Each time an egg is fertilized, only one sperm is successfully fertilized, which means that tens or hundreds of millions of other sperm are useless. So why does the success of egg fertilization depend on sperm count rather than sperm motility?
The reason is that the sperm that successfully unites with the egg is generally not the strongest sperm, but the “luckiest” sperm.
It is the “luckiest” sperm.
Let’s look at the sperm’s journey through life and death.
First, the sperm is wrapped in semen (seminal plasma) and ejected. Imagine thousands of people sliding down a super high slide at a water park, which would surely lead to a stampede!
Although the sperm is tougher than the living some, at least will not fracture anything (although the ding can fracture), but, during this period will also happen a series of accidents. For example ……
The sperm’s tail is torn off – death!
Sperm is shot outside – dead!
The tails of several sperm entwined – everyone hugged death!
This death does not have anything to do with strength, sperm can not resist the flood of semen even if they are strong!
Well, even if the sperm good character, to avoid the stampede, that there is a second level. You know, a woman’s immune cells are free to enter and leave the vagina (this is also the basic principle of sexual transmission of AIDS), and in the “eyes” of these immune cells, there are only two things in the world.
Their own cells and other things that must die.
Well, sperm is something else ……
The vagina is a warm, moist, dark and not very clean place, it’s a breeding ground for bacteria, and if we don’t get tough on immunity, humans will become extinct.
It’s okay, sperm swim fast (really fast, I’m not going to tell you that I chased sperm all over the field of vision when I did the single sperm injection ……), you can run if you can’t beat them. That’s true, but ……
Sperm are blind!
So in reality, the sperm is just swimming around in the vagina, and if you are lucky, you might just run towards the cervix, and if you are unlucky, you might just turn around a few times and let the white blood cells click.
So the vagina is a slaughterhouse! It’s worse than paper towels, eh.
Of course, even if the success of the escape, if the escape when too much wrong way also can not, because the sperm storage energy is relatively limited, and …… wrong way to go too much then too much behind, even if the persistence to the end of the point is not much. This story tells us that there is no future for roadkill ……
Well, if the sperm character really good to burst, did not go too much wrong way through the cervix, into the uterus, sperm luck finally to be a little better, because the human uterus is very small, not with too much effort to pass, if replaced by the rat’s uterus, it will have to die a large.
The reason why the human womb is so small is because humans generally give birth to only one at a time, so it can fit a fetus inside, while rats can give birth to twenty to thirty at a time ……
However, after the uterus and will die half of the sperm, because although humans do not have two uterus, but there are two fallopian tubes, even women themselves do not know which fallopian tube the egg in which, so the sperm to go which way, only by …… guess!
Because of the fallopian tube there is no turning back to go (there is no point in turning back ……), so this level will kill a bunch of bad character as well as a phobia of choice (fog) of sperm.
When you get to the fallopian tube, you finally get to the egg (the ones that died in the fallopian tube are not mentioned), and the sperm have to usher in their big boss, the egg! That’s right, the egg!
Because outside the egg there is a layer of extremely dense structure called the zona pellucida (in fact, outside the zona pellucida there are egg mound cells, but that little barrier can basically be ignored, at most can kill 70% to 80% of the sperm, basically negligible ~)
The zona pellucida is a bug that exists in general, why say so? Because the sperm can use their own “head” (technical term called the acrosome) to dissolve the zona pellucida, dissolve a hole in the zona pellucida for sperm to pass through.
It takes many, many sperm “working together” to dissolve the zona pellucida, and as soon as one sperm passes through the zona pellucida, the zona pellucida quickly locks up, preventing other sperm from entering.
So the last sperm to unite with the egg is not necessarily the strongest, but the one that is in the right place at the right time when the zona pellucida is about to dissolve!
The majority of sperm die because they are not strong, so in the long evolution, the sperm, or males have to use the sea of people, ah no, the sea of sperm tactics ~.