How the Digestive System Works

Digestive Problems at the Top

If you swallow air while you're eating, you might burp.
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With all the steps involved, there are bound to be some bumps in the digestive road. Many of the following digestive problems may seem relatively harmless, but approximately 14 million people end up hospitalized each year because of them [source: National Digestive Diseases Information Clearinghouse]. The full list is probably too long to keep most people's attention, so we'll discuss a few of the most common -- starting from the top.

  • Belching: Some people are better at it than others, but all burping is the result of the same factor: air. If you drink bubbly beverages or swallow air when eating, air collects in the stomach and then gets pushed back out your esophagus and quickly out the mouth. Three to four burps after a meal is considered normal -- more than that and you might have a medical condition, like an ulcer.
  • Vomiting: Vomiting is the forceful expulsion of stomach contents up through the esophagus, usually propelled by the abdominal muscles. One of the most common reasons for vomiting is foreign bacteria that have hitched a ride on your food. Once those bacteria irritate the gastrointestinal system, a signal is sent to the brain and vomiting soon commences. Viral stomach infections are no better -- they can cause vomiting for days until the virus is out of the body. Another digestive reason for vomiting is a food allergy, like lactose intolerance. If the food itself isn't the problem, you might want to watch the overeating, another common cause of vomiting.
  • Gastroesophageal Reflux Disorder (GERD): Symptoms of this chronic digestive disorder are seen in nearly 22 million Americans and cause more than 700,000 hospitalizations each year. People who suffer from GERD essentially have a lazy esophageal sphincter, that valve connecting the stomach and the esophagus. The lazy sphincter allows acidic stomach contents to come back up into the esophagus. The presence of all this acid in the esophagus results in a burning sensation in the middle of the chest, better known as heartburn [source: National Digestive Diseases Information Clearinghouse].
  • Peptic Ulcers: A peptic ulcer is essentially a hole in the lining of the stomach or the first part of the small intestine. Once thought to be a reaction to stress, it is now known to be caused by an invasion of the Helicobacter pylori bacterium or of certain medications, like anti-inflammatory drugs. These culprits manage to weaken the protective mucous in the stomach and allow acid to eat through.
  • Stomach Bug: It's no accident that an illness that involves cramps, abdominal pain, diarrhea and vomiting is referred to as a "bug." That's because most gastrointestinal infections are caused by unwanted bacteria, viruses and parasites. The names of these little germs depend on where you live, but the most common offenders in the United States include salmonella, shigella, E. coli bacteria and the parasite giardia.
  • Lactose Intolerance: Lactose intolerance, which affects up to 50 million Americans, is the inability to digest the major sugar in milk [source: National Digestive Disease Information Clearinghouse]. If you're lactose intolerant, your digestive system doesn't produce enough of the enzyme lactase, which is found in the small intestine. So, it doesn't break down milk into simpler sugars that the body can digest. Those with lactose intolerance experience mild to severe nausea, cramps, bloating, gas or diarrhea, usually 30 minutes to two hours after ingesting a dairy product.

We've covered the throat, the stomach, and even a tiny bit of the small intestines. But plenty of problems occur below the stomach, too. We'll discuss the most common digestive problems below the belt in the next section.