Section 38.2 The Digestive System pp. 978 – 984

Why do we need to digest our food? What is digestion? Digestion is when our body converts food into simpler molecules (monomers). Why do we need to digest our food? Makes absorption of nutrients easier. Makes it easier for our cells to use the nutrients

There are 2 Kinds of Digestion MECHANICAL DIGESTION PURPOSE: Break the food into smaller pieces (a physical change) PROCESS: Chewing, churning, and mixing PLACE: In the mouth and stomach ONLY CHEMICAL DIGESTION PURPOSE: Breaks the food into it’s monomers (a chemical change) PROCESS: Enzymes and other compounds change the form of the food by chemical reactions PLACE: In the mouth, stomach, and small intestines ONLY

Stop #1 Mouth FUNCTION: PROCESS MECHANICAL: Chew and mix the food CHEMICAL: Break down starches (carbohydrates) PROCESS Teeth chew and mix the food Enzyme called AMYLASE from the salivary glands breaks starches down into sugars

Stop #2 the Esophagus FUNCTION: Moves food from the mouth to the stomach. PROCESS: Muscular contractions move the food down the the esophagus.

Stop #3 the Stomach FUNCTION: PROCESS MECHANICAL: Churn and mix the food CHEMICAL: Break down proteins PROCESS Muscles churn and mix the food Enzyme called PEPSIN is released from stomach cells to digest proteins into amino acids. Hydrochloric acid helps pepsin to function properly.

Stop #4 the Small Intestines FUNCTION: CHEMICAL: Break down proteins, carbohydrates and lipids ABSORPTION of nutrients PROCESS Enzymes are released from the small intestine, pancreas, and liver to aid in digestions of ALL nutrients Villi are small folded projections in the small intestines that allow for more surface area for nutrient absorption

Accessory Organs to Digestion Pancreas FUNCTION: Makes enzymes for digestion carbohydrates, lipids, and proteins PROCESS: Releases enzymes into the small intestine for digestion Liver/Gall Bladder FUNCTION: Makes bile for digestion of lipids PROCESS: Bile is made in the liver and stored in the gall bladder. The gall bladder releases bile into the small intestines for digestion

Stop #5 the Large Intestine FUNCTION: ABSORPTION of water ELIMINATION of remaining material PROCESS Water is absorbed through the walls of the large intestine. Muscle contractions compact and eliminate the remaining material

Table of Nutrient Digestion and Organs Chemical Digestion Mechanical Digestion Mouth Starches with amylase from saliva Chewing Esophagus NO Stomach Proteins with hydrochloric acid (HCl) and pepsin Churning Small Intestines Carbs, proteins, and fats with enzymes from the pancreas; fats with bile from liver Large intestines