Anus and Rectum »

… sex toy or other means. However, since the anus was not constructed for penetration, but for excretion, this has to be helped by lubrication or damage to the wall or lining may occur. If you are being penetrated, it helps to relax the sphincter, to prevent pain or damage occurring through resistance.

Any unprotected oral or penetrative anal sex makes the person vulnerable to the numerous infections which are outlined in detail elsewhere on this site under the headings of HIV - …