The tubes that carry excreted urine from the kidney to the bladder.
In humans, the ureters enter the bladder posteriorly. There are no valves in it, backflow being prevented by pressure from the filling of the bladder.
The ureter has three layers:
- a fibrous outer coat
- muscularis - inner longitudinal & outer circular layers of smooth muscle. Peristaltic waves keep the urine flowing
- mucosa - transitional epithelium with lamina propria; secretes mucous to protect lining