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Objective: You will be able to identify the structures of the digestive system. Do Now: • Read all of page 978 • Give the function of the digestive system Figure 41.12 The four stages of food processing Small molecules Pieces of food Mechanical digestion Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Undigested material Food 1 INGESTION 2 DIGESTION 3 ABSORPTION 4 ELIMINATION Purpose of Digestive System • Food is moved along a tube by muscular contractions. • Food never actually enters body tissues until it is broken down • The food has to be small enough to diffuse through the cell membrane • Remember the State Diffusion lab? Figure 41.13 The human digestive system Objective: You will be able to provide the functions of each digestive organ. Do Now: • Read “The Stomach” which includes “chemical digestion” on p. 980 • List the 2 chemicals released into the stomach • What organic compound begins its digestions here in the stomach? Oral Cavity • Mechanical digestion breaks food into smaller pieces – Increases surface area for chemical digestion • Chemical digestion of starch occurs here – Done by salivary amylase – NOTE: Carbohydrate digestion begins here Esophagus • No digestion occurs here • It moves food from oral cavity to stomach by using muscles • Called peristalsis Stomach • Mechanical digestion occurs by the grinding of the stomach’s muscles • Chemical digestion of proteins begins here Liver Bile Gallbladder Stomach Acid chyme Intestinal juice Pancreatic juice Pancreas Duodenum of small intestine Small Intestine • Most of the chemical digestion occurs here – Intestinal glands and the accessory organs help to digest food • Liver, gall bladder and pancreas • All of the absorption of food into the body occurs here • No food is digested AFTER it leaves the small intestine Liver Bile Gallbladder Stomach Acid chyme Intestinal juice Pancreatic juice Pancreas Duodenum of small intestine Accessory organs • The liver makes the bile but it stores it in the gall bladder • It’s the gall bladder that actually secretes bile into the small intestine – Bile emulsifies fats (breaks them down) • The pancreas secretes digestive enzymes Liver Bile Gallbladder Stomach Acid chyme Intestinal juice Pancreatic juice Pancreas Duodenum of small intestine Large Intestine • This organs main function is to absorb water • It does NOT absorb food nor does it digest food!!!! End of the line • Strong peristaltic action from the rectum pushes waste out of the anus Objective: You will be able to explain how the digestive system is similar to organelles found within cells. Do Now: – Take out the frog dissection lab from yesterday. – Begin to finish answering the questions on the lab Villi increase the surface for more food absorption. • Which organelle(s) in a cell carry out similar function to the following organs: – Stomach – Small Intestine – Rectum – Anus Chemical Digestion • Carbohydrates Simple sugars (Glucose) • Proteins Amino Acids • Nucleic Acids (DNA) Nucleotides (A, G, C, T) Objective: You will be able to provide the functions of each digestive organ. Do Now: • Read “Absorption in the Small Intestine” on p. 982-983 • Describe the structure of the villi • Where does food go that gets absorbed by the villi? Group Roles • Leader – keeps the group focused and on task • Recorder – Writes down the work for the group • Reporter – Informs the class/teacher about the work done by the group • Noise monitor – Makes sure that the group works quietly Activity • Create story about the digestive canal of horrors where a group of teenage worm friends enter a tunnel but end up being digested by enzymes • Remember that only some of the carbohydrate and protein digestion happens outside intestines • Be sure to include each structure and describe in full detail what they do. Figure 41.13 The human digestive system