Fisting & Anatomy: the Anus…

After I posted part 1 1/2 about the anus and how flexible it is, I got a lot of questions if I can be more detailed. I will try, with the help of my doctor, some medical books, sex manuals and everything I could find on the internet resources.

The Anus
This is the anal canal’s external opening of soft, pinkish tissue folds, which give it a puckered appearance. The anus is located several centimetres below the tailbone and several centimetres above the scrotum, directly behind the perineum. The Anus is rich in blood and vessels and sensitive nerve endings that enjoy stimulation and touch. The area surrounding the opening is populated with follicles; while every adult has hair surrounding the anus, it varies in appearance from fine and downy to thick and dark.

The Anal Sphincters
The anal opening contains two sphincters. Although they’re called internal and external, they are actually somewhat overlapping bands of circular muscle.

The external sphincter is controlled by the central nervous system, which in turn controls all our voluntary muscles; suck those in our hands or legs. Typically, the external sphincter is under control; it’s the muscle you tighten when you want to go to the bathroom but you can’t go immediately.
The internal sphincter, by contrast, is part of the automatic nervous system, which controls reflexive functions such as breathing and blood pressure. With practice, one may learn exert some degree of influence over the action of the internal sphincter. This seems to be the spot that stores up much of the tension and stress in the anal region, which can lead to haemorrhoids and other anal discomfort.
A relaxed sphincter is capable of allowing feces to be expelled, whereas a tense sphincter is capable of excretion only by training, if at all. Likewise, it´s the tense state of the sphincters that makes anal penetration painful and difficult. Whereas relaxed sphincters facilitate pleasurable, pain-free anal penetration. Shortly we´ll explore some techniques for promoting anal relaxation.

The Perineal Muscles
Close to the sphincters are the perineal muscles, which have some relationship to the sphincters. The perineal muscles support the tissue surrounding the anus as well as the area between the genitals and the anus, called the perineum. My favourite spot…
Two specific perineal muscles are important to our purposes.

The first is the “bulbocavernosus” muscle.

In men, it envelops the bulb (not be confused with the head) of the penis, between the scrotum and the anus. This muscle serves to help empty the urethral canal after urination. After ejaculation, you can expel most residual seminal fluid by pressing firmly on the perineum, sliding you finger upward past the scrotum and along the underside of the shaft toward the urethral opening (meatus). You can feel the “bulbocavernosus” muscle by pressing on the approximate centre of your perineum. You may feel a slight twinge, and your penis may jump a little. Most men find some pressure on this point to be pleasurable, while others experience discomfort.

The second important muscle is the “pubococcygeus” muscle, more commonly known as the PC muscle.

This is the same one you use to stop the flow of urine while peeing. You can squeeze it while you´re urinating or by simply pretending to urinate. You can feel the muscle contract by placing your finger on your perineum (the area between your genitals and the anus). Also, you can felt the contractions strongly in your anus. The PC muscle contracts randomly during sexual arousal and rhythmically during orgasm. Learning to control it voluntarily can enhance the quality of sex.

To some degree, all orgasms are anal orgasms. The anal sphincters are connected to the pelvic floor running throughout the pelvis. The anus contracts at the muscles involved in orgasmic contractions.

The PC muscle is part of a flat, supportive muscle system known as the pelvic sling. The pelvic sling anchors to the pubic bone on one side, wraps behind the back of the rectum, and anchors to the other side of the pubic bone. It has two functions: to support the rectum, and to assist us in holding back a bowel movement. While the external sphincter has some influence over this, it’s mainly the job of the pelvic sling. It can become chronically tense, when it contracts, it compresses the rectum. This is possibly a major cause of constipation as well as not being able to enjoy anal penetration. Later we will explain how to get more relaxed and use these muscles in your comfort, which will enhance you anal pleasure.

The Rectum and the Anal Canal…
The rectum is about 20 to 22 centimetres long and opens directly into the anal canal, which is about 3 centimetres long. Because of their flexibility and strength, the anus and the rectum can adapt to a wide range of variously sized and shaped penises, butt plugs, and dildo´s.


A rich and complex network of nerve endings extends all around the anal opening, as well as underneath the head on the penis. Stimulation of these nerve endings is chiefly responsible for the pleasure (or pain) experienced during anal sex: However, the rectum, like the vaginal walls, responds more to pressure than other sensations. Thus, the anal walls are not as surface-sensitive as the anal opening.

Contrary to what everyone believes, the rectum isn´t a straight tube, in most people, it´s S-shaped, meaning that there are two major curves along its length. Running into the rectal wall with a sex toy penis or a fist accounts for much of the internal discomfort felt in anal sex.

Discomfort! Some people report feeling queasy or sore after being anally penetrated. Often, physical discomfort comes from not feeling completely relaxed at the time of intercourse: Most people find that prefer certain positions when being anally penetrated. It´s important that the penis, dildo´s or fist enters and moves at a comfortable angle, otherwise, it runs into the rectal wall, which can cause discomfort, even tearing or bleeding. Like I said before the rectum isn´t a straight tube and that its shape and elasticity vary from person to person. So be careful with insertion until you learn the location of the first rectal curve in your partner. Finger work before starting can help with this.

Farting happens during anal sex. For both parties this can be very uncomfortable, do not think the bottom is doing this on purpose! The best is to be matter-of-fact / cool about this. It´s nearly inevitable for the bottom to fart in some situations, basically, any time air has been pushed up to the butt when inserting toys, cocks or fists. This can happen during the enema. If you´re experiencing discomfort from trapped air, try breathing deeply. Laying on your side or in a position that your ass is higher than your head, crouching on all fours, you can push outwards on the exhalations.

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