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The Digestive System
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The Digestive System
ben999_@excite.com The digestive system is a group of organs that perform the process by which food, containing nutrients, is eaten and broken down into different components. This breakdown makes it possible for the digested material to pass through the intestinal wall into the blood stream. The digestive process contains many different steps that take place in many different organs. The first step of digestion begins at the mouth, where the food enters the mouth. Saliva is secreted from the salivary glands. The saliva contains enzymes such as Ptyalin, which starts sugar digestion. The enzymes also provide lubrication to help in the chewing and swallowing of the food. The food then goes down the esophagus and into the stomach, where the next step of digestion takes place. In the stomach, a mixture of hydrochloric acid and Pepsin, which is secreted by the stomach wall, liquefies the food. At the same time, a substance called intrinsic factor binds Vitamin B in food and various gastric enzymes, such as Pepsin (which begins protein digestion), which are secreted by the stomach wall. Secretions of mucus protect the stomach from its digestive enzymes. The food is then mixed in the stomach, turning it into chyme(digested food). The muscular pumping motion called peristalsis churns the chyme around. The chyme then passes through the pyloric valve by peristalsis to the first portion of the small intestine, the duodenum. The duodenum is where most of the che...
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