ANATOMICAL AND HISTOLOGICAL STUDY OF THE LOWER PART OF THE HUMAN URETER
Saber I. Shona, Mamdouh M.A. Rahman, Tarek A. Moneim and Rasha A. Radwan
Department of Anatomy, Faculty of Medicine, Cairo University
The antireflux mechanism permits one way flow of urine from the ureter to the bladder and prevents its return in the opposite direction. The nature of this mechanism is still not understood. In the present study, a trial was done to clarify this antireflux mechanism. The lower ends of both ureters, ureterovesical junction and the adjoining parts of the bladder of thirty adult cadavers were used in the present study. Gross anatomical examination was done for five adult specimens and histological examination (Hx & E and Masson's Trichrome stain) was done as well as image analysis for 25 specimens. Image analysis was done to detect the percentage and the ratio between the muscular and the connective tissue elements and their possible role in antireflux. The contour and the lumen of the lower end of the ureter were found to be variable not only in the different parts of the ureter, but also in the same part.It was found that the lower end of the ureter was surrounded by a sheath known as Waldeyer’s sheath which was fibromuscular in nature. It was almost purely fibrous in the juxtavesical part ,the muscular elements increase gradually towards the intravesical part. The orientation of the muscle fibers of the distal ureter varies from being three layers in the juxtavesical part, outer and inner longitudinal and a circular one in between, to become only longitudinal layers in the intravesical part.The musculature of the trigone of the bladder was found to be consisted of three superimposed layers, superficial which is the continuation of the ureter, middle which is the continuation of Waldeyer’s sheath and deep which is formed of the bladder musculature itself. Two bundles of bladder origin were detected: one was found to run transversely over the terminal part of the ureter near its orifice in the bladder and the other was found to be V-shaped divided into upper superficial and lower deep bundles surrounding the intravesical ureter in between. It was concluded that the antireflux mechanism is not a simple process but it is a complicated one depending on many factors including the oblique intramural ureter, the sheath around the ureter, the longitudinally arranged intravesical muscle fibers of the ureter in addition to both the transverse and the V-shaped vesical muscle bundles compressing the ureter and the compliance between the muscular and the connective tissue elements.