Basic Anal/Rectal Anatomy & Physiology

Anal sex play can be very pleasurable, if you prepare for it the right way. Unfortunately, a lot of people, women especially, have less than ideal experiences in their first anal encounters, largely from inadequate preparation (mental or physical). The result is often years of not wanting to try anything involving butt play again, which not only reduces a slut’s sexual skill set markedly, but also eliminates one major avenue of play that can dramatically increase the enjoyment and breadth of a total sexual experience.

As with any other sexual activity, the more you know and understand how the parts work, the easier it is to prepare for play involving those parts, and to enjoy that play. There are two primary pieces of the human anatomy involved in butt sex, the anus and the rectum.

Anatomy of the Anus

The Anus

The anus (butthole, asshole, shithole) is the hole surrounded by the wrinkled, rosebud looking muscle where feces exits and the various tongues, fingers, toys, penises, and other items you’ll use for pleasure will make contact and/or enter. The anus is surrounded by two sets of muscles that hold the opening closed. These muscles are known as sphincters, and are oriented such that it is much easier for objects inside to get out as opposed to allowing external objects to enter, which is an important point to understand as we discuss techniques for being sodomized.

There’s the external sphincter, which is a voluntary muscle – you can relax and tighten it up at will. Then there’s an internal sphincter. This muscle is involuntary and you typically have little control over it (though it is possible to train yourself to exert control over it). It exists primarily to keep you from shitting yourself. All kidding aside, it is designed to prevent unintentional emission of materials from your rectum. It has a little nerve embedded in it that can sense what’s trying to exit. So, if you’re needing to fart, for example, the muscle will allow you to relax it a bit so the air can be discharged. However, if it senses a solid material, it’s a different story; it will attempt to keep the material in until you relax the external sphincter. Sometimes, the material can be loose enough that it confuses the little nerve, however, and when you think you need to fart, you find yourself with quite the messy surprise. The ability to control the external sphincter becomes very important when the internal one decides it’s time to evacuate and you’re not in a position to accommodate that requirement.

One reason anal sex feels good to many people is the pleasurable sensations we get from having our assholes played with. That little ring of muscle has a great many nerves embedded in it, making it one of the most sensitive areas of the human body. Because it is so nerve-rich, however, it can also sense pain rather easily. So it is important to learn how to manage what’s going on back there if you wish to avoid painful anal penetration, or even if you are one of those who enjoys a bit of pain with your sodomy.

Another reason anal play can be rather intense is that the muscles involved in your orgasm, the pubococcygeus or PC muscles, are interconnected with those that make up the anus. PC muscles form the floor of the pelvis, and connect with many other minor muscles that work together during an orgasm. Thus, your anus also contracts and flexes when you have an orgasm. If you don’t believe that, insert your little finger into your anus and masturbate. You’ll feel it flexing as you get yourself off, and then when you do cum, you’ll easily feel the anus muscle tightening rhythmically as the climactic waves pulse through your abdominal and pelvic areas. When you’re being penetrated anally at the same time you’re having an O, your asshole will grab a hold of whatever’s in it and will help magnify the intensity of those contractions.

The key to allowing for painless anal insertion of toys and penises is learning how to relax the anus and get it used to having something inserted into it. Failure to learn this correctly can lead to anxiety and tensing up, which will lead to painful anal intercourse, thereby perpetuating the anxiety and making you less likely to “trust” the next time won’t hurt. That is why the first time you try it must be done after you’ve trained yourself.

Many people are surprised to learn that humans have anal glands, similar to other mammals. These glands are located in the tissue between the internal anal sphincter and the anal canal wall. They’re not shown on the diagram above. Most doctors and scientists believe these glands serve no purpose in humans. In other mammals, however, they produce scents used to identify members of the species to one another. Do the human glands produce a scent? No one knows for sure, but many people, regardless of their sex, are aroused by the musky scents associated with the anal area of another person.

One other quick note about the anatomy of this area. The anal canal itself is about one to one and a half inches long. When you examine the way butt plugs and other anal toys are designed (with a “neck” to them), you can understand why they are made the way they are.

Finally, you should note that anuses are the same in men and women. So regardless of who you’re playing with, everything in that area works identically on everyone you might encounter. There’s no need to adapt.

Anatomy of the Rectum

The Rectum

The rectum is the lower end of the digestive system, the tubular-shaped sack located behind the anus and extending back to the sigmoid colon. In most people, the rectum is between four and six inches deep. Its primary purpose is to serve as a holding chamber for feces just prior to its evacuation from your body. Under normal circumstances, the rectum is devoid of any significant material. When the lower colon releases feces into the rectum, it expands, triggering the feeling of needing to go to the bathroom. So long as you don’t feel this pressure, there should be no material inside, short of some minor amounts of stray fecal debris left over from earlier bowel movements.

When you sit down or squat down and relax your external sphincter, a signal is sent to a series of muscles in the rectum that create a peristaltic effect, thereby expelling the feces. This position also relaxes the 90-degree bend where the colon and the rectum join, thereby allowing material further up into the colon to pass into the rectum and out the anus as well (which is why what you expel is often much more than the 5-6 inches your rectum can typically accommodate). This process is often assisted through the purposeful contraction of the abdominal muscles to assist in the evacuation of the rectum. If you do not relieve yourself, the muscles in the rectum will eventually push the fecal matter back up into the lower colon until a later time. At some point, however, the amount of material is going to grow substantial enough that the pressure will become unbearable and you’ll have to go, or you’ll get constipated and will likely need some medicinal assistance in getting things cleared out.

The walls of the rectum are very vascular and hold a large number of blood vessels. This is why suppositories are an effective way of administering medications – the material dissolves and is directly absorbed into the blood stream. It is also why buttchugging (giving someone an alcohol enema) can be so dangerous, too. You’ll get drunk much, much quicker introducing alcohol into your body this way, vs. drinking it. And it is not uncommon for someone to get too much into their system in rather short order, resulting in alcohol poisoning. This vascularity also makes damage to the rectum much easier as well, and this can provide a robust route for the introduction of diseases. More on this in the next module.

The upper end of the rectum is attached to the sigmoid colon. The colon is closed off from the rectum itself by a kink, or 90-degree bend, until you squat to take a dump, at which time the pelvic floor sinks, allowing that bend to unkink and the contents to move downward. With some practice, if your rectum is not deep enough to accommodate a longer penis, toy, or other foreign object, you can allow these into your colon. Such deep penetration can be dangerous, however, and is not something recommended for beginners.

Finally, as with anuses, rectums are identical between men and women. The singular exception to this is that the rectum provides easier access to the prostate gland in men. In a later module, we’ll discuss prostate play when you’re with a man, and we’ll go over the details about how to find that little organ and use it to maximize a guy’s sexual pleasure.

So that’s the quick overview of how the parts work. Let’s now discuss some of the health and safety issues associated with anal play.