A review of rectal anatomy and why it matters
Hi all! Let’s chat about the importance of your poo and what it can be telling you. To start, it’s important to state that I am not a dietitian and cannot provide specific dietary advice. That being said, there have been more and more people coming into office with questions about constipation and poo. So, let’s start with some anatomy! I am a physical therapist after all….
Important anatomy:
The colon: it is comprised of the ascending colon (from the top of your right hip bone to your lowest right rib.); the transverse colon (from just below your right ribs to just below your left bottom ribs); the descending colon (bottom of your left ribs to the top of your left hip), the sigmoid colon (an s-shaped portion that travels from behind the left hip towards the anal canal) the rectum (a short tube from the bottom of the sigmoid colon to the anal canal).
Important Muscles: Internal anal sphincter, external anal sphincter, levator ani group (pubococcygeus, iliococcygeus, ischiococcygeus, puborectalis). Pelvic wall/border: piriformis, obturator internus
Puborectalis: creates a sling where the rectum turns into the anal canal. The ability of this muscle to relax and its strength can contribuite to the anorectal angle.
Anterior Rectal pouch: makes it so that the intestines don’t drop behind the vaginal canal.
Rectal Blood Supply: the key players within the rectum are the inferior and superior rectal veins; there are 5 rectal arteries, however. 1 superior, 2 inferior, and 2 middle.
The Anal Canal: has both sympathetic (think: fight or flight response!) and parasympathetic (think: rest & digest) nerves. The internal anal sphincter (involuntary contractions), the external anal sphincter (voluntary contractions).
Having an understanding of the anatomy can help understand some common issues. Now, in general, if the poo is going to get stuck anywhere, it is often where there is a curve in the colon, rectum, and/or anal canal. Further, the consistency and frequency of the poo can indicate what is going on. For example, if the poo is firm, hard to pass, or even comes out in tiny pellets, there could be some elements of constipation, a lack of soluble fiber (the stuff that helps keep you moving), or even too much insoluble fiber (the stuff that makes your poo bulkier). More on that in a later post. Conversely, if the poo is too runny, it can sometimes be due to inadequate amounts of insoluble fiber and even too much soluble fiber. (Again: major reminder that it’s not in my scope to tell you specifically what is needed for you. That’s to discuss with a dietitian or GI specialist). The consistency of the stool can also indicate where in the colon the poo either spends too much time, or not enough time. Cool, right??
How can the pelvic floor contribute to colorectal health? If there is any degree of vaginal tearing that occurs during birth, this can play a role in the pelvic floor anatomy, and contribute to issues passing fecal matter. Further, it is also possible for the muscles around the rectum to be too tight, which can make it increasingly difficult to pass stool. These muscles can also be less coordinated or not be able to sense the volume of stool properly. This can all contribute to issues passing stool.
Did you know?? In general, you should only need to wipe 2-3x after defecating? There is a term called fecal smearing, which can contribute to the need to keep wiping, and wiping, and wiping, and wiping…
