Art & Science


Fisting Anatomy

Systems and Components of the Fist Chute

Publication Details

Author: Finn Vortex

Published: 12/01/2015

Duration: 10 Minutes

Quick Links / Topics in this Article

Fist Chute: Lower Digestive System | Barriers: Skeletal System | Guts & Glory: Internal Organs | Pleasure Centers: Peripheral Nervous System

Executive Summary

Review of the anatomy of the fist chute with semi-technical explanations of the lower digestive tract, nervous system and skeletal structure. Basic notes provide details regarding fisting practices for each segment you encounter as you delve deeper into the chute. Also includes fisting jargon for specific anatomical features.

Fist Chute: Lower Digestive Tract

Knowledge of basic lower digestive tract helps Tops and Bottoms experience safer and more sensual fisting communion. In fisting circles, this area is referred to as the fist chute.

Navigable areas of the fist chute exclude part of the transverse colon and the ascending colon (in blue).
Understanding the
gross anatomyGross Anatomy (n)

the branch of anatomy that deals with the structure of organs and tissues that are visible to the naked eye
allows you to navigate through the obstacles and restrictions nature has in created inside our bowels. Lack of this knowledge while practicing advanced fisting (girth, punch, and depth) can result in injury or death.

The following components are discussed in this article:


The three component pieces of the anus: orifice, sphincter, and canal
Reference Notes
Length: 2 inches / 4-5 cm
Components: anal orifice, anal sphincter (first ring), anal canal
Related Jargon: hole, fuckhole, punchhole, mancunt, first ring

Anatomical Details and Roadmap

The anal orifice, the anal sphincter, and the anal canal are the three major components of the anus and are gatekeepers of the fist chute. The cell make-up of the anus gradually shifts from touch sensitive skin at the orifice (which provides most of the pleasure when fucking) to pressure sensitive intestinal tissue on far side of the anal sphincter (which provides most of the pleasure when fisting).

With anal sex, guys often talk about how tight a hole is based on the anal sphincter, which lies about an inch or so into the anal canal. Textbooks usually refer to two sphincters in the anal canal, but for fisting purposes, you may only feel one ring because the two sphincters are millimeters apart. It is important to note that inside a fist chute, individual anatomies can differ. In less established fisters, you may be able to feel both sphincters. This small distinction diminishes over time.

With some training, the Bottom can relax the ring on command to allow a fist to pass.

For the purposes of this website, both sphincters in the anal canal are referred to as the first ring.

    Fisting Notes Regarding the Anus

  • With the exception of
    prolapseProlapse (n)

    a condition where the rectum slips out of the body, exposing the dark red tissue of the lower GI tract
    , there are no documented cases or studies that state fisting causes incontinence later in life.
  • Massaging the orifice (including rimming) triggers a physiological response that opens the first ring and entry into the rectum.
  • Ask the Bottom how much 'first ring stimulation' he prefers prior to starting a session. Some holes need a lot of foreplay to open up; while other holes are agitated with prolonged play. Failing to ask can make the Bottom feel violated or bored—depending upon the needs of his hole.


The second ring is the demarcation point between the rectum and the sigmoid colon.
Reference Notes
Length: 5-12 inches / 10-30 cm
Components: rectum, puborectalis muscle (second ring)
Related Jargon: second ring, rosebud, garage

Anatomical Details and Roadmap

The opposite side of the first ring marks the beginning of the rectum, which can vary in size from person to person. In most people, the rectum is about 5-7 inches (13-18 cm) long. In extreme/established fisters, the rectum can be stretched to 12-15 inches (30-38 cm).

The rectal walls contain sensory nerves that monitor pressure and trigger physiological responses the adjoining components of the fist chute:

  • Relaxation of the first ring and muscles attached to anal canal (this response normally aids in defecation)
  • Relaxation of the second ring and reverse peristalsis (this response normally dissipates or pauses the need to defecate by retracting rectal contents back into the sigmoid)
Both of these responses trigger additional reactions in the body, including a cessation in breathing, an increase/decrease in blood pressure and heart rate, and the release of certain neurochemicals inside the brain. The combination of these responses result in a 'poop-euphoria' that many experience after a big (excuse the language) shit. This euphoria is also reproduced during fisting.

In experienced Bottoms, the rectum serves as a
resting pointResting Point (n)

a position inside a Bottom that does not trigger any expulsion response, thus allowing him to rest and recalibrate
. Basic and extreme fisting involve permanently stretching the rectum to accommodate an open hand or balled fist. Novice fisters experience a physiological sensation to push or expel the fist, while established fisters can keep a fist inside for extended periods of time.

The rectum is held in place by the puborectalis muscle that separates the colon from the rectum. This muscle is referred to as the second ring. This muscle typically lays near the top of the sacrum (see Fisting Anatomy: Sacrum) and marks the end of the rectum.

