948 THE URINARY BLADDER. 



Interior of the Bladder. On opening the bladder, its internal surface is 

 found to be lined by a smooth membrane, which is so loosely attached to 

 the other coats, that in the flaccid condition of the organ it is nearly every- 

 where thrown into small wrinkles or folds, which disappear as soon as the 

 bladder is distended. Besides these, the interior of the bladder is often 

 marked by reticular elevations or ridges, corresponding with the fasciculi 

 of the muscular coat. 



At the lower and anterior part of the bladder is seen the orifice leading 

 into the urethra, round which the mucous membrane is corrugated longi- 

 tudinally. Immediately behind the urethral opening, at the anterior part 

 of the fund us, is a small smooth triangular surface, having its apex turned 

 forwards, which, owing to the firmer adhesion of the mucous membrane 

 to the subjacent tissues, never presents any rugse, even when the bladder 

 is empty. This surface is named the trigone (trigonum vesicse, Lieutaud) ; 

 at its posterior angles are the orifices of the two ureters, situated about 

 an inch and a half from each other, and nearly the same distance from the 

 anterior angle, where the bladder opens into the urethra (fig. 673). 



The orifices of the ureters, presenting the appearance of oval slits, are 

 directed obliquely forwards and inwards : they are united by a curved 

 elevation which extends generally outwards and backwards beyond them, 

 and which corresponds in position with a muscular band which joins them 

 together and to the neck of the bladder. Proceeding forwards from opposite 

 the middle of this, is another slight elevation of the mucous surface, named 

 the uvula vesicce (luette vesicale), which projects from below into the ure- 

 thral orifice. In the female, the trigone is small, and the uvula indis- 

 tinct. In the male, the uvula lies a little in advance of the middle lobe 

 of the prostate, and is sometimes prolonged on the floor of the prostatic 

 portion of the urethra. It is formed by a thickening of the submucous 

 tissue. In its natural state this may contribute to the more perfect closure 

 or apposition of the sides of the orifice of the bladder, and when enlarged 

 by disease it frequently produces serious obstruction at the commencement 

 of the urethra. 



Structure. The bladder is composed of a serous, a muscular, and a 

 mucous coat, united together by areolar tissue, and supplied with numerous 

 blood-vessels and nerves. 



The serous or peritoneal coat is a partial covering, investing only the 

 posterior and upper half of the bladder, and reflected from it upon the sur- 

 rounding parts in the manner already described in detail. 



The muscular coat consists of pale unstriped involuntary muscular fibres, 

 so arranged as to warrant the usual description of them as forming layers, 

 the outer of which consists of fibres more or less longitudinal, and the 

 next, of fibres more circular in disposition ; while, beneath this, is another 

 delicate longitudinal layer more recently recognised. 



The external or longitudinal fibres are most distinctly marked on the 

 anterior and posterior surfaces of the bladder. Commencing in front at the 

 neck of the organ, from the pubes in both sexes (musculi pubo-vesicales, 

 p. 265), and, in the male, from the adjoining part of the prostate gland, 

 they may be traced upwards along the anterior surface to the summit of the 

 bladder ; and they may likewise be followed down over the posterior 

 surface and base to the under part of the neck of the bladder, where they 

 become attached to the prostate in the male, and to the front of the vagina 

 in the female. Upon the sides of the bladder the superficial fasciculi run 

 more or less obliquely, and often intersect one another : in the male they 



