A female is born with all the eggs she will ever have. While in the womb, a female fetus has about 6-7 million egg follicles. At birth, the number of follicles decreases to about 2 million and at puberty, the number falls to about 300,000. After puberty, a woman releases one mature egg every month during ovulation.
Under normal circumstances, sperm cells can only live for a few minutes outside a man's body.
For a man to be said to have a normal sperm count, his testicles need to produce more than 20 million sperm cells in one millilitre. The normal volume of semen in one ejaculate is about 1.5-5 millilitres. Hence, a man typically releases more than 40 million sperm cells in just one ejaculate. This means a man produces more than enough sperm cells to fertilise all the egg follicles a woman ever has in just one ejaculate.
Another interesting fact is that sperm cells are the smallest in the body while egg cells are the largest.