Understanding Your Gastrointestinal (GI) Tract
Think of your GI tract as a hollow tube within a hollow tube. It starts at your mouth and ends at the anus (special group of muscles that stay tight to keep BM in and relax to let it out). The GI tract consists of an outside layer of longitudinal muscle and an inside layer of circular muscle. Food and liquids taken in by mouth are moved through the GI tract by alternating contractions of one layer of muscle and relaxation (called peristalsis) of the other all the way to the anus.
Initially, your health care provider focuses on understanding your problem by doing a detailed history and physical. From that information different diagnostic tests will be ordered to provide information as to what is wrong and help identify the best treatment approach. Your health care provider will probably begin with the simplest treatment and progress to others if needed. It is important that you be open and honest about your problems. Being a more informed patient about normal functions and why certain things are suggested will make you a good partner with your health care provider in your health care.
Normal Bowel Function
Let’s look at normal bowel function first. After food and liquid have been mixed with digestive juices, the contents are emptied slowly into the small intestine. As the stomach contents are dissolved further by other digestive juices, the contents move further through the small intestines to all the nutrients to be absorbed. They move through to allow for more digestion. The waste products, include undigested food, move into the large colon. This material is called feces. It moves through to the rectum. When the signal is sent to the brain that it is time to have a BM, the muscles around the anus must relax to allow the feces to exit.
Two sets of muscle surround the anus. One is involuntary (Internal Anal Sphincter) and automatically relaxes in order to allow a sampling of contents. This is why a person can tell if the contents are solid, liquid or gas. The other is voluntary (External Anal Sphincter) and surrounds the Internal Anal Sphincter. This is a muscle that we can control. A portion of the pelvic muscles move down to become part of the External Anal Sphincter. This is the muscle that you tighten when you don’t want to pass gas, for example when you’re out in public with other people. If it is not a good time to have a BM, tightening this group of muscles will cause a reaction of deferring the act. The signal to have a BM will not happen again until more feces moves down. This can lead to constipation if you continually defer.
Pelvic Muscles
The pelvic floor muscles are also known as the Levator Ani muscle. The Levator Ani is composed of three muscles that are intertwined. These are the deepest muscles and are also referred to as the pelvic diaphragm. These muscles and other tissues provide support for our pelvic organs (bladder, uterus/vagina, and bowel). One of the muscles of the Levator Ani is the Puborectalis. This muscle is important in bowel continence and in bowel emptying. It begins at the pubic bone (front of the pelvis), goes around the anus and rectum, and returns to the pubic bone. This muscle forms what is called the Anorectal angle. This angle is about 90 degrees and helps to keep fecal material in until a decision is made to go to the bathroom. When sitting to empty the bowel, this angle relaxes to about 110 degrees and allows the contents to be emptied.
The pelvic muscles are like a hammock. They keep our organs from falling out! They start at the pubic bone (in the front of the pelvis) and go to the tailbone (in the back of the pelvis). If you were to look down at the pelvis, it would be like a bowl. The group of muscles that attach the pelvic muscles to the side of the pelvis is another muscle, called the Obturator Internus. The pelvic muscles that aid in bladder and bowel control are like the rotator cuff in the shoulder and are sometimes referred to as the pelvic rotator cuff.
The large leg muscles of the thigh (adductors) and the sphincter muscles (bladder and bowel) are also an important part of the pelvic rotator cuff. There is another layer of muscles below the pelvic diaphragm called the urogenital diaphragm. This muscle group assists with quick tightening actions, like when you sneeze, laugh or cough. All these muscles are voluntary muscles, like in your arms or legs. This means that you can control them. Special pelvic muscle exercises are used to improve their function.
Next: Causes of Constipation