<prompt> The narrowest pa of the ureter is at theUretero - pelvic junctionIlliac vessel crossingPelvic utererUretero - vesical junction  <response>: Ureterovesical junction is the anatomical position where the ureters join the urinary bladder. This is the narrowest of the ureter. Ureters are surrounded by the valves called as ureterovesical valve which will prevent the vesicoureteral reflux. Ref - urologyhealth.org 