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Parts of the digestive system (draw the missing pictures) HBS pgs. 30 - 31 Esophagus HBS pgs. 30 - 31 Stomach In Joann’s mouth, her teeth begin to mechanically digest the slice of pizza. (Mechanical digestion increases the surface area of the food thus allowing the digestive enzymes/juices greater access to the food pieces in order to more efficiently do their job.) At the same time, her tongue is mixing the food with her saliva which is produced by her three pairs of salivary glands. In her saliva there is an enzyme called amylase that begins the chemical digestion of starches (complex carbohydrates). The starches are broken down into simple sugars. Digestive enzymes help the body chemically break down nutrients into forms that the body can use. The ball of soggy food is now called a bolus as it travels down the food tube, the esophagus. To make sure that the bolus only travels down the esophagus and not the windpipe (which leads to the lungs), the epiglottis (flap of skin) will shut off the entrance to the windpipe making sure food does not end up in your lungs. The food moves down our esophagus as a result of regular wave-like muscular contractions called peristalsis which moves food through the entire digestive tract. At the end of the esophagus is the lower esophageal sphincter, a tight ring of muscles that make sure the food stays in the stomach and moves in a one-way direction. Peppi and Bollo find themselves in the J-shaped organ known as the stomach. The stomach has folds of pink velvet and a lot of gastric juice which is a digestive juice made up of hydrochloric acid and an enzyme called pepsin. Here begins the chemical digestion of proteins. The churning of the stomach helps the gastric juices do their job even better. The churning is caused by the 3 layers of muscles that make up the stomach wall. This churning is an example of mechanical digestion. The thick, creamy contents of the food in the stomach is called chyme. The stomach is coated with a thick layer of mucus to protect it from the gastric juice, but if the juice finds a spot without mucus, it can penetrate the stomach and make a small hole known as an ulcer. And when the gastric juice backs up into the lower esophagus from the stomach, you get a burning sensation which is called heartburn but it has nothing to do with your heart. Vomiting can be triggered by bad food, by some medications, or by poisons. Teeth / Tongue Bolus / Saliva Amylase / Enzyme Mechanical Digestion Chemical Digestion Sugar/Starch Sphincter / Peristalsis Salivary Glands Esophagus / Windpipe Epiglottis Gastric Juices Hydrochloric Acid Enzyme / Pepsin Protein Stomach Muscles Chyme Mucus / Ulcer Heartburn Mechanical (muscles churning) & Chemical (gastric juice) HBS pgs. 38 -39 What does it do? Mechanical (teeth and tongue) Nothing significant. & Chemical (amylase) Mouth Words to include in your description. Type of digestion: mechanical or chemical Digestive System Grid – Teacher Version Pancreas Liver Gall Bladder Large intestine Duodenum Pancreatic Juices Bile Protein / Amino Acids Carbohydrates Fats Surface Area Bloodstream Villi / Microvilli Colon Appendix Appendicitis Water / Minerals Bloodstream Waste / Feces / Gas Diarrhea / Constipation (peristalsis) HBS pg. 56 – 59 Peppi and Bollo enter the large intestine which is also called the colon. Just off to the right is the entrance to the appendix which scientists believe has no known function but can get infected and cause appendicitis. As they move through the large intestine, more and more of the water is being absorbed out of the waste. No food is digested here, it’s just waste (feces). Both minerals and water are absorbed out into the bloodstream to help keep the body in balance. (There are also some vitamins which are made in the large intestine!) Two things can go wrong in the large intestine: if the waste moves too quickly, and not enough water is absorbed out…diarrhea. If the waste moves too slowly and a lot of water is absorbed out…constipation. To prevent constipation, eat more fiber or take a laxative. Bacteria in the large intestine start to fed on undigested food and can release gas. Pyloric Sphincter Mechanical (peristalsis) HBS pgs. 48 – 49, 54 – 55 Leaving the stomach, Peppi and Bollo pass through the pyloric sphincter which leads them to the first 25 cm of the small intestine, better known as the duodenum. Into the duodenum the pancreas squirts pancreatic juice which is packed with enzymes that help chemically digest carbs, proteins and fats. The gall bladder also squirts in the greenish-yellow liquid called bile that the liver produced. (The bile mechanically digests the fats, turning it into smaller fat droplets. This is similar to what dish detergent does!) The pancreatic juice is alkaline, or basic, to neutralize the stomach acids. At this point, proteins chemically break down further into amino acids, complex carbs into simple sugars, and fats into fatty acids and glycerol. The chemical digestion is now complete and the particles are now simple enough to be absorbed through the lining of the small intestine. Your digestive system has ways of making sure the surface area of the food you eat is as large as possible. Chewing begins to increase the surface area of food, allowing digestive enzymes greater access to them. As the chyme moves through the small intestine, the nutrients are absorbed through the intestinal wall into your bloodstream. The intestinal wall is packed with wrinkles and folds which are covered with tiny projections called villi and the villi are covered with even small microvilli. The folds, villi and microvilli are yet another way that the digestive system increases the surface area to maximize nutrient absorption! Chemical (bile & pancreatic juice) Small intestine