As a doctor, I can assure you that there is no magic protection in a woman's body to decide that some sperm are from a rapist and barred from the egg, while others are from a loving husband and have access. Akin's statement about this was just medically wrong. Check the CDC page, and the studies cited there.
"When more than one man has sex with a woman in a short period of time, she has within her sperm from different men. The goal of the sperm is to fertilize the egg. This is the reason for their existence. But when sperm from different partners are all placed in the same vagina, the sperm from each man groups together and does battle against the other groups of sperm. The winner gets to fertilize the egg."
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Now which sperm is going to win? The one that gets reinforcements nightly or the greatly out numbered sperm of the rapist?