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Nutrients… • substances in food that provide energy and materials for cell development, growth, and repair. Classes of Nutrient - Organic Carbohydrates: main source of energy Proteins: used for growth. Fats: provide energy (stored) helps body absorb vitamins Vitamins: organic nutrients that help your body to use other nutrients. Classes of Nutrients - Inorganic Minerals: Inorganic nutrients that regulate many chemical reactions Water: Enables chemical reactions to take place in your cells. Enzymes - Review speed up the rate of chemical reactions They do this without being changed or used up. speed up reactions by reducing amount of energy necessary for a chemical change to begin. Digestive Enzymes AMYLASE secreted in the mouth; breaks down carbohydrates (starches). PEPSIN, found in the stomach, breaks down proteins. Lipase made in pancreas; breaks down fats Additional Chemical Digestives • Gastric Juice – found in stomach; very acidic; (3 million times more acidic than your bloodstream) a combination of HCL and Pepsin; breaks proteins • Bile – made in liver; first process in breaking fats. Digestion Processes • Chemical: chemicals in the body break large molecules into smaller ones • Mechanical: physical, using teeth or muscle to help break food down The Alimentary Canal Mouth - chemical digestion • glands in mouth produce saliva, which contains amylase, which breaks down starch Mouth • Mechanical Digestion: – Teeth and tongue break food into smaller pieces Digestive System Esophagus: muscular tube connects throat to stomach. Moves food down by squeezing (peristalsis) Peristalsis • Rhythmic contraction of esophagus to move food to stomach. • https://www.youtube.com/watch?v=rJS-Kh5wCQU Your Digestive System Stomach: muscular bag Chemical Digestion: pepsin; gastric acid Mechanical Digestion: stomach contractions; food stays here ~2-6 hours, End Product: chyme: afood sludge Digestive System Liver: produces bile; stored in gallbladder. Bile breaks up large particles of fats into smaller particles. Some of Liver’s Jobs • • • • filters the blood coming from the digestive tract detoxifies chemicals and metabolizes drugs. secretes bile (breaks down fats) makes proteins important for blood clotting Your Digestive System Gall Bladder: small sac that stores bile produced by liver (breaks down fats) Your Digestive System Pancreas: • produces substances that stop the action of stomach acid • produces lipase which breaks fats Pancreas’ Other Jobs • excretes enzymes to break down the proteins, lipids, carbohydrates, and nucleic acids in food. • as an endocrine gland, secretes the hormones insulin and glucagon to control blood sugar levels throughout the day. Digestive System Small Intestine: digestive juices from liver and pancreas are added villi increase surface area for absorption of nutritents from chyme Villi Small Intestines • absorbs about 90% of the nutrients from the food we eat. • only 1 inch in diameter, making it less than half the diameter of the large intestine. https://www.youtube.com/watch?v=CFjlRhs1 rR8 3 Parts of Small Intestine - FYI • duodenum – connects to the pyloric sphincter of the stomach. • Partially digested food, or chyme, from the stomach is mixed with bile from the liver and pancreatic juice from the pancreas to complete its digestion in the duodenum. 3 Parts of Small Intestine - FYI • The jejunum is the middle section; primary site of nutrient absorption • The ileum is the final section and completes the absorption of nutrients that were missed in the jejunum. Digestive System • Large Intestine: absorbs (removes) water from undigested food; – unabsorbed materials become more solid (waste - poop). Your Digestive System Rectum: where muscles control the release of wastes from the body https://www.youtube.com/watch?v=Ujr0UAbyPS4 The Human Digestive System http://www.dnatube.com/vi deo/8362/DigestiveSystem-Animation