Muscular layer of ureter

The ureter is composed of three coats: adventice (fibrous coat), muscular coat, and mucous coat.

In the renal pelvis the muscular coat (tunica muscularis) consists of two layers, longitudinal and circular: the longitudinal fibers become lost upon the sides of the papillæ at the extremities of the calyces; the circular fibers may be traced surrounding the medullary substance in the same situation. In the ureter proper the muscular fibers are very distinct, and are arranged in three layers: an external longitudinal, a middle circular, and an internal, less distinct than the other two, but having a general longitudinal direction. According to Kölliker this internal layer is found only in the neighborhood of the bladder.