The Ureter, Ureterovesical Junction, and Vesical Trigone.

The musculature of the ureter has a layered arrangement in which the internal layer is mainly longitudinal and the external layer is largely circular. There is, however, intermingling and migration of fascicles between layers. At the passage of the ureter through the bladder wall this layering is lost and all fascicles become oriented longitudinally. At the ureterovesical junction fibers of the detrusor muscle of the bladder, interspersed with delicate connective tissue, reflect onto the ureter over a distance to 2 to 3 cm. This “sheath” of the ureter, as it has been designated, is a reflection of bladder wall muscle onto the ureter. At its passage through the bladder wall, the ureter is loose and an injectable space exists around it. This is properly termed “Waldeyer’s separation” since he called attention to it in 1892. Within the bladder, the ureteric wall flattens and widens, allowing the lumen to migrate to the surface to constitute the ureteral aperture a t the angle of the vesical trigone. Delicate muscular decussations occur proximal and distal to the aperture. Ureteric muscle mainly forms the vesical trigone. Most fascicles run to the midline and blend with those of the opposite side in the interureteric fold. Others spread through the trigone, its lateral margin being formed of somewhat more numerous fascicles directed toward the vesical orifice. Very few fibers actually descend into the urethra. The principal fixation of the ureter into the bladder is to the mucous membrane of the trigone area and to the deeper lying muscle and connective tissue.