Grade 8 Unit 14: Digestive System Lesson 2 PDF

Grade 8 Unit 14: Digestive System LESSON 14.2 Processes in the Digestive System Table of Contents Learning Competency...

Grade 8 Unit 14: Digestive System LESSON 14.2 Processes in the Digestive System Table of Contents Learning Competency 1 Learning Objectives 1 Suggested Time Frame 1 Essential Questions 1 Prerequisite Topics 2 Lesson Proper 2 A. Introduction to the Lesson 2 B. Discussion 11 C. Practice and Feedback 21 Performance Assessment 23 Synthesis 25 Bibliography 27  Grade 8 Unit 14: Digestive System Unit 14 | Digestive System Lesson 2: Processes in the Digestive System Learning Competency At the end of this lesson, the given DepEd learning competency should be met by the students. Explain ingestion, absorption, assimilation, and excretion (S8LT-IVa-13). Learning Objectives In this lesson, you should be able to do the following: Explain the processes involved in the digestion of food. Discuss how each organ is involved in these processes in the digestive system. Suggested Time Frame 1 session (or approximately 50 minutes) Essential Questions At the end of this lesson, the student should be able to answer the following questions. What are the functions of the digestive system? What are the components of the digestive system and their functions? How does digestion occur? 1  Grade 8 Unit 14: Digestive System Prerequisite Topics The students should know the following prerequisite topics before proceeding with the lesson. The five senses Stomach and intestines Connections between body organs Levels of biological organization Cell as the basic structural and functional unit of life Lesson Proper A. Introduction to the Lesson Start the lesson by introducing the following concepts and/or asking the following questions to the students. The suggested activities after the questions may also be done in class. You may use any of the suggested activities below. Link to the downloadable presentation slides: 14.2. Processes in the Digestive System 1. Recall the muscular system with an emphasis on its general function and types of muscles. What is the major function of the human muscular system? What are the different types of muscle tissue? a. The muscular system allows the body to move. b. Three kinds of muscles exist based on their tissue type. i. The skeletal muscles, which mainly function for movement, are those that are attached to the bones via the tendon. ii. The cardiac muscles make up the heart, and they are all connected to be able to move altogether. iii. The smooth muscles are found as a layer of tissue in different body 2  Grade 8 Unit 14: Digestive System organs such as the stomach, intestines, and the surroundings of the lungs. c. Muscles may also be grouped according to the control of their movement. i. Voluntary muscles are those that can be moved at will and require conscious effort. These include the skeletal muscles. ii. Involuntary muscles are those that move and function without conscious control. These include the smooth muscles and cardiac muscles. d. You may use Option A as an activity to supplement the recall of the muscular system. Option A: The Muscular Skit This activity will allow the students to recall the activities of the three types of muscle tissues and their types of control. Duration: Approximately 10 minutes Procedure: 1. Divide the class into three groups. 2. Randomly assign to each group the following muscle tissues. a. skeletal muscle b. cardiac muscle c. smooth muscle 3. Each group must prepare a two-minute skit that will highlight the following aspects of the muscle tissue assigned to them. a. their location b. their type of control c. at least three of activities or processes that require their action (except for the cardiac muscle) 4. They will be given five minutes to prepare. 5. Afterward, ask each group to present their skits. 6. Guide them as they present their skits. Provide them points for correction 3  Grade 8 Unit 14: Digestive System when necessary. You may use the sample answers in the table below as a guide in evaluating the content of their skit. Answer Key: Muscle Location Control Activities or Type Processes These muscles are They are Movements of attached to the bones; under the facial examples include the conscious muscles; the biceps and triceps of the control, movement of arms and the hence arms when gastrocnemius of the legs. voluntary. manipulating Skeletal objects; the movement of the legs when running or walking; maintenance of posture. These muscles make up They are The continuous the heart. under pumping action unconsciou of the heart is to Cardiac s control, drive blood flow. hence