3. Investigate how foods move through the digestive tract. 4. Explore the function of mucus in the digestive tract.

Transcription

1 Lesson Objectives: 1. Discuss the purpose of the digestive processes. 2. Build a model of the digestive tract. 3. Investigate how foods move through the digestive tract. 4. Explore the function of mucus in the digestive tract. 1

2 1. How do you think food moves through the digestive tract? Food is taken into the mouth. Peristalsis, the wavelike motion of the circular and longitudinal muscles lining the digestive tract, moves the food through the tract. Mucus, the slippery substance lining the walls of the digestive tract, helps food move through more easily. Sphincters (narrow areas of thickened muscles) control food moving from one part of the digestive system to another. The food goes from mouth to esophagus into stomach. From the stomach it travels through the pyloric sphincter into the small intestine, then the large intestine, to be stored as waste in the rectum. Undigested food is eliminated from the body through the anus. 2

3 2. What do you think happens to food as it moves through the digestive tract? Food is broken down into smaller and smaller pieces through mechanical and chemical digestion. It must be broken down into molecules that are small enough to enter cells. (Mechanical digestion includes the tearing and grinding of food by your teeth, the mashing action of the tongue and the churning of the muscles lining the digestive tract. Chemical digestion relies on the digestive enzymes and acids in your system.) 3

4 3. Why do you think the digestive tract gets narrower at some places? These narrow places are called sphincters. Sphincters are muscles that control the speed of the passage of food through the digestive system. They also help make sure that food moves through the digestive system in only one direction. Sphincters are found between organs of the digestive(top and bottom of the stomach) system and at the opening and end of the digestive tract (lips and anus). What did the tennis ball, oil, and tube represent? The tennis ball represents swallowed food; the oil represents mucus; the tube represents the digestive tract. 4

5 2. What does the tennis ball represent? Swallowed food 3. Why do you think the tennis ball was soaked in oil? The oil simulated mucus, a slippery substance that coats the lining of the digestive tract. 4. What is the function of mucus? Mucus permits food to move more easily and protects the lining of the digestiv tract from the digestive enzymes. 5. Compare and contrast the movement of food as it passes through the digestive tract with the movem of the tennis ball. Compare: They both moved a substance along a tube using a squeezing action The tube and tract are the same length. Contrast: The ball stays the same size. In the digestive tract, food particles would get smaller, and their chemical composition would change. The tube do not vary in width no sphincters. Food moves too quickly. 5

6 Compare and contrast the movement of food as it passes through the digestive tract with the movement of the tennis ball. Alike: o The tennis ball moved from the beginning of the tube and came out the other end, just as food passes through our digestive tract (mouth to anus one direction). o The oil helped the ball move through the tube just like mucus helps food pass through the digestive tract. o The tube was the approximate length of the human digestive tract. o The parts were labeled in the correct order. o Wavelike movement of the hands moving the ball through the tube simulated peristalsis. Different: o The tube was the same size from beginning to end and stretched the length of the room. The different organs have different diameters and are coiled and compact in our bodies. o The tube was plastic and our DT is made of living tissue, mostly muscle cells. o The tube did not have anything separating the organs. The DT has sphincters separating the organs from mouth to rectum. o Even thought the ball moved through the tube, the ball stayed the same size. Food in the digestive tract would undergo mechanical and chemical digestion. 6