1284 THE UKO-GENITAL SYSTEM. 



behind, the urethral orifice the bundles of fibres are finer and more densely arranged, and 

 surround the opening in a plane which is directed obliquely downwards and forwards. 

 This part of the middle stratum is often spoken of as the " sphincter vesicse." Inferiorly 

 the fibres of the sphincter vesicse are continuous with the muscular tissue of the prostate 

 in the male, and with the muscular wall of the urethra in the female. In other parts of the 

 bladder the bundles of the middle stratum are coarser and separated by intervals filled with 

 connective tissue. The stratum internum is a thin layer of fibres directed for the most 

 part longitudinally. 



The tela submucosa or submucous coat is composed of areolar tissue, but contains 

 numerous fine elastic fibres. 



The tunica mucosa or mucous coat is loosely attached, by means of the submucous 

 layer, to the subjacent muscular coat, except in the region of the trigonum vesicae, where 

 the muscular fibres lie close beneath, and are firmly adherent to the mucous 

 membrane. Over the trigonum the mucous coat is always smooth and flat ; elsewhere it is 

 thrown into folds when the bladder is empty. The mucous membrane of the bladder is 

 continuous with that of the ureters and urethra. The epithelium, covering it, varies 

 much in appearance in different conditions of the organ, and is of the variety known as 

 transitional stratified epithelium. The appearance of the mucous coat is described 

 on p. 1277. 



Vessels and Nerves of the Bladder. The bladder receives its blood supply on each side 

 from the superior and inferior vesical arteries. The inferior vesical artery arises from the 

 hypogastric artery, and the superior vesical arises from the umbilical artery just before it becomes 

 obliterated. The largest veins are found just above the prostate, and in the region where the 

 ureter reaches the bladder. They form a dense plexus which pours its blood into tributaries of 

 the hypogastric vein, and communicates below with the pudendal venous plexus. 



The lymph-vessels from the bladder join the iliac group of lymph -glands. 



The nerve supply of the bladder is derived on each side from the vesical plexus, the fibres of 

 which come from two sources, namely (1) from the upper lumbar nerves through the hypogastric 

 plexus, and (2) from the third and fourth sacral nerves. The fibres from the latter sources join 

 the vesical plexus directly. 



THE URETHRA. 



The urethra is the channel which serves to convey the urine from the bladder 

 to the exterior. In the male it consists of two portions, a proximal part, less than 

 one inch in length, extending from the bladder to the points where the ducts of 

 the reproductive glands join the canal, and a much longer distal portion which 

 serves as a common passage for the secretion of the kidneys and for the generative 

 products. An account of the male urethra follows the description of the male 

 reproductive glands and passages (see p. 1304). In the female the urethra is more 

 simple in its arrangement, and represents only the proximal part of the male 

 canal. It is a short passage leading from the bladder to the external urethral 

 orifice an aperture placed within the rima pudendi or urino-genital cleft, imme- 

 diately above and in front of the opening of the vagina. 



Urethra Muliebris. The female urethra is a canal of about one to one and 

 a half inches in length which follows a slightly curved direction downwards and 

 forwards, below and behind the lower border of the symphysis pubis. As it 

 leaves the pelvis the urethra pierces the urogenital diaphragm and its fasciae, 

 and the part of the passage which lies between the superior and inferior layers 

 of fascia is surrounded by the fibres of the sphincter urethrse membranaceee 

 muscle. Except during the passage of fluid the canal is closed by the apposition 

 of its anterior and posterior walls. The orificium urethrae externum or external 

 orifice is placed between the labia minora, immediately in front of the opening 

 of the vagina, and lies about one inch below and behind the clitoris (Fig. 1002). 

 The opening is slit-like, and is bounded by slightly marked lateral lips. The 

 posterior wall of the urethra, except in its upper part, is very intimately connected 

 with the anterior wall of the vagina. The mucous lining of the canal is raised 

 into a number of slightly marked longitudinal folds, one of which, more distinct 

 than the others, and placed upon the posterior wall of the passage, receives the 

 name of crista urethralis. 



