1144 THE URINARY ORGANS. 



of areolar tissue, excepting at the trigone, where its adhesion is more close. It is 

 provided with mucous follicles, more numerous than elsewhere near the neck of the 

 organ, but which are not regarded as definite glands. The epithelium covering 

 it is of the transitional stratified variety, consisting of a superficial layer of poly- 

 hedral, flattened cells, each with one, two, or three nuclei ; beneath these a 

 stratum of large club-shaped cells, with the narrow extremity directed downward 



FIG. 733. Superficial layer of the epithelium ol FIG. 734. Deep layers of epithelium of bladder 



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



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



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



and wedged in between smaller spindle-shaped cells, containing an oval nucleus 

 (Figs. 733, 734). 



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

 seen the orifices of the ureters, the trigone, and the orifice of the urethra. 



The Orifices of the Ureters. These are situated at each end of the base of the 

 trigone, being distant from each other by less than 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 (Lieutaud), or trigone vesicate, is a triangular smooth sur- 

 face, with the apex directed forward, situated in the base of the bladder immedi- 

 ately behind the urethral orifice. It is paler in color than the rest of the mucous 

 membrane, and never presents any rugae, even in the collapsed condition of the 

 organ, owing to its intimate adhesion to the subjacent tissue. It is bounded at 

 each posterior angle by the orifice of the ureter. Its antero-inferior angle is occu- 

 pied by the orifice of the urethra. Between the orifices of the ureters is seen an 

 arched fold (plica ureterica) of mucous membrane caused by the projection of 

 muscular fibres which have a similar direction (see preceding page). Projecting 

 from the lower and anterior part and reaching to the orifice of the urethra is a 

 slight elevation of mucous membrane called the uvula vesicce. It is formed by a 

 thickening of the submucous tissue. In the female, the uvula vesicae and trigonum 

 are small and ill-defined. 



The arteries supplying the bladder are the superior, middle, and inferior vesi- 

 cal in the male, with additional branches from the uterine and vaginal in the 

 female. They are all derived from the anterior trunk of the internal iliac. 

 The obturator and sciatic arteries also supply small visceral branches to the 

 bladder. 



The veins form a complicated plexus round the neck, sides, and base of the 

 bladder, and terminate in the internal iliac vein. 



The lymphatics accompany the blood-vessels, passing through the glands sur- 

 rounding them. 



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

 the third and the fourth sacral nerves ; the former supplying the upper part of 

 the organ, the latter its base and neck. According to F. Darwin, the sympa- 

 thetic fibres have ganglia connected with them, which send branches to the ves- 

 sels and muscular coat. 



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

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