involuntary. These muscles make up They are The movement the walls of the under of food down gastrointestinal tract and unconsciou the the blood vessels. s control, gastrointestinal Smooth hence tract; the involuntary. maintenance of blood pressure; facilitates secretion of 4  Grade 8 Unit 14: Digestive System substances from glands. Guide Questions: 1. What does it mean when a muscle is voluntary? Answer: This means that the muscle needs conscious input for it to move. 2. What function do cardiac muscles have? Answer: Cardiac muscles are responsible for pumping blood throughout the body. 3. What will happen if smooth muscles of the digestive system fail to function? Answer: Peristalsis will not be possible. Teacher’s Notes This activity serves as a springboard to the discussion of the propulsion of food along the gastrointestinal tract, which is facilitated by the smooth muscles that line in its wall. 2. Recall the circulatory system. What is the major function of the circulatory system? What are the major components of this organ system? a. The circulatory system is responsible for the transport of materials such as nutrients, hormones, and gases throughout the body. b. This organ system is composed of the following structures. i. The blood is a connective tissue that serves as the medium of transport of dissolved nutrients and hormones, as well as oxygen and carbon dioxide. ii. The heart is the muscular pump that provides force for blood flow. iii. The blood vessels are conduits for the flow of blood throughout the body. Arteries carry blood away from the heart, veins carry blood toward the heart, and capillaries are sites for the exchange of materials between the blood and tissues. c. You may use Option B to supplement the recall of the circulatory system. 5  Grade 8 Unit 14: Digestive System Option B: Relate and Circulate This activity will allow the students to play a charades game involving the components of the circulatory system. Duration: Approximately 15 minutes Teacher’s Preparation: 1. printed paper lots that contain the following words: a. heart b. artery c. veins d. capillaries e. red blood cells f. white blood cells g. platelets h. blood i. plasma Procedure: 1. Divide the class into two big groups. 2. If possible, you may ask one of the groups to step outside of the class. 3. Provide the first group with the paper lots, and tell them that they will be given as many turns as they can for three minutes. In each turn, a member of the group will act out the picked word. The rest of the team shall correctly determine the word. 4. If they correctly guessed the word, another member should be tagged in and must act out another word. 5. Note the number of words that they can correctly guess for three minutes. 6. Perform steps 3 to 5 for the other groups. You may provide incentives to the group who have garnered more points. 7. Afterward, call on random students to define or describe the words from 6  Grade 8 Unit 14: Digestive System the list above as they relate to the circulatory system. You may use the following sample answers as your guide. a. heart: Answer: The pumping organ of the circulatory system that provides the forces required for the blood to flow. b. artery: Answer: A blood vessel that carries blood away from the heart. c. vein: Answer: A blood vessel that carries blood towards the heart. d. capillaries: Answer: The blood vessel that is in close association with the tissues to allow the exchange of materials between them (the tissues) and the blood. e. red blood cells: Answer: A type of blood cell with hemoglobin to allow binding of oxygen for transport. f. white blood cells: Answer: A type of blood cells that functions for immunity. g. platelets: Answer: The solid component of the blood that functions for clotting during wound healing. h. blood: Answer: The special connective tissue of the circulatory system that functions for the transport of the materials throughout the body. i. plasma: Answer: The liquid component of the blood wherein some gases, nutrients, and hormones are dissolved to facilitate transport. Guide Questions 1. How does the circulatory system work in coordination with the muscular system? Answer: The heart pumps the blood through the vessels to supply the muscles with nutrients and gases which they highly require during strenuous activities. 2. How does the circulatory system work in coordination with the respiratory system? 3. Answer: The air sacs of the lungs have numerous capillaries that allow the 7  Grade 8 Unit 14: Digestive System diffusion of oxygen and the release of carbon dioxide. The circulatory system then delivers oxygenated blood to the tissues and picks up deoxygenated blood to be delivered to the lungs. 