Role of ureter: Ureters occurs in pairs and are part of the human excretory system. It connects the kidney to the urinary bladder and carries urine from the kidney to the urinary bladder. (It is not a part of the reproductive system).
Role of urethra: In the male reproductive system the urethra functions in both the reproductive and excretory system. In the excretory system it function to carry the urine from the urinary bladder out of the body. In the reproductive system the urethra functions in the ejaculation of semen. When the penis is erect, the flow of urine is blocked in the urethra and only semen can pass.