Ureteral structure and ultrastructure. Part I. The normal human ureter

Twenty-eight normal human ureters were examined under the light and electron microscope. Three uretero-trigonal units were microdissected. The ureter is a non-layered muscular tube wherein the anatomical unit is muscle bundles that contain heterogeneously oriented muscle cells. Functional continuity of muscle cells is provided through the nexus, which are clearly defined structures. A group of morphologically distinct muscle cells are identified and these may represent the ureteral pacemaker cells. The functional status of muscle cells causes certain morphologic changes and, thus, the cells fixed in contraction differ from those fixed in relaxation and in vitro testing of muscle cell contractility is feasible. The ultrastructure of the normal urothelium and the adrenergic and cholinergic components of ureteral nerves are presented briefly.