4. How does the circulatory system work in coordination with the digestive system? Answer: The digestive system’s small intestine is also dense with capillaries to allow the transport of the absorbed nutrients to the organs. Teacher’s Notes This activity will serve as a springboard to the discussion of the absorption process that takes place in the walls of the small intestine. This will help the students clearly establish the connection between the functions of the digestive and the circulatory system. 3. Recall the digestive system. What are the general functions of the digestive system? What are the major divisions of this organ system? a. The digestive system functions for the breakdown of food into absorbable units. It has the following major divisions. i. The mouth region consists of the lips, teeth, tongue, and palate, that all cofunction to mechanically digest food. ii. The gastrointestinal tract is a long tube consisting of the esophagus, stomach, small intestine, large intestine, rectum, and anus. iii. The accessory organs are not part of the track, but they produce secretions that facilitate the process of digestion. They include the salivary glands, liver, and pancreas. b. You may use Option C as an activity to supplement the recall of the organs of the digestive system. Option C: Labelling Organs 8  Grade 8 Unit 14: Digestive System This activity will allow the students to recall the components of the digestive system. Duration: Approximately 15 minutes Materials: cardboard coloring and drawing materials glue markers oslo papers scissors Procedure: 1. Step 1. Ask the students to form groups with five members each. 2. Instruct them to draw the organs of the digestive system in an oslo paper. Ask them to cut the organs afterward. 3. Their model must distinctly include the following structures, that should also be labeled. a. lips b. teeth c. tongue d. pharynx e. epiglottis f. esophagus g. stomach (cardia, fundus, and pylorus must be labeled) h. small intestine (duodenum, jejunum, and ileum must be labeled) i. large intestine j. rectum k. anus 4. Let them glue their models on the white portion of the illustration board. 9  Grade 8 Unit 14: Digestive System 5. After they have finalized their models, ask them to draw a pointer from the structure and, at the end of the pointer, ask them to write the corresponding primary function. 6. When done, let them exhibit their work around the classroom. Let the students view the outputs of the other group. 7. Let their outputs be displayed while discussing the next lesson on the processes in the digestive system. 8. Conclude this activity by answering the guide questions. Guide Questions 1. What are the three divisions of the human digestive system? Answer: These three divisions of the human digestive system are (a) the mouth or oral cavity, (b) the gastrointestinal tract, and (c) the accessory organs. 2. What are the important processes that take place in the digestive system as discussed in the previous lesson? Answer: These important processes include the mechanical and chemical digestion, propulsion of food along the tract, absorption, and excretion. 3. What organ system works in tandem with the digestion system to ultimately fulfill its function? Answer: The digestive system coordinates with the circulatory system to facilitate the transport of the absorbed nutrients to the other organs. Teacher’s Notes This activity will serve as a springboard to the discussion of the processes that take place in the digestive system, i.e., mechanical and chemical digestion, propulsion, absorption, and excretion. 10  Grade 8 Unit 14: Digestive System B. Discussion After doing the introduction activity, the teacher can now proceed discussing the actual lesson using the flow below. 1. Discuss ingestion, propulsion, and digestion events that take place in the digestive system. How does the digestive system facilitate ingestion, propulsion, and digestion? a. The journey of food starting from the mouth down to the anus can be summarized by a sequence of events namely, ingestion, propulsion, digestion, absorption, assimilation, and excretion. b. Ingestion is the first event that takes place in the digestive system. i. It is the process of taking in food into the mouth and gastrointestinal tract, that also involves salivary action and physical breakdown of food through mastication. ii. Saliva has the enzyme amylase. This enzyme is responsible for breaking down starch (sugars in plants) and glycogen (sugars in animals). c. Propulsion is the movement of food down that gastrointestinal tract. i. The act of swallowing food, or the act of pushing it backwards by the tongue, is a voluntary type of propulsion. ii. An involuntary type of propulsion known as peristalsis follows. This is when muscles of the gastrointestinal tract involuntarily contract and relax alternately to create rippling movements. d. Digestion is the breakdown of food into smaller molecules for absorption by the body and it involves both mechanical and chemical components. i. Mechanical digestion is the breakdown of food molecules without the use of chemical reactions. It involves mastication, churning, and segmentation. ii. Chemical digestion is the type of digestion that involves chemical reactions. 