THE UKINARY BLADDEK. 1271 



large size. When the canal is empty the mucous coat is thrown into numerous 

 longitudinal folds, and so its lumen exhibits a stellate outline in transverse section. 

 The submucous tissue varies much in thickness in different parts of the ureter, 

 and contains some elastic fibres. The unstriated muscle fibres which compose the 

 tunica muscularis or muscular coat are collected into bundles which are separated by 

 a considerable amount of connective tissue, and are arranged, some longitudinally, 

 some circularly. In the upper part of the ureter a relatively large amount 

 of connective tissue is present deep to and among the bundles of muscle 

 fibres, which are arranged in three distinct strata an inner longitudinal, an 

 intermediate circular, and an outer longitudinal. In the middle part of the 

 vessel the same layers may be recognised, but the circularly disposed bundles of 

 fibres are more numerous than higher up. In the lower part of the ureter the 

 connective tissue is relatively scanty and the inner longitudinal fibres lie close to 

 the lining epithelium; in this region also the longitudinal folds of the mucous 

 coat become fewer and less marked. A short distance above the point where it 

 reaches the bladder, the wall of the ureter becomes much thickened by the 

 addition of a number of coarse bundles of longitudinally arranged muscle 

 fibres, which are applied to the outer surface of the muscular coat. These muscle 

 fibres form the so-called " sheath of the ureter," and are continued on the super- 

 ficial aspect of the vessel as it passes through the bladder wall. In the portion of 

 the ureter which traverses the wall of the bladder (pars intramuralis) nearly all 

 the fibres of the muscular coat are disposed longitudinally, i.e., in a direction 

 parallel to that of the vessel. The muscle fibres lie close beneath the epithelium, 

 and end just where the mucous coats of the bladder and ureter become continuous. 

 The tunica adventitia or outer fibrous coat of the ureter varies in thickness at 

 different levels, and in its lower part blends with the connective tissue which lies 

 among the muscle fibres forming the sheath of the ureter just mentioned. 



The mucous membrane of the calyces and of the pelvis of the kidney possesses an 

 epithelium resembling that of the ureter. Where each renal papilla projects into 

 one of the calyces a deep circular recess, or fornix, is formed between the wall of 

 the calyx and the sloping side of the papilla ; at the bottom of this recess the 

 epithelium of the calyx becomes continuous with that covering the papilla. At 

 the foramina papillaria the epithelium joins that of the kidney tubules. The 

 muscular fibres in the wall of the calyces and of the pelvis are collected into loosely 

 arranged bundles separated by wide intervals occupied by fibrous connective tissue. 

 As in the ureter, the outermost and innermost fibres run in a longitudinal, the 

 intermediate ones in a circular direction. The circularly arranged fibres alone 

 form a distinct layer. 



Vessels and Nerves of the Ureter. The abdominal part of the ureter receives 

 its blood-supply from the renal and internal spermatic arteries ; the pelvic portion 

 is supplied by the superior vesical and middle haemorrhoidal vessels. 



The nerves of the ureter reach it through the renal, the spermatic, and the 

 hypogastric, plexuses. 



Variations. The ureter is sometimes represented by two tubes in its upper portion. In rarer 

 cases it is double throughout the greater part of its extent, or even in its whole length from the 

 pelvis of the kidney to the bladder. In such cases there may be two openings into the bladder. 

 Asymmetry as regards such abnormalities is very common. 



Variations in the form of the pelvis of the kidney are of frequent occurrence. Most usually 

 the pelvis divides into two large subdivisions, one of which passes in the direction of the tipper, 

 the other in that of the lower pole of the kidney. In some cases these branches come off directly 

 from the ureter without the intervention of a pelvis, or a marked subdivision may lead to the 

 formation of two pelves. 



VESICA UEINAKIA. 



The vesica urinaria or urinary bladder is a hollow muscular organ situated in 

 the anterior part of the pelvic cavity, above and behind the symphysis pubis. It lies 

 in front of the rectum, from which it is separated in the male by the seminal vesicles 

 and the terminal portions of the ductus deferentes, and in the female by the vagina 

 and uterus. The ureters, which convey the fluid secreted by the kidneys, open into 

 the base of the bladder about half an inch from the median plane. 



81 G 



