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.
Causes of Constipation
There can be many causes of constipation.
- not enough fiber in the diet
- not enough physical activity
- not enough liquid leading to dehydration
- ignoring the urge to have a BM
- excessive use of laxatives
- changes in your life or routine such as pregnancy and travel
- milk thought to be caused by protein in cow’s milk
- Irritable Bowel Syndrome (IBS)
- medications
- problems with the colon and rectum or pelvic muscles
- specific diseases or conditions, such as stroke, Parkinson’s
- problems with intestinal function (motility dysfunction)
Dietary Fiber
Most people eat only about 5 to 14 grams of fiber daily. The American Dietetic Association recommends 20 to 35 grams daily. Fiber sources from fresh fruits, vegetables and grains provide both soluble and insoluble forms of fiber that are essential for formed stool. A diet of mostly refined and processed foods will provide a diet that has had the natural fiber removed. Read the labels of cereal, beans and other canned foods or frozen foods for fiber content. For example the cereal, Fiber One has 14 grams of fiber per serving.
While receiving the appropriate amount of fiber from the diet is preferable, there are fiber supplements available over the counter. Remember to read the label and follow the directions, especially the needed water.
Physical Activity
The simplest way to increase physical activity is to walk. Walking 20-30 minutes a day helps not only your bowel function but also your pelvic muscles. Be sure to check with your health care provider before beginning any exercise program.
Fluid Intake
It is generally accepted that 6-8 glasses of fluid be taken in daily. Be careful with caffeinated and alcoholic drinks as they are dehydrating.
Ignoring the Urge
When you ignore the urge, it will not occur again until more feces returns to the rectum. By continuing to ignore the urge the fecal material will become hard and be difficult to evacuate. A person might also experience more liquid fecal matter seeping around the hard feces leading to bowel leaking.
Laxatives
While fiber helps regulate the bowel it is not considered a laxative. The notion of needing to have a BM daily has played a part in our spending $725 million a year in 1995. Using a laxative continually can lead to becoming dependent on the laxative.
Changes in Life or Routine
Pregnant women may experience constipation due to hormonal changes or because the growing uterus is pushing down on the intestine. As we age, we may experience constipation due to slower metabolism and slower motility in the colon. Traveling may cause changes in routines in both in activity and diet.
Milk
The protein in cow’s milk is thought to contribute to constipation. A change to soymilk may be helpful.
Irritable Bowel Syndrome (IBS)
IBS affects about 10-20% of the general population. It is the most common functional disorder diagnosed by Gastroenterologists. Persons with IBS will generally experience abdominal discomfort and altered bowel habits with either chronic or recurrent constipation or diarrhea or both.
Medications
Many medications can cause constipation. The following is a list of categories that may affect bowel function:
- pain medications (especially narcotics)
- antacids that contain aluminum and calcium
- blood pressure medications (calcium channel blockers)
- drugs for Parkinson’s
- antispasmodics
- antidepressants
- iron supplements
- diuretics
- anticonvulsants
If you are experiencing constipation and are taking any of these types of medications, discuss the problem with your health care provider – don’t stop taking them unless advised to do so by your health care provider.
Problems with Colon, Rectum or Pelvic Muscles
Constipation may be caused by an obstruction in the intestines, by adhesions or a tumor (benign or cancerous), a narrowing of the colon or rectum (stricture), diverticulosis or Hirschprung’s disease. Pelvic muscle dysfunction may be caused by a weakness or excessive activity of the pelvic muscles. It may affect bladder and/or bowel function or pelvic/rectal pain. The pelvic muscles may have learned to contract instead or relax to empty the bowel. Biofeedback can be an effective tool to rehabilitate these muscles and for the person to learn to control.
Specific Diseases or Conditions
Constipation may be caused by neurological, metabolic and endocrine disorders or systemic disorders the affect organ systems. These disorders can slow the movement of stool through the colon, rectum, or anus. The following is a list of these disorders:
- Neurological disorders
- stroke
- multiple sclerosis (MS)
- Parkinson's disease
- spinal cord injuries
- chronic idiopathic intestinal pseudo-obstruction
- Metabolic and endocrine conditions
- diabetes
- uremia
- hypercalcemia (too much calcium)
- poor glycemic control (sugar)
- hypothyroidism (low thyroid)
- Systemic disorders
- amyloidosis
- lupus
- scleroderma
Intestinal Function (GI motor disorders)
GI motor disorders are caused by a dysfunction in the Enteric Nerve System which is between the longitudinal and circular muscles of the GI tract. Colonic inertia and delayed transit are caused by a decrease in muscle activity in the colon. These syndromes may affect the entire colon or may be confined to the lower, or sigmoid, colon. Some people, who have GI motor disorders, may also have problems in the small intestines, stomach and esophagus.
Next: Diagnoisis and Treatment Options