1. This process of digestion starts in the mouth, but most of the chemical digestion takes place in the stomach and small intestines. 11  Grade 8 Unit 14: Digestive System 2. The presence of food triggers the stomach to release the hormone gastrin. Consequently, gastrin signals the stomach to produce more pepsinogen, mucus, and hydrochloric acid. The high acidity of the stomach brought by hydrochloric acid activates pepsinogen to pepsin which will digest proteins into amino acids. 3. Most of the digestion takes place in the small intestine. a. The bile is released by the gallbladder and liver into the duodenum and it functions for the emulsification of fat. b. The pancreatic juice is also released into the duodenum, and it is a cocktail of different enzymes such as amylases, proteases, and lipases that will serve to break down their respective substrates. 4. The table 14.2.2. summarizes the enzymes/acids that facilitate the chemical digestion of food. Table 14.2.2. Summary of enzymes/acids that facilitate the chemical digestion of food Enzyme/Acid Function Gastrin Signals the stomach to produce pepsinogen, mucus, and hydrochloric acid. Hydrochloric acid Creates an acidic environment for the stomach and helps in the breakdown of fiber. Pepsin Digests proteins into amino acids. Mucus Covers the inner lining of the stomach from acid. Bile Emulsifies fats. Pancreatic juice (amylases, Breaks down macromolecules into corresponding building 12  Grade 8 Unit 14: Digestive System proteases and lipases) blocks. iii. You may use Option A as an activity to supplement the discussion of the digestion process. Option A: Material Digestion This activity will allow the students to simulate the process of mechanical and chemical digestion. Duration: Approximately 20 minutes Materials: candy crackers cups sand sugar water Quipper Reference: Unit 14: Digestive System, Lesson 2: Processes in the Digestive System Procedure: 1. Provide the students with the following procedure. a. Immerse the candy in a cup of water. Stir for one minute and observe. b. Do the same for sand, sugar, and crackers. Observe each. c. Repeat steps 1 and 2, but use soda instead of water. d. Record your observations in the table below. 2. Afterward, answer the guide questions below to conclude this activity. 13  Grade 8 Unit 14: Digestive System Table 14.2.2. Changes in the materials in water and soda after one minute Observations Materials water soda candy sand crackers sugar Answer Key: Observations Materials water soda candy more dissolved less dissolved sand no change no change crackers softening softening sugar more dissolved less dissolved Guide Questions 1. Why do you think some materials shrank while some did not? Answer: Some materials dissolved and some did not because it is in the chemical nature of some to get dissolved in a solvent and for some not to do so. 2. Which made the materials dissolve faster, soda or water? Answer: Between soda and water, the latter allows faster dissolution. 3. How would you relate this activity to the process of digestion? Answer: Sand did not change upon exposure to water and soda. Just like some food materials, exposure to the inappropriate enzyme will not allow digestion. 14  Grade 8 Unit 14: Digestive System Teacher’s Notes This activity will allow the students to look at the specific nature of enzymes and how they facilitate the increased rate of chemical digestion. 