In the normal male reproductive tract, mature sperm are stored in the epididymides.
They travel through the vas deferns into the urethra, and exit the penis during ejaculation.
Vasectomy is a surgical contraceptive procedure whereby the vas deferens are permanently divided, preventing the spermatozoa from leaving the epididymis.
Following vasectomy, a man can only ejaculate seminal fluids that are free of sperm cells.