When Sperm Met Egg

You might think that once the screaming is done and the load has been blown, the dance of the sexes is over. The highest quality male has sown his seed in the fertile female and all thats left is nine months of waiting. While the two of you are relaxing in the afterglow, the sperm are just beginning to fight their way to the egg.

Its only about three inches from the cervix to the fallopian tubes but a lot can go wrong in those three inches. It used to be thought that sperm just swim until they bump into the egg. It turns out to be more of a challenge than that. A challenge that requires the use of senses. It turns out that sperm have a sense of touch and smell.

In 2003, Israeli scientists found that human sperm are attracted to heat and that the area surrounding an egg is 2 degrees warmer than the rest of the uterus. It also seems that sperm stop swimming on their way to the egg to fully mature. The spot that they stop is cooler than the egg. After they mature, they are ready to fertilize.

To test the theory, the scientists built a lab with rabbit sperm at one end of a tube and a heat source at the other. They found that the sperm did travel towards the 102.2 degree F area, and away from the 98.6 degree F cooler area. Even changing the temperature by one half of a degree was enough to attract sperm. However, only the mature sperm went towards the egg. The previous theory had been that chemicals produced by the egg attracted sperm. But the chemicals only worked for a short distance, while heat traveled over a longer distance.

American and German scientists came to a different conclusion in that same year. They found a chemical scent similar to that of flowers attracted sperm to an egg. They found that sperm swim fastest when exposed to aromatic aldehyde bourgeonal, an artificial compound used in commercial products to give them a flowery smell. The aromatic aldehyde bourgeonal was chosen because it was closest to the odor in the female reproductive tract. Also, a protein odor receptor though to only be in the nose was found to be in testicular tissue.

While women have been said to have a better sense of smell than men, a Swedish team found that men are better at smelling the sperm attracting chemical, bourgeonal. A study from Psychological Science found that men found women to be most pleasant smelling when the women ovulated.

Scientists say that these findings could be used to create new forms of birth control.

Sources:
http://www.psychologytoday.com/blog/sensoria/201007/olfaction-and-conception
http://www.psychologicalscience.org/media/releases/2010/miller.cfm
http://www.sciencedaily.com/releases/2003/02/030203071703.htm