2. Discuss absorption, assimilation, and excretion as they relate to the digestive process. How does the digestive system perform absorption, assimilation, and excretion? a. Absorption in the small intestine happens when nutrients from the digested food are absorbed and transported into the bloodstream. i. Capillaries are tiny blood vessels that absorb water-soluble nutrients such as glucose, amino acids, vitamins, and minerals. ii. Lacteals are lymphatic vessels that absorb fatty acids and glycerol. iii. The small intestine also absorbs some of the water, minerals, and alcohol. iv. The large intestine absorbs most of the water and some vitamins. b. Assimilation is the process of building up complex substances after absorption. This process is the opposite of absorption. i. It also involves the movement of nutrients absorbed by the blood. ii. It is an important process for the synthesis of essential compounds, such as hormones and enzymes, for the body to function well. c. Excretion involves the removal of undigested food particles from the body. i. Feces is formed upon the absorption of excess water in the chyme, and it contains indigestible materials like cellulosic fiber from plants, small amounts of water, mucus, and a large number of bacteria. ii. Peristalsis and mass movements in the large intestine move the feces into the rectum. Mass movements are slow and long contractions within the large areas of the large intestine. As feces fills the rectum, a defecation reflex then signals excretion. d. You may use Option B and Option C as activities to supplement the discussion of the overall activity of the digestive system. 15  Grade 8 Unit 14: Digestive System Option B: The Digestion Simulation This activity will allow the students to simulate the process of digestion by using a mashed potato model. Duration: Approximately 20 minutes Materials: boiled and mashed sweet potatoes packaging tape scissors two ziplock bags two ethylene plastic bags (or any thick and transparent plastic bag) filtering cloth three rubber tubes Procedure: 1. Ask the students to cut a hole in a ziplock bag, and connect one end of a rubber tube by using packaging tape. Label this bag the “mouth”. 2. Let them connect the other end of the rubber tube to an ethylene bag and seal the sides of the tube by using tape. Label this ethylene bag the “stomach and small intestine” 3. From the ethylene bag in step 2, ask them to cut a hole and connect it to another tube with a filtering cloth in its mouth. The sides must be sealed by using tape. Ask them to connect the other end of the rubber tube (with filter cloth) to another ethylene bag. This ethylene bag must be labeled as the “tissues”. 4. Instruct them to cut another hole from the ethylene bag in step two, and connect a rubber tube to it. Connect the other end of the tube to another ziplock back. Label this ziplock bag with “colon and rectum”. 5. In the first ziplock back, ask them to combine the sweet potato with water. 16  Grade 8 Unit 14: Digestive System By using their hands, let them mash it. After mashing, ask them to push the food to the tube going through the ethylene bag on the other end. 6. In the ethylene bag, ask them to further mash the potato. Let them have the water pass through the tube with filter cloth. 7. When the potato already ran out of fluid, ask them to push it to the other tube leading to the “colon and rectum”. Let them further push the mashed potato out of the ziplock bag. 8. Conclude this activity by answering the guide questions below. Guide Questions 1. What does the mashing represent? Answer: The mashing of the sweet potato represents the mastication through the teeth and tongue and the contraction of the smooth muscles to allow mechanical digestion. 2. How is absorption represented in the activity? Answer: The water that passes through the tube with filter cloth represents the nutrients being absorbed from the small intestine to the bloodstream. 3. How is excretion represented in the activity? Answer: Excretion is represented when the undigested and unabsorbed food particles are being eliminated via the last ziplock bag. Teacher’s Notes This activity will allow the students to simulate the digestion, propulsion, absorption, and excretion that take place in the gastrointestinal tract. Option C: Digestion in Action This jigsaw activity will allow the students to gain a better understanding of the events in the digestive tract y. Duration: Approximately 20 minutes 17  Grade 8 Unit 14: Digestive System Procedure: Part 1: Expert Group Assignment 1. Divide the class into groups with four members each. Emphasize to them that this will be their base team or jigsaw group. 2. Instruct the base teams to assign to each member one of the following sets of events in the digestive system. They will become an “expert” on that particular event. a. Event 1: Ingestion and Propulsion b. Event 2: Digestion c. Event 3: Absorption and Assimilation d. Event 4: Excretion 3. Ask them to give emphasis on (a) which part (or parts) of the tract the events take place and (b) how the events are accomplished. Part 2: Expert Group Discussion 1. Ask the students to meet with their “temporary” expert groups by having a member from each jigsaw group join students assigned with the same section. 