The seminal vesicles and the prostate provide most of the liquid in semen. The semen is deposited in the vagina and the sperm must then swim through the cervix into the uterus and up into the fallopian tubes. If an egg is present, it is fertilized in the fallopian tubes. The fertilized egg then moves down to the uterus, where it attaches to the wall and continues to grow. If no egg is present, the sperm may live within the uterus for up to 2 days.
Some reproductive hazards can stop or slow the actual production of sperm.
If the hazard prevents sperm from being made, sterility is permanent. Sperm Shape Reproductive hazards may cause the shape of sperm cells to be different. These sperm often have trouble swimming or lack the ability to fertilize the egg. Sperm Transfer Hazardous chemicals may collect in the epididymis, seminal vesicles, or prostate. These chemicals may kill the sperm, change the way in which they swim, or attach to the sperm and be carried to the egg or the unborn child.