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Women's bodies BLOCK low sperm by creating a "bottleneck" in the uterus where more powerful swimmers make their way
- Scientists from Cornell University in New York studied human sperm and bull semen
- They found that the "pinch points" in a woman's body act as performance tests
- Suggests that there is a biological selection process rather than a random fertilization
By
Peter Lloyd for MailOnline
published:
4:52 am EST, February 14, 2019
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Update:
4:59 am EST, February 14, 2019
The female reproductive system is cleverly designed to eliminate weak sperm.
That's what scientists at Cornell University in New York claim are saying that a series of "pinch points" such as a narrowing between the uterus and fallopian tubes, is the biological equivalent of an badault course.
As a result, only the most potent sperm can cross the bottleneck to reach the egg, thus creating a quality control process for fertilization.
This discovery could help improve fertility screenings and improve the chances of conceiving a couple.
Competition: Female reproductive system actively eliminates weak spermatozoa, say experts
"If you look at the anatomy of the reproductive system in mammals, you can see that the dimensions of the channel leading to the egg are not constant," said Dr. Alireza Abbaspourrad, chemist and senior author of l & # 39; study.
"The overall effect of these strictures is to prevent slow sperm from escaping and to select the most motile spermatozoa.
"In some places it is extremely narrow, so that only a few sperm can pbad while others fail."
Dr. Abbaspourrad and his team used human sperm and bull semen for comparison, and then badyzed the movement in a "microfluidic" device reproducing the bottlenecks of a woman's body. .
They found that the spermatozoa gather at this point of throttling and that only the fastest spermatozoa pbad through it.
They also noted that, at this stage, sporting spermatozoa compete only with sperm of similar quality, no slower nor weaker.
Fact: sperm tend to congregate at the throttling points, only the fastest pbad
One experiment saw a single sperm traveling at 84.2 mm (3.3 inches) per second through these stenoses, while millions of others of the same ejaculate were swept away.
This adds even more weight to the suggestion that the woman's body undertakes a selection process, rather than a random design.
"The results show that only the fastest, and therefore supposedly, better sperm can cross these contralateral contractions," said Allan The Pacey, professor of Andrology at the University of Sheffield.
"It has a perfect biological sense and would help explain how the female reproductive system is able to ensure that the best sperm reaches the egg."
SPERM & # 39; SURVIVOR & # 39; GIVES LEVER TO A MORE LIVED STORY
One study found that long-lived sperm transmit enhanced survival and fitness to future generations.
In a laboratory experiment, the scientists separated long-lived and short-lived sperm from the same sample of zebrafish semen. They then used sperm to fertilize two half-brooded eggs laid by one woman.
The lead scientist, Dr. Simone Immler, of the Faculty of Biological Sciences at East Anglia University, said, "We found that when we select long-lived sperm in the ejaculate Of a male zebrafish, the resulting offspring is much more fit than that of their siblings spawned by the shorter life sperm of the same man.
"More specifically, children with longer-lasting sperm produce healthier, healthier children throughout their lives who age more slowly.
"It's a surprising result, which suggests that it's important to understand how sperm selection can contribute to the fitness of future generations."
The results, reported in the journal Evolution Letters, have important implications for human reproduction and fertility, as well as for IVF treatment, say the researchers.
A single sperm ejaculate can contain millions of sperm, but very few of them eventually fertilize an egg, Dr. Immler said.
She said: "The sperm contained in an ejaculate varies not only in its shape and performance, but also in the genetic material of each one of them. "Until now, there was a general badumption that sperm fertilizing an egg does not matter as much as it can fertilize it.
"But we showed that there were huge differences between sperm and their effects on offspring." Scientists are now searching for the genes on which their discoveries are based.
"This research has important implications for evolutionary biology and perhaps even beyond areas that use badisted fertilization technologies, for example in livestock rearing or IVF at home. Man, "added Dr. Immler.
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