When it comes to making babies, the thought of sperm acting like bumbling drunks - blindly bouncing off uterus walls and each other - in order to be first to reach the egg may be humorous to many.
It also seems to be funny to researchers in the United Kingdom, who have studied the way these tiny cells negotiate their way through the female reproductive tract, an area that they have described as "potentially tortuous geometry", reported online journal Live Science.
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"I couldn't resist a laugh the first time I saw sperm cells persistently swerving on tight turns and crashing head-on into the opposite wall of a micro-channel," said lead study researcher Petr Denissenko of the University of Warwick in a statement.
To observe the sperm's behaviour more closely, a team of researchers led by the University of Warwick and University of Birmingham created an artificial environment designed to mimic the micro-channels found in the uterus.
Each micro-channel is approximately 100 micrometers wide (about the width of a human hair) and has different angles ranging from 90 degree corners to wavy bends to curvy, circular sections.
The researchers discovered it was the sharper bends that proved the most difficult for sperm to navigate, partly because of the viscidity, or stickiness, of the seminal fluid that helps carry them along.
"When the channel turns sharply, cells leave the corner, continuing ahead until hitting the opposite wall of the channel," the authors wrote.
Key questions the researchers asked were: "How are the millions of sperm selected down to around ten that reach the oocyte? And can we use a similar method to select sperm for fertility treatments?"
"In basic terms – how do we find the 'Usain Bolt' among the millions of sperm in an ejaculate," said lead study researcher Jackson Kirkman-Brown of the University of Birmingham in a statement.
"Through research like this we are learning how the good sperm navigate by sending them through mini-mazes."
The researchers hope that their findings will assist further research into fertility treatments and new in-vitro studies.
"Previous research from the group indicates that the shape of the sperm head can subtly affect how the sperm swim," concluded Kirkman-Brown.
"Combined with this data we believe new methods of selecting sperm, perhaps for quality or even in certain non-human species for sex, may become possible."
The paper Human sperm swimming in micro-channels was published May 7 in the journal Proceedings of the National Academy of Sciences.
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