.....Knowing about the anatomy of the nether regions is a very good idea if you want to poke things up there without causing big problems—but anatomy can be complicated.
.....Of course, for our purposes, we’re most interested in the doorstep & door, entry hall, first chamber, and then the rest of the magic tunnel with all its twists & turns—kinda like a Hobbit Hole.

The Main Door: Yeranus
	The perianal region—the sensitive area around the anus—is supposed to have more nerve endings per square whatever than the head of a dick (and I believe ‘em). It’s the most erotic zone on my body for sure. A great place to play around before knockin’ on the door and making a grand entrance. Like faces, no two anus are exactly alike and that makes for wonderful variety.

Entry Hallway Evil Guards: Your Sphincters
	.....The guards at the door are two rings of muscle that overlap a bit called the internal and external sphincters. The external one is at our beck and call (closest to the outside), but the internal guard ignores our brain requests (at first), and that’s why so many guys have a problem getting in the house that first time. That internal door literally has a mind of its own. .....Now both these muscle rings guard the first chamber—rectum—and go through a floor of muscle at the bottom
of our pelvis called the levator ani. That base wall of muscle comes into play in fisting too, so we need to know how to tease it as well to have the most fun (more on that later).

The Ballroom: Your Rectum
	.....The ball room is where the dances all begin. Your rectum is where dumps are stored before you deposit them where you will. It’s a sack with muscular walls that can contract to help push things out the door, and you can feel pressure there that will blow your ever-lovin’ mind (just insert 5 pounds of cold chain and you’ll know what I mean). Some fisters never venture beyond this room—and love it.

Doorway to Heaven: The Sigmoid
	.....The sigmoid valve must be negotiated to get high depth. This guard-door has a narrow opening that helps keep shit up in the descending colon before the rectum is ready for it—in other words, it helps keep us from dirtying our trousers before we’re ready to… This puppy IS at our command (like the external sphincter, who dances in tandem with it), so between learning to talk nicely to it and stretching it, you can really guarantee your ability to
take ‘em deep! (See training.)

The Last Guard: Sergeant Puborectalis
.....Another muscle hanging around the outer area is the puborectalis. Its a slingshot of muscle that attaches the front of the pubis, and then wraps around the base of the descending colon just above the rectum before grabbing on the pubis again. Its main job is to make a kink in the colon to help keep shit in. It’s also a muscle that can be conditioned to relax when you wanna hand “right now.” It’s a key to getting depth and working past the sigmoid! (See Goin' Deep.)

The Grand Staircase: Descending Colon
	First off, physicians got it backward; they thought about food passage and named it the “descending colon” while we more en- lightened beings would have called it the “ascending colon.” The layers that make up the wall of the colon are similar in some respects to those of the small bowel, but the outside of the large colon has little "bulges". .....The bulges are formed by a combination of three long, narrow bands of longitudinal muscles equally spaced around the
circumference of the colon (these cause the triangular shape you see in the photograph). All along these lengthwise bands are longitudinal muscle fibers between the bulges (you can see them in the pic too). (See movie, click here.) .....Anyway, it’s a longish tube with muscular walls that’s attached to the back of the body—not free-floating. That’s important ‘cause you need to know that it can be ripped away if you’re not experienced and careful. That would classify as a nasty. .....When I’m training a new top, I tell them to think about working up the sleeve of a coat from the cuff; you have to wriggle & cajole so it doesn't get hung up as you work north.

The King's Balcony: Transverse Colon

.....If someone can get their hand turned into your transverse colon, you just might be able to take a whole forearm—or more! The transverse colon "floats", depending largely on how full your tummy is, but it's roughly a shallow curve and at the level of the 10th rib. The transverse colon is bound to the diaphragm opposite the 11th rib by a fold of filmy tissue called peritoneum. This picture shows the union of the descending and transverse colons. To learn more, click here.