When you purchase through contact on our site , we may earn an affiliate committal . Here ’s how it works .
Egg fertilisation is often described as an epic swim meet : Millions of sperm swim as fast as they can toward the orchis until one — the fastest , potent , healthy spermatozoon of them all — wins the race and wiggle into the egg , with the prize of give-up the ghost itsgenesto future progeny .
But is this really how it happens ? Do spermatozoan really rush to the testis ?
The concept of sperm “racing” toward an egg isn’t entirely accurate.
Yes and no , David J. Miller , a prof in the animal sciences section at the University of Illinois Urbana - Champaign , told Live Science . " The crucial player in all of this is actually the female reproductive tract . "
Sperm do swim during this process , but " the major movement is actually provided by contractions of the distaff tract , " Miller explain . " There are condensation of the womb , for example , that are much like contractions of the GI tract that can move fluid through the uterus . "
A1996 studyillustrated just how efficient these contractions are , Miller noted . scientist stick sperm cell - sizing beads into the uteruses of 64 women , and some of the beads trip all the way to the fallopian tubes — where fecundation usually takes topographic point — within hour .
The concept of sperm “racing” toward an egg isn’t entirely accurate.
Related : Are you genetically more standardised to your mom or your dad ?
It make sense that sperm would need some extra assist , because while the sperm drown in one direction , the egg needs to travel in the polar guidance to forgather them , Sabine Koelle , a full prof of physical body and developmental biology at the University College Dublin School of Medicine and Medical Sciences , differentiate Live Science . The eggs ca n’t drown , so instead tiny hair called cilia help it along .
" Cilia tick to transport the oocyte , " or egg , Koelle said . " Because the sperm are come from the diametric counsel , they have to struggle " against the current created by the cilia .
In fact , an individual sperm ’s movement is less of an movement to move ahead and more of an effort to moveinward , toward the heart of the tract , Koelle tell . If the sperm cell get too airless to the sides , they stick and lose their forward impulse .
However , just because a sperm is the first to arrive does n’t think it get to do the fertilizing . " Sperm require some last development that come about in the distaff pamphlet , and it ’s time dependent , " Miller said . " So the sperm that ' come through the race , ' so to verbalize , ask more time before they can actually fertilise the testicle . "
" They may not be there when they ’ve completed that maturation , " Miller added . " They might be replace by some of the other more slowly transport sperm cell that have had meter to complete that maturation . "
But even those less - fledged sperm cell are more successful than the vast legal age of sperm that get deposited . As the distaff reproductive tract push the spermatozoon along , it also cuts unlucky individuals from the swim team .
" Less than 1 % — perhaps up to 2 or 3 % of the sperm that are really deposited — make it all the way to where the ballock is , " Miller say . " A muckle of them are blush back out from the nerve tract . Some are eaten up by resistant cell in the womb , because sperm are strange . "
Up to 70 % of sperm do n’t even make it past the cervix , Koelle noted . " The sperm are stuck there and ca n’t release themselves , " she said .
For those few sperm that make it into the fallopian pipe , the goal is to get as far as potential and then stay to the wall as they wait for the bollock to come . This is another place where the female reproductive organs are choosing succeeder : scientist have noticed that normal - looking spermatozoan are more likely to bind to the wall , Miller said , and bind to the wall offer some metabolic benefits that increase their lifespan .
Then , once the ball arrives , the fallopian tube — also do it as the oviduct — allow only levelheaded - look spermatozoan to unstick from the paries . " As shortly as a spermatozoan is not hunky-dory , the Fallopian tube does n’t release it , " Koelle say . " It ’s the master selector switch of good spermatozoon . "
— Is the Y chromosome snuff it out ?
— How does DNA know which job to do in each cell ?
— What ’s the youngest geezerhood that a person can get pregnant and give giving birth ?
This is n’t a perfect system , of form . " Obviously , we have hereditary diseases that come through spermatozoan . So it ’s not always true that the fittest are the best one genetically , " Miller said .
Every footstep of the way , the female procreative nerve pathway is doing its good to weed out the less - fit sperm cell so that only goodish sperm cell make the eggs . In that way , fertilization is less like a race and more like a job consultation .
" There ’s certain qualifications that you ask to be able to apply for the job , " Miller enjoin . " But also , the sperm that have those qualifications would have to have them at the time the line is open — the sentence when the egg is ovulate . " But in the terminal , it ’s the female reproductive tract that chooses the best candidate .
You must confirm your public display name before commenting
Please logout and then login again , you will then be prompted to enter your display name .
Do animals have orgasms ?
Sex give ' microbic traces ' on genitals , even when a safe is used — scientist call it the ' sexome '
See the reconstructed home of ' frigid dinosaur ' that fly high in the Antarctic 120 million years ago
