of the other layers are shortened; in the latter they present the appear- 

 ance described above. There are no true glands in the mucous membrane of the bladder, though 

 certain mucous follicles which exist, especially near the neck of the bladder, have been regarded 

 as such. 



Vessels and Nerves. The arteries supplying the bladder are the superior, middle, and inferior 

 vesical, derived from the anterior trunk of the hypogastric. The obturator and inferior gluteal 

 arteries also supply small visceral branches to the bladder, and in the female additional branches 

 are derived from the uterine and vaginal arteries. 



The veins form a complicated plexus on the inferior surface, and fundus near the prostate, and 

 end in the hypogastric veins. 



The lymphatics are described on page 712. 



The nerves of the bladder are (1) fine medullated fibers from the third and fourth sacral nerves, 

 and (2) non-medullated fibers from the hypogastric plexus. They are connected with ganglia 

 in the outer and submucous coats and are finally distributed, all as non-medullated fibers, to the 

 muscular layer and epithelial lining of the viscus. 



Abnormalities. A defect of development, in which the bladder is implicated, is known 

 under the name of extroversion of the bladder. In this condition the lower part of the abdominal 

 wall and the anterior wall of the bladder are wanting, so that the fundus of the bladder presents 

 on the abdominal surface, and is pushed forward by the pressure of the viscera within the abdomen, 

 forming a red vascular tumor on which the openings of the ureters are visible. The penis, except 

 the glans, is rudimentary and is cleft on its dorsal surface, exposing the floor of the urethra, a 

 condition known as epispadias. The pelvic bones are also arrested in development. 