2. Within their expert groups, instruct them to share information among the members by taking turns. Give them 10 minutes to do this. 3. Float among the groups and randomly ask questions to check their understanding. Part 3: Jigsaw Team Discussion 1. Ask the students to return to their base teams. 2. Instruct each member to present their assigned section of the digestive system. 3. Likewise, float from one jigsaw group to another to check students’ presentations. 4. You may use the table below to guide the students as you float from one 18  Grade 8 Unit 14: Digestive System team to another. Student Worksheet Events Structures Processes The food is taken into the mouth, and it is exposed to saliva and physical breakdown. mouth, esophagus, Ingestion and The food is moved through 1 stomach, small Propulsion the peristaltic action of the intestine esophagus. The same muscular contraction moves the food down the stomach and intestines. The mechanical digestion is facilitated by the mastication in the mouth, churning in the stomach, and segmentation in the intestines. During mechanical digestion, more surface of the food is made available for digestion. Chemical digestion is aided by the secretions of the salivary mouth, stomach, 2 Digestion glands, pancreas, liver, and small intestine the cells in the walls of the stomach and small intestine. During chemical digestion, biomolecules are broken down into their subunits. Carbohydrates are broken down into monosaccharides, proteins into amino acids, and lipids into fatty acids and glycerol. Absorption and stomach, small Absorption of water takes 3 Assimilation intestine, place in the stomach and 19  Grade 8 Unit 14: Digestive System capillaries, lacteals, large intestine, with the large intestine former performing it to a lesser extent. Majority of absorption takes place in the small intestines. The capillaries are responsible for the absorption of water-soluble molecules such as monosaccharides and amino acids. Lacteals of the lymphatic system are responsible for the absorption of fats. Assimilation is when the nutrients are being transported by the blood and the molecules are reassembled into complex compounds or used as sources of energy. Excretion is the elimination of undigested food material 4 Excretion rectum and anus consisting of cellulosic fibers and mucus through the anus. Guide Questions 1. What are the events that take place in the oral cavity? Answer: Ingestion and digestion take place in the mouth. 2. What are the events that take place in the stomach? Answer: Propulsion, digestion, and absorption take place in the stomach. 3. What are the events that take place in the small intestine? Answer: Propulsion, digestion, and absorption take place in the stomach. Teacher’s Notes 20  Grade 8 Unit 14: Digestive System This activity will reinforce to the students the discussion on the processes that take place in the digestive system. C. Practice and Feedback Use the following strategies to assess student understanding. Guide the students as they discuss their answers. Immediately provide points for improvement or correction, when necessary. You may use the answers provided below as your guide. 1. Select students from the class to answer each of the following questions. When a student is answering an item, instruct the rest of the class to take notes, especially on concepts they did not clearly understand. a. Enumerate the events that take place in the digestive system to perform its function. Answer: The events that take place in the digestive system for it to properly perform its duty are the following: 1. ingestion 2. propulsion 3. digestion 4. absorption 5. assimilation 6. excretion b. Enumerate the structures involved in ingestion and propulsion and briefly describe the processes involved for them to be accomplished. Answer: Ingestion primarily involves the mouth and the structures in it (i.e., lips, tongue, teeth), while propulsion involves the rest of the gastrointestinal tract and particularly the smooth muscles in their walls. 21  Grade 8 Unit 14: Digestive System Ingestion involves the exposure of food to the saliva and its physical breakdown. Propulsion involves the alternating contraction of smooth muscles to push food along the gastrointestinal tract. c. Enumerate the structures involved and briefly describe the digestion of food in the digestive tract. Answer: The structures involved in both mechanical and chemical digestion are the mouth, stomach, and small intestine, as well as the accessory organs. In the mouth, both mechanical (through chewing) and chemical (through the amylase) digestion take place. In the stomach, the food is exposed to the gastric acid and pepsin for protein digestion. In the small intestine, the food is further digested upon exposure to the pancreatic juice and bile. d. Compare and contrast absorption with assimilation. Answer: Both processes are most closely associated with the small intestine. Absorption is the process wherein the digested food molecules are absorbed by the capillaries (for carbohydrates and amino acids) and lacteals (for fatty acids). 