While anal sex is commonly associated with male homosexuality , research shows that not all gay males engage in anal sex and that it is not uncommon in heterosexual relationships. Anal sex is considered a high-risk sexual practice because of the vulnerability of the anus and rectum. The anal and rectal tissues are delicate and do not provide lubrication like the vagina does , so they can easily tear and permit disease transmission, especially if a personal lubricant is not used. Strong views are often expressed about anal sex. It is controversial in various cultures, especially with regard to religious prohibitions.