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Body Systems The Digestive System The Basics • We all need energy to live • We get it from different sources – Carbohydrates (sugars/starches) – Lipids (fats/oils) – Proteins (meat/lentils/beans) • The Digestive system takes these sources and makes them useable to the body Types of Digestion • Two Types… • Mechanical: physical breakdown of food – Chewing/mixing – Teeth/jaw & tongue • Chemical: breaking down large particles into smaller particles using enzymes Teeth – Cool Photo Step 1: Mouth & Esophagus • Food enters our body through our mouth • We chew and grind it down • It also mixes with saliva which comes from 3 different saliva glands • They release the Why is saliva important? enzyme amylase • Starch molecules into sugar molecules Aside - Carbohydrates • Why are they important? What do they do? – They are the main fuel source for our body – The energy that gets used first – Recommended that 45-60% is carbohydrates • Where do they come from? – Vegetables, grains, low-fat dairy, fruits Step 1: Mouth & Esophagus • When ready to swallow food tongue pushes the food back • Flap of skin called epiglottis moves across your windpipe • Into the esophagus it goes • It is pushed down your throat by the muscles that line the esophagus … this is peristalsis – Chewed food is known as bolus – Swallowing is known as delutition Esophagus Swallowing Video Step 2: The Stomach • A little history … • • • • • Alexis St. Martin & Dr. William Beaumont Alexis had big wound in his left side Could not be repaired entirely What did they do? As if you are Dr. Beaumont put food on a string and letting dangled it into the stomach to see what me do this! Lol! happened – lol science history! Step 2: The Stomach - Cont Step 2: The Stomach • Food enters the stomach through a sphincter (esophageal) • Muscular wall of the stomach mixes it around with the gastric juices • What is that? – Water – Mucus – Hydrochloric Acid – Digestive Enzymes Step 2: The Stomach • The acid, enzymes and water liquefy the food and break it down chemically • It passes into the small intestine through another sphincter (pyloric) • Why do we need mucus in the stomach? – So acid does not burn a hole thru the stomach! – The acid in the stomach is hydrochloric acid Acid Video Step 2: The Stomach Step 3: Gastrointestinal Tract • The pancreas, a large gland in the back of the stomach, helps break down food, sends digestive enzymes into the small intestine • Enzymes complete the breakdown of starches and proteins into small particles which are more easily absorbed by the body Step 3: Gastrointestinal Tract Step 3: Gastrointestinal Tract • The liver produces a substance called bile (which is stored in the gall bladder) • The gall bladder sends bile into the small intestine, where it breaks up large amounts of lipids into small drops Step 3: Gastrointestinal Tract • When food is broken down into smaller particles, the small intestine absorbs these particles. • The inner surface of the small intestine contains villi (small, finger like objects) – Villi increases the surface area of the intestine to help absorb nutrients. – Villi is covered with epithelial tissue & food molecules get absorbed by this tissue. Bacteria … Can Be Good? Step 4 – The End of the Road • Food then passes from the small intestine to the large intestine • Key part here is that water is absorbed in the large intestine • When it hits the end of the road … washroom break! Summary Video Digestive System