    Fisting Notes Regarding the Rectum

  • With novice Bottoms, the extra space inside the rectum allows a Top to curl his hand into a fist; however, further depth exploration usually requires the hand remain in the duck-billed position.
  • The prostate gland can be massaged through the rectum wall, increasing fisting pleasure in certain Bottoms. Tops should either ask directly OR monitor the body language of the Bottom to determine if prostate massage is pleasurable.
  • During a colonoscopy, physicians inflate the rectum and sigmiod with air; some men can do this through ingesting air through a gaping hole, or by pumping air into the rectum via a douche bulb or catheter. The expanded rectum becomes cavernous and easy to navigate. This state is often referred to as 'being really open'.

Sigmoid Colon

The actual 's' curves of the sigmoid are not well represented in anatomical drawings.
Reference Notes
Length: 16 inches / 40 cm
Components: pelvic and iliac colons
Related Jargon: s-curve

Anatomical Details and Roadmap

Passage into the sigmoid involves moving through the second ring, which is easily recognizable based on tissue density and elasticity. A related landmark that a Top may experience while passing into the sigmoid is the pelvic inlet (see Fisting Anatomy: Coxal); however, with many depth Bottoms the rectum stretches past/through this opening so that the entrance to the sigmoid is found deeper in the abdomen.

In some diagrams, the sigmoid is pictured as the pelvic and iliac colons, with an extensive set of curves (typically called the S curve) that rest in the concave portion of the pelvic bone. A Bottom can manipulate the S curve to straighten it with extensive toy play and repeated practice sessions with firmer toys.

    Fisting Notes Regarding the Sigmoid Colon

  • The second ring can be a hurdle to depth play if the Bottom is positioned incorrectly and the angle of entry is skewed. Many experienced Bottoms have preferred positions (sling, knees, or bed) that facilitate passing through the ring.
  • There are two anatomical configurations with depth fisting. The first involves a stretched rectum as noted previously—a Top can be elbow deep before he even reaches the sigmoid. The second involves entering the sigmoid with the full fist prior to reaching mid forearm—this allows for high bicep and pit depths.

Descending Colon

When the descending colon is fully traversed, the Top will be elbow-deep.
Reference Notes
Length: 10 inches / 22 cm
Components: descending colon
Related Jargon: none

Anatomical Details and Roadmap

If one makes it through the 16 inches (40 cm) of the sigmoid, it's a relatively straight shot through up the descending colon to the transverse colon. The descending is less elastic and narrower by design than other parts of the colon due to the nature of gravity pulling chyme from the transverse to the sigmoid.

    Fisting Notes Regarding the Descending Colon

  • Rapid movement at post elbow depths can present a danger to Bottoms; the Top should proceed with caution.
  • Passing into the upper sigmoid and descending colon may require the Top to reposition himself at awkward angles based on the Bottom's anatomy. Staying parallel with the fist chute is crucial—dropping the entry angle just a few milimeters can make the difference of several inches in depth.
  • It is incorrect to assume that all elbow-depth bottoms are experiencing a hand inside the descending colon. Remember the elasticity of the sigmoid and rectum allows them to swallow the entire arm.

Transverse Colon

The entire large intestine measures 5 feet—the Transverse is about 1/3 that length.
Reference Notes
Length: 18 inches / 46 cm
Components: Transverse colon, splenic flexure (third ring)
Related Jargon: third ring, grand ballroom

Anatomical Details and Roadmap

The last ring encountered in depth fisting is at the ninety degree angle between the descending and transverse colons. The technical name for this ring is the splenic flexure. Practice allows the transverse colon to straighten out, allowing the post elbow-depth arm to move past the stomach and towards the heart. The diaphragm will prevent a Top from directly touching the lungs or heart.

    Fisting Notes Regarding the Transverse Colon

  • To gain access, you may have to insert a finger into the splenic flexure and pull it down before inserting additional fingers and full fist.
  • Even though this area is sometimes referred to as the Grand Ballroom, movement should be gradual, slow, and graceful (with most Bottoms).

Barriers: Skeletal System

In addition to intimate knowledge of the lower digestive tract, understanding the skeletal components of the pelvis improves fisting pleasure.

Bottoms can feel sensitivity (pleasure or pain) as the hand/arm press against the bones of the pelvis.

In young adults under thirty years old, there multiple bones that compose and encapsulate the fist chute; however, by age 30, these bones fuse into the three distinct bones of the pelvis:

Bottoms that start fisting at a young age may have an advantage over their older counterparts. In young men, the pelvic bones are not fully formed nor locked into place until the late twenties. Fisting and toy play may help move, position, and mold the pelvis into a position that better facilitates fisting as they age. Fisters who started at an older age do not get the option to help the body design their fist chute portal.


The coccyx can vary in size from small (unnoticeable) to large (potential barrier)
Reference Notes
Length: 1-3 inches / 2.5-7 cm
Components: up to 5 coccygeal vertabrae
Related Jargon: tailbone

Anatomical Details and Roadmap

The coccyx, more commonly known as the tailbone, is composed of the last three to five vertabrae in the spine. Genetics, age, accidents, and fist chute modification (via repeated fisting) affect the size, position, and shape of the coccyx. For example, in younger adults, the vertabrae may not have fused into fewer segments.

