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Anatomy of the Digestive System
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The long path of food:

Esophagus: During swallowing, a flexible flap of tissue called the epiglottis reflexively closes over the windpipe to prevent choking. Once swallowed, the food is pushed by wavelike muscle contractions (peristalsis) through a collapsible tube (esophagus) to the stomach.

LES: At the bottom end of the esophagus, where it joins the stomach, food passes through a one-way valve called the lower esophageal sphincter (LES). This valve normally opens when you swallow, which allows food to enter the stomach, then closes quickly which prevents the relux of stomach acid back into the esophagus.

In the stomach, peristaltic waves of muscle contractions, mix up the food with stomach acids and enzymes. This mixing and mashing process breaks down the food so that it can be digested.

The amount of time that food stays in the stomach varies from person to person and also depends on a number of factors:

  • Type & consistency of food: Liquids and starches empty most rapidly. Protein and semisolds move through the stomach at an intermediate rate. Fats and solids empty slowly. Thus, a person will usually be hungry sooner after a breakfast of orange juice, cereal and toast versus a breakfast of bacon, eggs, and milk.
  • Hunger: A meal eaten at a time of intense hunger will tend to leave the stomach more rapidly than normal.
  • Exercise: Mild exercise, especially just after eating, tends to shorten the emptying time of a meal. Strenuous exercise, however, can temporarily inhibit gastric muscle contractions and delay emptying.
  • Position: In most people, lying on the right side can facilitate gastric emptying. This position puts the intestine below the level of the stomach. Lying flat on the back can cause the contents of the stomach to pool in the upper part of the stomach and cause a delay in emptying.
  • Emotions: Strong emotional states are well known to exert significant reactions in gastric activity.
  • Pain: Severe or prolonged pain can inhibit gastric motility and emptying.
  • Pylorus: A ring of muscles which serves as a gate between the stomach and the small intestine. The pylorus opens periodically allowing the contents of the stomach to empty into the duodenum, the first segment of the small intestine.

    The small intestine, also known as the small bowel: The small intestine continues breaking down the food and absorbs most of the nutrients. (The word "small" refers to the diameter of the small intestine, which is narrower than that of the large bowel. Actually the small intestine is the longest segment of the digestive system -- about 20 feet. The coiled loops of the small intestine fill most of the abdominal cavity.)

    The small intestine consists of 3 divisions: the duodenum, the jejunum, and the ileum.

    The ileum of the small bowel joins the colon in the right lower abdomen. This is where the appendix is attached to the colon, or large intestine.

    The colon: (also called the large bowel or large intestine) is a muscular tube about 5 feet long. The large intestine consists of the colon and the rectum. The colon is the first 4 to 5 feet of the large intestine, and the rectum is the last 4 to 5 inches of the large intestine. The part of the colon that joins to the rectum is the sigmoid colon. The colon continues to absorb water and mineral nutrients from the food and is a storage place for waste matter. The waste matter left after this process is feces and goes into the rectum, and from there it passes out of the body through the anus.

    Internet References

    (1) National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Health
    (2) National Cancer Institute
    (3) Physician locator from the American College of Gastroenterology

    --Written by N Thompson, ARNP and M Thompson MD, Internal Medicine, Last updated May 2010

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