+ Digestion

+ Video: Magic School Bus

+ The Masher Mouth

+ Seeing or smelling food can start saliva flowing in mouth saliva starts to break down food chemically & adds water Carbs can be broken down into simple sugars by maltase and amylase (enzymes) Chewing and grinding teeth can physically break down food (mastication) Tongue pushes food to back of mouth where epiglottis is located Epiglottis closes trachea (tube to lungs), stopping food from going down trachea and instead forcing food down the esophagus

+ The Passage Esophagus

+ Tube-like passage carries food from the mouth to the stomach Coated with a membrane lining that secretes mucus (protect against acid, foods not thoroughly chewed, etc.) Food broken down into smaller particles through the esophagus by peristalsis (waves of muscular contractions)

+ The Churner Stomach

+ Grind and churns food and mixes it with acid and enzymes (forming chyme) Comfortable capacity is 1-2 L, can stretch 3-4 L Cells lining the stomach secrete gastric juice that contains: Mucus – Protects stomach from enzymes and acid Hydrochloric acid – Creates a high acid environment which aids helps pepsin and prevents harmful bacterial growth Pepsin is the only enzyme that can break down collagen (a protein and major component of meat) Enzymes – Begin digestion of protein and fat (ex. pepsin, gastric lipase) Gastrin – Hormone made by body and controls acid secretion

+ The Absorber Small intestine

+ Small intestines Has three sections: duodenum, jejunum and ilium Duodenum is the first part of small intestines, receives enzymes from pancreas and bile from liver to continue digestion Enzymes are necessary to break down carbs and protein Most absorption happen in the jejunum and ilium: lining is specially designed to create the greatest possible surface area for nutrient absorption By end of small intestines, mostly water, dissolved minerals and indigestible fibre remain All nutrients that are absorbed through the small intestines are filtered through the liver

+ The Poop Maker Large intestine

+ Includes cecum, appendix, colon and rectum Food (chyme) passes through large intestine by peristalsis Body absorbs water and vitamins (some bacteria in the colon actually produce vitamins)

+ Important organs that are not a part of the digestive tract

+ The Filter Liver

+ Nutrients that are absorbed through the intestinal walls enter veins and are filtered through the liver Removes bacteria and foreign particles Manufactures half of the body’s cholesterol Cholesterol is then used to create bile (a greenish liquid that helps the body digest and absorb fat)

+ The Producer Pancreas

+ Produces digestive enzymes and hormones Digestive enzymes are released into the duodenum (small intestines) and hormones into the bloodstream Insulin is a hormone produced by the pancreas Insulin reduces blood sugar by moving sugar (glucose) into cells

+ The Holding Tank Gallbladder

+ Stores bile When food enters into the duodenum, it signals to the gallbladder to release bile Bile: Helps to breakdown cholesterol, fats, fat-soluble vitamins Drugs and other waste products are excreted in bile Bile salts are absorbed at the end of the small intestines and recirculate

+ Video: What causes constipation?

+ Video: How digestion works

+ Video: Why do I have gas?

+ How long does it take to process a complete meal? 24 hours 4 hours in stomach 6 hours in small intestine remaining 14 hours in large intestine

+ Nutrient Digestion NutrientMouthStomachSmall IntestineLarge Intestine Water← Added → ← Reabsorbed → Carbohydrates ← Breakdown by enzymes → ←Most absorbed→ ← Remaining broken Down by bacteria→ Proteins ← Breakdown by enzymes → ←Most absorbed→ Fats ← Breakdown by enyzmes → ←Emulsified by bile→ ←Most absorbed→ Vitamins ←Most absorbed→ Minerals ←Most absorbed→←Some salts absorbed with water→ Dietary Fibre (non-nutritive ← Collected for excretion →