I have long been fascinated with the idea of "upsuck" and was so pleased to see it discussed as part of the Discovery Channel's "Why Sex is Fun" show that I participated in. For those unfamiliar with the subject, upsuck is the term used to describe the contractions of the female reproductive system following orgasm that actually propels sperm toward an egg. Upsuck tends to indicate there is a biological reason for the female orgasm and that the female orgasm can help aid the process of getting pregnant. Not only is sperm "upsucked" it is directed toward the specific ovary that has released the egg that month increasing the chance of conception.
The following video demonstrates the process thanks to the help of some non toxic radioactive pseudo sperm and an injection of oxytocin to cause internal contractions mimicking orgasm. [youtube http://www.youtube.com/watch?v=xjYnG3iIZnY?wmode=transparent]