POGIL Activity on The Digestive System (Let s go Down the Hatch! ) Life is organized in the following levels: Chemical Level, Cellular Level, Tissue Level, Organ Level, Organ System Level, and finally, Organism. In this POGIL, we will explore the Digestive system. Recall that there are four types of macromolecules: Carbohydrates, Lipids, Proteins, and Nucleic Acids. We will be exploring how the digestive system works to break down and absorb these organic compounds for optimal use and remove the waste products that are indigestible. Objectives: 1. Students will be able to describe the overall function of the digestive system. 2. Students will be able to outline the steps of the digestive process and identify major organs associated. MODEL 1: Our food provides the building blocks that our cells need to perform all the chemical reactions needed to sustain life. Humans have a digestive tract (gut) that runs from the mouth, through the body, and ends at the anus. There are accessory organs that assist in digestion such as the liver, gall bladder, and pancreas. The digestive process involves five activities known as: ingestion (eating), movement of food, digestion (breakdown of food), absorption (taking in nutrients from food), and elimination (removal of waste.) 10 minutes 1. Record the 5 activities of the digestive system and use each term in its own complete sentence. The first one is done for you. a) Ingestion: The girl smiled as she ingested her ice cream. b) c) d) e) Word Bank: Liver, tongue/teeth, anus, rectum, colon (large intestine), pancreas, esophagus, stomach, small intestine, appendix, gall bladder Identify the numbered structures in the model above. Some words may be used more than once! 1. 5. 9. 2. 6. 10. 3. 7. 11. 4. 8. 12.
MODEL 2: 6 minutes The oral cavity is composed of the cheeks, hard and soft palate, and tongue. This cavity contains specialized structures known as teeth which aid in a process called mastication or chewing (mechanical digestion). The tongue helps to move food around and the salivary glands secrete saliva that begins the process of chemical digestion. 1. List two major roles of the Oral Cavity. 2. List 2 structures within the oral cavity and explain the function of each. 3. As food is moved back into the pharynx, there appears to be two tubes or passageways that the food could go down. Which tube will lead to the stomach? 4. What structure (labeled in the diagram) will prevent food from going down the wrong pipe? 5. Record the 3 types of salivary glands as shown in the model to the right. Note the location of each. 6. What are these glands secreting? What type of digestion does this substance assist with?
MODEL 3: 10 minutes After the food (now called a bolus) moves down the esophagus, it will pass into the stomach. The stomach continues the process of both mechanical and chemical digestion. There are two circular muscles at each end of the stomach that tighten when it is time for the muscles of the stomach to contract, physically churning and mixing the food. This prevents stomach contents from coming back up into the esophagus. After 2-3 hours, the liquefied remains (chyme) move out of the stomach slowly through another circular muscle (pyloric sphincter) and into the small intestines. The first part of the small intestine called the Duodenum allows for the last of the chemical digestion to take place with more enzymes secreted from the pancreas and bile from the gall bladder. Total time of digestion is between 6-8 hours. 7. Use the information above to label the Esophagus, Esophageal sphincter, Stomach, Muscular Walls, Pyloric Sphincter, and Duodenum. RUGAE: The stomach folds that allow for expansion of the stomach. 8. What is a Sphincter? Name 2 of sphincters found in the stomach. Put a star above the one that empties chyme into the small intestine. 9. Trace the flow of food from the oral cavity into the Duodenum.
MODEL 4: Chemical digestion is necessary to hydrolyze the macromolecules in our food into its monomer parts that are easy to get into our cells. Enzymes along the digestive tract and from accessory organs play a key role in breaking down these large compounds. 5 minutes 10. Using the information above label the diagram below with where EACH enzyme is located, what macromolecule is being digested, and indicate its ph level. (Use a ruler for label lines)!
MODEL 5: 15 minutes After the Duodenum, digestion ceases and the majority of absorption begins (glucose, aspirin, and alcohol will be absorbed directly into the bloodstream from the stomach). Nutrient absorption occurs in the last 2/3 of the small intestine and water absorption occurs in the Colon or Large Intestine. 11. Given the above information, why is it adivsable to eat while consuming alcohol? 12. After digestion, where does a majority of the nutrient absorption take place? 13. Color the Duodenum Red, the Jejunum Orange, the Ileum Yellow, and the Large Intestine Green. Large Intestine Read this! The intestinal tissues are arranged in many folded projections called Villi. Each individual cell is topped with folded projections called microvilli. 14. Why do you think the intestines have all of these folded surfaces? 15. The Colon is responsible for removing water from the now waste material. What condition might result if too much water is removed from waste? What condition may result if too little water is removed? 16. Feces is stored in the rectum until the urge to eliminate takes place. Through what opening is feces eliminated from?
The Liver is a large organ that weighs about 3 pounds. It carries out many functions that help our bodies maintain homeostasis, but for digestion, it produces a soapy substance called Bile. Bile is a greenish basic (ph 7.5-8.5) liquid that helps to break up fats in the small intestine (duodenum). This substance also helps to neutralize the acidic chyme coming from the stomach. The gallbladder is a small organ located underneath the liver. It s function is to store the bile that the liver produces, and then slowly release it into the duodenum via the common bile duct. 17. Identify the source of Bile. 18. What is the function of Bile in digestion? 19. Describe the role of the gallbladder in digestion. 20. You can t live without your liver, but can you live without your gallbladder? How might the digestive process adapt if it is removed? 21. Trace the flow of food through the entire digestive system using arrows to move from structure to structure. Include at least 12 organs/accessory organs in your response.