SPLANCHNOLOGY 



The anterior angle of the trigonum vesicae is formed by the internal orifice of the 

 urethra: its postero-lateral angles by the orifices of the ureters. Stretching behind 

 the latter openings is a slightly curved ridge, the torus uretericus, forming the base 

 of the trigone and produced by an underlying bundle of non-striped muscular 

 fibers. The lateral parts of this ridge extend beyond the openings of the ureters, 

 and are named the plicae uretericae ; they are produced by the terminal portions of 

 the ureters as they traverse obliquely the bladder wall. When the bladder is 

 illuminated the torus uretericus appears as a pale band and forms an important 

 guide during the operation of introducing a catheter into the ureter. 



Vertex 



Int. urethral 

 orifice 



Uvulce vesicce 

 Trigonum 



Torus 

 uretericus 



Orifce of 

 ureter 





FIG. 1 140. The interior of bladder. 



The orifices of the ureters are placed at the postero-lateral angles of the trigonum 

 vesicae, and are usually slit-like in form. In the contracted bladder they are about 

 2.5 cm. apart and about the same distance from the internal urethra! orifice; in 

 the distended viscus these measurements may be increased to about 5 cm. 



The internal urethral orifice is placed at the apex of the trigonum vesicae, in the 

 most dependent part of the bladder, and is usually somewhat crescentic in form; 

 the mucous membrane immediately behind it presents a slight elevation, the 

 uvula vesicae, caused by the middle lobe of the prostate. 



Structure (Fig. 1141). The bladder is composed of the four coats: serous, muscular, sub- 

 mucous, and mucous coats. 



The serous coat (tunica serosa) is a partial one, and is derived from the peritoneum. It invests 

 the superior surface and the upper parts of the lateral surfaces, and is reflected from these on 

 to the abdominal and pelvic walls. 



The muscular coat (tunica muscularis) consists of three layers of unstriped muscular fibers: 

 an external layer, composed of fibers having for the most part a longitudinal arrangement; a 

 middle layer, in which the fibers are arranged, more or less, in a circular manner; and an internal 

 layer, in which the fibers have a general longitudinal arrangement. 



The fibers of the external layer arise from the posterior surface of the body of the pubis in both 

 sexes (musculi pubovesicales) , and in the male from the adjacent part of the prostate and its 