Due to position and limited mobility, it can impede fisting, specifically entry into the rectum. In medium to large coccyx Bottoms, the coccyx may terminate at the base of the anal canal. Tops will be able to feel a solid wedge shaped bone as their hand enters into the rectum. In small coccyx Bottoms (or with Bottoms with broken tailbones), it may not even be detectible. This bone may shift back-and-forth like a light switch when pressure is applied.

    Fisting Notes Regarding the Coccyx

  • During the foreplay prior to fisting, use your fingers to try and locate the coccyx. If you can feel it, it is likely that you will have to enter the fist chute at a thirty or sixty degree angle so that your hand will glide past the wedge.
  • Large/medium coccyx Bottoms may have trouble girth fisting, as the opening to the fist chute can be limited by the coccyx.
  • If a Bottom knows he has a huge coccyx, he should instruct the Top on the best entry methods to ensure his anal canal doesn't get torn during a session.


The concave shape of the sacrum makes it a noticeable landmark within the fist chute.
Reference Notes
Dimensions: varies on gender, race, and size
Components: sacral vertabrae 1 - 5
Related Jargon: drive shaft, holy bone, strong bone

Anatomical Details and Roadmap

The coccyx is connected to the sacrum, which is another bone made up of fused vertabrae. The vertabrae begin fusing in the late teen years and terminate by age thirty. The back side of the sacrum is very bony, which can be felt when you rub hard at the top of your butt crack, down to the the opening of the fist chute.

The interior is smooth and concave. In some individuals, the curved nature is more prominent than in others. The curve can typically be felt as you pass through the second ring and feels like the stick shift in an manual transmission vehicle. Some Bottoms enjoy the sensation of a hand passing across the Sacrum, while others may experience intense pressure and limited pain as the hand passes over this ridge.

    Fisting Notes Regarding the Sacrum

  • If a Bottom is sensitive to pressure on the sacrum, pass over it with the palm down (when he is on his back), so that the knuckles do not scrape the bone. If palm down positioning is not possible, then lift or push palm toward the navel to prevent knuckle scraping. Alternatively, position the Bottom on his knees.
  • Once past the ridge, there are no pressure or pain points—find a spot that is comfortable for the Bottom to rest.


The pelvic aperture (opening) is the restrictive barrier for girth insertion.
Reference Notes
Dimensions: varies on gender, race, and size
Components: pubic symphysis, sacral joint, coxal bone
Related Jargon: Hip Bone

Anatomical Details and Roadmap

The coxal bones, also known as the hip bones, are a pair of bones locked in place by the sacrum and pubic symphysis (a small piece of cartildge). The bone is defined by three major parts, the ilium (the disk-like part), ischium (lower section), and pubis (pubic bone). These individual parts were fused into a single bone by age 15.

The three component pieces create the aperture (or opening), sometimes called the pelvic inlet. In men, this opening varies based on race and size, but the average diameter is about 4 inches (10 cm). The opening is apple shaped insted of circular so the limit on fist size is based on the narrowest point, which is often an inch less.

    Fisting Notes Regarding the Coxal

  • The inlet diameter can be increased by changing the position of the hips and legs. Some inlets expand when legs are closed in a squatting position, others apurtures expand when legs are opened or the hips are shifted up.
  • Gradual expansion of this opening is possible by repeated training with dildos or plugs. Advancement occurs at a snail's pace, usually only a few milimeters per year.

Guts & Glory: Internal Organs

The abdominal and pelvic cavities are home to a majority of our internal organs. Many of these organs will be temporarily dislocated while fisting at greater depths.

Organs of the Lesser Pelvis

The bladder and prostate receive stimulation during shallow fisting.

The Lesser Pelvis is often called the True Pelvis and contains the rectum, bladder, and prostate gland. These organs are all contained below the pelvic aperture and do not shift much during fisting.

Repeated stimulation of the prostate (by movement of the fist inside the rectum) increases the Bottom's pleasure, and pressing against the bladder can sometimes trigger urination (sometimes called piss fisting).

Organs of the Greater Pelvis & Abdomen


The Greater Pelvis, also called the False Pelvis, contains the remaining portion of the fist chute (sigmoid, descending, and transverse colon), as well as the kidneys. The liver, stomach, gall bladder, and spleen reside just above the Greater Pelvis in the abdominal cavitiy. These organs, with exception of the kidneys, may shift when the arm enters the upper fist chute. The barrier between the abdominopelvic cavity and the thoracic cavity is the diaphragm, which cannot be breached.

Peripheral Nervous System - Pleasure Centers

Additional content for this section is currently in development. Want to contribute?

I am not a medical doctor; however, I have had multiple thoracic and abdominal surgeries which provide greater insight into depth fisting. These surgeries involved a collapsed lung, an injury to the diaphragm and stomach, a perforation of the sigmoid, and laceration of the liver. Also included were laproscopic removal of the gall bladder and a traditional appendectomy.

One of these surgeries was fisting related while the other three were not; there are actual stitches inside my colon that allow me to gage where a Top is currently positioned inside my fist chute.