hippie4lyfe saidOkay it sounded fancy. You often hear the argument that anal sex is unnatural, that the anus is an outhole and therefore should not be used for penetration.
What about the vagina though? Is it not an outhole as well? Pee comes out of there, so forget the natural argument for a minute where obviously nature designed it so in order to procreate you gotta enter that muff palace, but aren't you technically penetrating an outhole?
Pee isn't pathogenic waste like feces and it serves a positive function for the vagina/penis.
When you have sex the semen/whatever-fluid-girls-have neutralize the acidity in their respective organs, else the sperm would have no chance of reaching the egg. The function urine provides is, usually a few minutes after sex, to raise the acidity of the respective sex organs in order to prevent disease from taking hold. This is why a woman's vagina is much more resistant to HIV taking hold than that same woman's anus.
So while pee comes from both your penis and a females vagina it serves a purpose besides removing harmful waste from the body.
The OTHER outhole, common to both men and women, serves an entirely different purpose. That purpose is to safely remove harmful pathogens and other waste from the body. When an anus is used for sex male or female, two things can happen depending upon who the does what.
The intestines function by absorbing nutrients from food as it passes through your digestive tract. When you practice receptive anal sex you run the risk of your intestines absorbing (and rather easily) your partners sexual fluids, especially if you have anal sex without a condom. This function increases the risk of becoming infected by an STI or HIV a very real possibility, if not a certainty if your partner has a disease.
The other role, toping, is much more safe but the danger concerning this role goes along with the function of the penis. As you have sex the semen in produced by your penis neutralizes the acidity within your penis, allowing for the safe transfer of sperm. But the problem arises at orgasm. Since the anus is almost always under positive pressure, having an orgasm inside your partners anus involves a kind of trade off. For every spurt of sperm you give the positive pressure of the anus pushes pathogenic waste into the urethra, eliminating any chance of avoiding disease by allowing pathogens to take hold while the acidity is gone.
That's quite a few cents by me