Found on the Internet. These people were promoters of anal sex for women, but nevertheless, I think they are onto something here:
For women, the clitoris has a large internal structure that can be stimulated either via the anus and anal sex or the vagina via vaginal sex. Women can have orgasms via vaginal sex through the G-spot. The G-spot is a way of stimulating the clitoris vaginally. There is also a G-spot in a woman’s anus. Via this method women can orgasm entirely from anal sex with no other stimulation, and even with other stimulation will have far more powerful orgasms than without anal.
A woman’s sexual pleasure does not come from her vagina; it comes from her clitoris. People often fail to realize this, because there are plenty of women who enjoy and get off from vaginal penetration without even touching their clitoris. Or so they think. There is far more to the clitoris than meets the eye. What you see is just the very tip of the iceberg. The rest of the clitoris consists of sensitive erectile tissue throughout the pelvic floor, part of which wraps around the vagina (called the corpus cavernosum clitoris), and another part of which extends back to the anus when erect (called the crura).
The vagina does not have many nerves at all because it is set up for babies to be able to pass through. However, the internal tissue of the clitoris that surrounds the vagina contains the nerves that are stimulated through vaginal penetration. These are the nerves that make sex pleasurable for a woman under the right circumstances. It is important to note that these nerves are not in the vagina, but merely stimulated through the vaginal wall. In many women, the nerves of this sensitive clitoral tissue can be stimulated just as effectively through the rectal wall during anal penetration.
Furthermore, anal penetration can make orgasms more intense for both men and women because the sphincters clench and unclench rapidly throughout an orgasm, and having something there for these muscles to clench on is how anal penetration intensifies an orgasm.
