THE BLADDER. 1003 



At the sides of the bladder the fibres are arranged obliquely and intersect one 

 another. This layer has been named the detrusor urines muscle. 



The middle circular layers are very thinly and irregularly scattered on the body 

 of the organ, and, though to some extent placed transversely to the long axis of the 

 bladder, are for the most part arranged obliquely. Toward the lower part of the 

 bladder, round the cervix and commencement of the urethra, they are disposed in 

 a thick circular layer, forming the sphincter vesicce, which is continuous with the 

 muscular fibres of the prostate gland. 



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 fibres, originating behind the orifices of the ureters, 

 converge to the back part of the prostate gland, and are inserted, by means of a 

 fibrous process, into the middle lobe of that organ. They are the muscles of the 

 ureters, described by Sir C. Bell, who supposed that during the contraction of the 

 bladder they served to retain the oblique direction of the ureters, and so prevent 

 the reflux of the urine into them. 



The submucous coat consists of a layer of areolar tissue connecting together the 

 muscular and mucous coats, and intimately united to the latter. 



The mucous coat is thin, smooth, and of a pale rose color. It is continuous above 

 through the ureters with the lining membrane of the uriniferous tubes, and below 

 with that of the urethra. It is connected loosely to the muscular coat by a layer 

 of areolar tissue, and is therefore thrown into folds or ruga? when the bladder is 

 empty. 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, a stratum of large club-shaped cells with the narrow extremity di- 

 rected downward arid wedged in between smaller spindle-shaped cells, containing 

 an oval nucleus (Figs. 560, 561). There are no true glands in the mucous mem- 



Fio. 560. Superficial layer of the epithelium of FiG.561. Deep layers of epithelium of bladder, 



the bladder. Composed of polyhedral cells of vari- showing large club-shaped cells above, and 



ous sizes, each with one, two, or three nuclei. smaller, more spindle-shaped cells below, each 



(Klein and Noble Smith.) with an oval nucleus. (Klein and Noble Smith.) 



brane of the bladder, though certain mucous follicles which exist, especially near 

 the neck of the bladder, have been regarded as such. 



Objects seen on the Inner Surface. Upon the inner surface of the bladder are 

 seen the orifices of the ureters, the trigone, and the commencement of the 

 urethra. 



The Orifices of the Ureters. These are situated at the base of the trigone, 

 being distant from each other about two inches ; they are about an inch and a half 

 from the base of the prostate and the commencement of the urethra. 



The trigonum vesicce, or trie/one vesical, is a triangular smooth surface, with 

 the apex directed forward, situated at the base of the bladder, immediately behind 

 the urethral orifice. It is paler in color than the rest of the interior, and never 

 presents any rugse, even in the collapsed condition of the organ, owing to the inti- 

 mate adhesion of its mucous membrane to the subjacent tissue. It is bounded at each 

 posterior angle by the orifice of the ureter, arid in front by the orifice of the urethra. 



