How the Digestive System Works

Digestive Disorders at the Bottom

People who have celiac disease can't digest wheat products.
Smari/Stone/Getty Images

Let's explore the problems that you might encounter after your food passes through your stomach and enters the intestines. These winding organs can be home to many an ailment, but again, we'll stick to the most common disorders.

  • Inflammatory Bowel Disease (IBD): There are two major types of IBD, a chronic inflammation of the intestines: ulcerative colitis and Crohn's disease. These sometimes debilitating conditions affect more than 600,000 Americans every year [sources: Family Doctor, National Digestive Disease Information Clearinghouse]. Both diseases create ulcers in the intestines, which results in abdominal cramps, diarrhea, intestinal bleeding and weight loss. Crohn's disease generally affects the entire small and large intestines, and ulcerative colitis usually occurs only in the large intestine, beginning at the rectum.
  • Irritable Bowel Syndrome (IBS): Unlike IBD, which is a structural problem in the intestines, IBS is a functional problem. There's no visible damage, like ulcers or tumors, but the intestines are causing trouble. People with IBS can have recurring, unexpected bouts of abdominal pain, bloating, constipation and diarrhea. Many times these symptoms are triggered by ordinary things like stress, hormonal changes and even antibiotics. The exact cause isn't known, but a leading theory is a problem with the signals between the brain and the intestines.
  • Celiac Disease: Here, your immune system is to blame -- it damages the digestive system when you eat gluten, a protein found in wheat, rye, barley and the many foods made with these products. People with celiac disease can't easily digest nutrients from gluten-filled foods and experience diarrhea, abdominal bloating and exhaustion. But they can avoid problems if they keep their diets gluten-free.
  • Tapeworms: Tapeworms aren't as common as other digestive ailments, but they're worth mentioning for the gross-out factor. Tapeworm eggs or larvae enter your digestive tract via contaminated food. Once they've settled into your intestines, they begin stealing nutrients, like vitamin B12. Strangely, most people won't experience any symptoms. But if the freeloading goes on long enough, you can suffer from malnutrition, weakness, nausea, abdominal pain, diarrhea and weight loss. The ultimate danger comes when the worms decide to move into other parts of your body, like your lungs or liver. There, they form cysts that can cause much more serious problems.
  • Flatulence: We all know that everybody farts, but do you know why we do it and how much? Gasses like hydrogen, carbon dioxide and methane are produced during food breakdown in the large intestine. When excess gas is sensed in the rectum, a signal is sent to the brain, which ascertains if it's a good time to release the gas. If it's a go, the sphincters relax, the rectum contracts and a fart is born. An average person produces up to 3 pints of gas per day and will pass it 10 to 25 times a day. If it's happening more often, you might have a digestive issue, like lactose intolerance [source: WebMD: Flatulence].
  • Constipation: An introduction might not be necessary, but constipation is defined as difficult, infrequent or incomplete bowel movements. The meaning of "infrequent" can vary -- anything between three times a day to three times a week is considered normal [source: WebMD]. The bottom line is: If your stools pass without discomfort and are a normal consistency, you're not constipated. This uncomfortable condition is caused a slow-moving large intestine. When stool stays there for too long, too much water is removed, making it hard. While occasional constipation isn't a problem, chronic constipation can lead to painful hemorrhoids or fissures.
  • Diarrhea: Diarrhea happens when muscle contractions cause a person's intestines to move too fast, and the intestines don't have time to absorb water from the waste matter before it's sent out of the body. Intestinal inflammation can also create diarrhea by leaking fluid into the stool. There are numerous causes of diarrhea, from bacteria to stress, so it's no wonder that most Americans suffer around four bouts of it every year [source: WebMD].

To learn more about digestion, take a gander at the links below.


Related HowStuffWorks Articles

More Great Links


  • Auerbach: Wilderness Medicine, 4th ed. Mosby, Inc. 2001. 1483/489.html#4-u1.0-B978-0-323-03228-5..50058-6--cesec104_2969
  • American Society for Bariatric Surgery.
  • Centers for Disease Control: Taeniasis.
  • Cleveland­ Clinic: Gastrointestinal Disorders. health/health-info/docs/1700/1700.asp?index=7040
  • Cohen & Powderly: Infectious Diseases, 2nd ed., Mosby, An Imprint of Elsevier. 2004. 3/683509740/1209/487.html#4-u1.0-B0-323-02407-6..50170-7-- cesec14_4848
  • Discovery Health Gross&Cool Body: Poo.
  • Emedicine: Tapeworm Infestation.
  • Fact or Fiction? Chewing Gum Takes Seven Years to Digest. 3ED24E7&page=1
  • Family Doctor. digestive/disorders/252.html
  • General Anatomy of the Ruminant Digestive System.
  • Heritage, Ford; Composition and Facts About Foods. Soc. of Metaphysicians (1987)
  • Kids Health: Digestive System.
  • Digesting a Hot Dog.
  • Mayo Clinic: Tapeworm Infection.
  • Medtronic: GERD. .do?itemId=1101835641931&itemType=fact_sheet