Risk of STI infection, however, is generally considered significantly lower for oral sex than for vaginal or anal sex, with HIV transmission considered the lowest risk with regard to oral sex. The term is less common today. Bukkake and gokkun may also involve oral sex. Because of the aforementioned factors, medical sources advise the use of condoms or other effective barrier methods when performing or receiving oral sex with a partner whose STI status is unknown. Terminology and slang There are many words which refer to oral sex, including euphemisms and sexual slang. A play on the slang term head resulted in the slang term brains, or brain salad surgery, domes or getting domes. Oral sex can also be performed by both partners at the same time in the so-called "sixty-nine" position. Plate — A once common British rhyming slang for fellate that arose in the gay slang language of Polari that spread in the s. Autofellatio is a possible but rare variant; autocunnilingus may also be possible for women with extremely flexible spines. Additionally, in lesbian culture, several common slang terms used are carpet munching, giving lip, lip service or tipping the velvet a faux-"Victorian" expression invented by novelist Sarah Waters. While some headlines have interpreted this as evidence that oral sex among teenagers is "on the rise", this was the first comprehensive study of its kind to examine the matter. In humans, there is no connection between the gastrointestinal system and the reproductive system , [nb 1] and sperm ingested by the woman would be killed and broken down by acids in her stomach and proteins in the small intestine. The study found that 36 percent of the cancer patients had HPV compared to only 1 percent of the healthy control group. This is apparent in the two Latin words for the act: The study concludes that people who had one to five oral sex partners in their lifetime had approximately a doubled risk of throat cancer compared with those who never engaged in this activity and those with more than five oral sex partners had a percent increased risk. Plastic wrap may also be used as a barrier during oral sex, but there exists no conclusive scientific research regarding how effective it may or may not be at preventing disease transmission. Under this system, it was considered to be abhorrent for a male to perform fellatio, since that would mean that he was penetrated controlled , whereas receiving fellatio from a woman or another man of lower social status such as a slave or debtor was not humiliating.