22  Grade 8 Unit 14: Digestive System Performance Assessment Use the following activities to assess performance. Ask the students to answer the following items in their notebooks. It will be graded and recorded thereafter. Determine the accuracy of each of I. the following statements. Write true if the statement is correct and false if otherwise. 1. Salivary secretions are increased as the food is being tasted. Answer: true 2. The process of grinding the food by the teeth is called deglutition. Answer: false 3. Humans have gut microbes that produce cellulase to aid in cellulose digestion. Answer: false 4. The act of swallowing is a voluntary type of propulsion. Answer: true 5. Peristalsis in the esophageal region, just like swallowing, requires conscious control. Answer: false 6. Segmentation of the small intestine also aids in the mechanical digestion of food. Answer: true 7. The presence of food in the stomach stimulates the production of the hormone secretin, that in turn stimulates the stomach cells to produce more gastric juice. Answer: false 8. The stomach also absorbs some of the water, minerals, and alcohol. Answer: true 9. The fatty acids from large fat molecules are absorbed into the lacteals alongside amino acids. Answer: False 10. A defecation reflex is being signaled as the undigested food fills the rectum. Answer: True Use the Check Your Understanding section in the study guide. Students II. may answer it in their notebooks and will be checked and graded 23  Grade 8 Unit 14: Digestive System afterward. Choose only selected items if not possible due to time constraints. A. Identify whether each of the cases given involved ingestion, propulsion, digestion, assimilation, absorption, and excretion. 1. Food is broken down into their building blocks through chemical means. Answer: Digestion 2. Fatty acids accumulate in the cells to form fats, proteins, and polysaccharides. Answer: Assimilation 3. Food is being swallowed and taken in by the mouth. Answer: Ingestion 4. Mixing of food with digestive juices is a process called churning. Answer: Digestion 5. Segmentation helps food to mix with digestive juices to prepare the food for further degradation. Answer: Digestion 6. Swallowing pushes the food from the mouth into the esophagus. Answer: Propulsion 7. Saliva breaks down carbohydrates in the food. Answer: Ingestion or digestion 8. Food particles are absorbed and transported into the bloodstream. Answer: Absorption 9. Movements in the large intestine move feces into the rectum. Answer: Excretion 10. The stomach performs peristalsis by relaxing its upper portion to accept food from the esophagus. Answer: Propulsion B. Identify the term being referred to in each statement. 1. Slow and long contractions in the large intestine. Answer: mass movements 2. Lymphatic vessels that absorb fatty acids and glycerol. Answer: lacteals 3. Fingerlike projections in the small intestine that increase surface area for absorption. Answer: villi 4. The hormone that signals the stomach to produce pepsinogen, mucus, and acids. Answer: gastrin 24  Grade 8 Unit 14: Digestive System 5. An enzyme in saliva that breaks down starch. Answer: amylase IV. Additional worksheets during class when time permits or after class. Recall Worksheet 10-item identification quiz (Level 1) Appendix A1. Assess-Recall Worksheet Comprehension Worksheet 10-points short-response essay (Level 2) Appendix A2. Assess-Comprehension Worksheet Application Worksheet 10-points short-response essay (Level 3) Appendix A3. Assess-Application Worksheet Synthesis Use the following strategies to end the session. 1. Summarize the lesson by asking the following core questions. a. What are the different events that take place in the digestive system? Answer: The different events that take place in the digestive system are ingestion, propulsion, digestion, absorption, assimilation, and excretion. b. How does the digestive system perform the digestion of food? Answer: The digestive system performs both mechanical and chemical digestion. Mechanical digestion is performed by mastication, churning in the stomach, and segmentation in the small intestine. Chemical digestion is performed by the action of the enzymes and other secretions of the salivary glands, stomach and intestinal walls, pancreas, and liver. c. How does the digestive system absorb digested food materials? Answer: The resulting monosaccharides and amino acids are moved into the capillaries and into the bloodstream. The fatty acids are absorbed through the lacteals. d. Why is excretion important? Answer: The fecal matter, when accumulated in the large intestine and rectum, may become toxic if not eliminated. 