The digestive system takes in food, breaks it down (digests), sends the usable parts off into the blood and gets rid of the waste. There are many organs involved in the digestive system. They are broken down into two groups: The gastrointestinal tract (GI tract), which includes all the organs that food passes through in the body, and the accessory digestive organs, that break down food through action (like chewing) or chemicals (like saliva). The GI tract includes: the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The accessory digestive organs include: the teeth, tongue, salivary glands, liver, pancreas and gall bladder.
The mouth (oral cavity) is where digestion begins. In the mouth are the teeth, tongue and the salivary glands. The teeth chew the food and begin mechanical digestion. The tongue moves the food around to help break it down and mix it with saliva. Saliva is secreted by the salivary glands to begin the chemical breakdown of starchy foods (like bread). Food is chewed and rolled into a bolus (lump) to be swallowed. When you swallow food, it passes through the pharynx (back of the throat) down into the esophagus. The esophagus is a long, muscular tube about 10 inches long (25 cm). Food passes down it to reach the stomach. The muscles of the esophagus contract to squeeze the food downward. This is called peristalsis. Food must pass through the cardiac sphincter at the bottom end of the esophagus to enter the stomach. This muscular valve keeps the stomach contents, once mixed with stomach acids, from re-entering the esophagus and burning its unprotected lining.
Assess Digestive System comprehension with the Mutiple Choice Test.
Visual Aids and Assessment:
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Amsel, Sheri. "Digestive System Overview" Exploring Nature Educational Resource ©2005-2019. November 19, 2019
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