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Digestive_System

2013-11-13 来源: 类别: 更多范文

Digestive System The digestive process is important in maintaining the lives of living organisms and in providing them with needed energy. Groups of organs, such as the mouth, esophagus, stomach, and intestines, work together to perform this complex task. Digestion is the process of breaking down food from large molecules into small ones to make it easier for absorption. The three major steps involved in the digestive process are ingestion, digestion, and absorption. Ingestion, which occurs in the mouth, is the first step of the digestive process. After food enters the mouth, the teeth chew it. Saliva, which is produced by the salivary glands, plays a major role in breaking down the food into smaller pieces. These small pieces travel to the stomach through the esophagus. In the stomach, the second step of the digestive process begins. When the chewed food reaches the bottom of the esophagus, a valve lets the food enter the stomach. Contraction of the stomach wall mixes the food. Acidic gastric juices, which are small, food, process, stomach, digestive, digestion, absorption, mouth, intestine, ingestion, step, molecules, major, esophagus, wall, villi, three, takes, steps, secreted, reaches, providing, place, pieces, occurs, needed, lives, glands, gastric, enter, energy, breaking, begins, absorbed, work
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