Less than 5% of the ejaculate consists of sperm. Sperm cells, also
called spermatozoa or sperm, are made by the man's testes. Production of
sperm happens all the time, and it takes about 72 days for a man's body
to produce a fully formed sperm.
At the time of orgasm, the sperm get mixed with fluids made by the seminal vesicles and the prostate gland. This mixture is called the ejaculate or semen. In order to improve the chances of pregnancy, there have to be sufficient amount of sperm present in each ejaculation.