2. You may provide the following trivia about the structure of the digestive system. 25  Grade 8 Unit 14: Digestive System a. You can eat upside down. The food you eat does not require gravity for it to reach the stomach. The contractions of the smooth muscles in the walls of the esophagus allows the food to be pushed. In addition, the sphincters prevent backflow of the food from one compartment to the previous one. b. There is a close association between the functioning of the brain and the stomach. Thus, emotions (such as stress) and other brain disorders may affect the digestion process. 3. Remind the students to accomplish the following as homework. a. Reminder to bring the materials needed for the next warm-up activity. b. Perform advanced reading about the interaction of the digestive system with the other organ systems. c. Perform research about the causes and symptoms of lactose intolerance. 26  Grade 8 Unit 14: Digestive System Bibliography Bill W. Tillery, et al. 2010. Integrated Science, 4th edition. New York: McGraw-Hill. Earth Science. USA: CK-12 Foundation, 2009. Campbell, Neil A. and Jane B. Reece.. Biology, 6th edition. Singapore: Pearson Education South Asia Pte Ltd, 2004. Cecie Starr et al. BIOLOGY: Today and Tomorrow, 4th edition. Singapore: Cengage Learning Pte Ltd, 2014 Dee Thompson. SeattlePI Education. 2018. http://education.seattlepi.com/digestive-system-experiments-seventh-graders-6613. html Kelly Ludwig. Lincoln Way High School. 2018. http://mypages.iit.edu/~smile/bi9706.html Neil Campbell, et al. Biology, 10th edition. Singapore: Pearson Education South Asia Pte Ltd, 2013. 27  Grade 8 Unit 14: Digestive System Appendix A1. Recall Worksheet (with Answer Key) Identification. Determine the organ or area of the digestive system where each of the following events or processes takes place (10 points). 1. Mass movements involving slow and long contractions. Answer: stomach 2. Absorption of fatty acids through the lacteals. Answer: small intestine 3. Majority of the absorption of water and vitamins. Answer: large intestine 4. Release of the gastric juice which contains mucus, HCl, and pepsinogen. Answer: stomach 5. Release site of the pancreatic juice and bile. Answer: small intestine 6. Peristaltic action to prevent the food from refluxing into the mouth. Answer: esophagus 7. Grinding and cutting of food. Answer: mouth 8. Initiation of the chemical digestion of starch. Answer: mouth 9. Majority of the breakdown of carbohydrates into monosaccharides and of proteins into amino acids. Answer: small intestine 10. Elimination of undigested food material. Answer: anus 28  Grade 8 Unit 14: Digestive System Appendix A2. Comprehension Worksheet (with Answer Key) Short-Response Essay. Provide concise and accurate answers to the following questions. 1. How is the food propelled in the gastrointestinal tract (5 points)? Answer: After swallowing the food, the smooth muscles in the walls of the esophagus alternately contract and relax to allow the food to be pushed further. 2. How are digested food molecules absorbed by the body (5 points)? Answer: The digested carbohydrates and proteins in the form of monosaccharides and amino acids respectively are absorbed via the capillaries. The fatty acids from large fat molecules are absorbed via the lacteals. 29  Grade 8 Unit 14: Digestive System Appendix A3. Application Worksheet (with Answer Key) Short-Response Essay. Provide concise and accurate answers to the following questions. 1. If the small intestine will have an inner wall similar to that of the esophagus, what do you think will happen (5 points)? Answer: The small intestine has extensive folds in its inner wall in the form of villi and microvilli, that is not present in the esophagus. If these folds will not be present in the small intestine, the rate of absorption of the digested food particles will be slower. 2. What do you think will happen if the mucus production in the stomach suddenly becomes impaired (5 points)? Answer: Mucus protects the inner wall of the stomach from the hydrochloric acid that its cells produce. If the mucus lining becomes depleted, the stomach wall might be exposed and wounded by the acid. 30