Why does the human male reproductive system produce so many sperm cells?
1 Answer
In each ejaculate an adult male generally lodges at least 50 million sperms in vagina of female partner, but not more than 1 million will ultimately make it to the uterus. This is because some semen back flows, while acidic pH of vaginal wall kills some sperms, and many get trapped in mucus present near cervix.
Compared to microscopic sperm, which is one of the smallest cells of human body, uterus is a huge space. Only about 10,000 sperms successfully swim to reach the openings of oviduct at the top of the uterine cavity, but egg will be present inside only one of the oviducts. Thus many sperms lose the chance of meeting the eggs forever when they enter the wrong oviduct.
Ultimately, not more than a couple of hundred sperms, i.e. about 200 would be able to reach the location inside fallopian tube where the egg will be lodged. Inside fallopian tube sperms may take about two hours to swim the distance, during which most get exhausted and die.
So, more sperms definitely means better chances of fertilisation.
Sperms surrounding the egg will release hydrolysing enzymes to dissolve zona radiata and zona pellucida around the egg. Hence most of the sperms reaching an egg will be devastated to help one of their contestants to fertilise the egg cell.
