The urethra is a part of the renal system, which also includes the kidneys, ureters, and the bladder. The female urethra starts at the base of the bladder and continues down through the pelvic floor.

Smooth muscle differentiation is induced in the embryonic bladder by the centrally located urothelium in the undifferentiated mesenchyme in the periphery adjacent to the serosa. We hypothesize that ...