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The Digestive System: An Overview Life is all about using energy. The energy that your body uses comes from the food you eat. This food or fuel is broken down to release its energy and to create building blocks for cell growth and repair in the digestive system. The digestive system makes your body somewhat like a donut with a hole running all through you body. This hole is called the digestive tract and is composed of numerous parts. Look at the diagram on page 847 and list what each of the following parts do. Oral Cavity Pharynx Esophagus Stomach Small intestine Large intestine In addition to this hole you have accessory organs that help the digestive tract do its job. List the accessory organs and say what they do. Read about the functions of the digestive system on page 846 and summarize each in the space below. 1. Ingestion 2. Mechanical Processing 3. Digestion 4. Secretion 5. Absorption 6. Excretion If you cut the digestive tract crosswise, you will discover that it has four layers including (1) the mucosa, (2) the submucosa, (3) the muscularis externa, and (4) the serosa. Read about each of these layers and complete the table below: Wall Layer Subdivisions of the layer Major Functions Mucosa Submucosa Muscularis externa Serosa The two layers of smooth muscle in the muscularis externa play an important role in moving material along the digestive tract. The two layers are arranged in different directions. The Inner layer is arranged so that the muscle fibers run in a ____________ while the outer layer has muscle fibers that run ________________________. The contractions of these two layers create two different kinds of movement. Movement through _______________ helps move material along the tract and _________________ helps in the mechanical processing of material. Describe these two kinds of movement below: 1. 2.
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