Chapter Two Food and Digestion
I. The Digestive Process Begins A. Functions- 1. Digestion: The process by which your body breaks down food into small nutrient molecules. (mechanical and chemical)
2. Absorption: The process by which nutrient molecules pass through the wall of your digestive system into your blood.
3. Elimination: Materials that are not absorbed are eliminated from the body as waste (ie. Fiber)
Diagram of Digestive System Page 61
B. Mouth • Saliva: Fluid released when your mouth waters and plays an important part in both mechanical and chemical digestion. Types of Digestion • Mechanical Digestion- Teeth begin digestion by cutting, tearing, and grinding food
3. Chemical Digestion: • Chemical in saliva breaks down the food into smaller building blocks • Enzymes: • Proteins that speed up chemical reactions in the body (page 63)
C. Esophagus- Total Time 10 seconds. 1. 1. Epiglottis: Flap of tissue that seals off your windpipe preventing food from entering. 2. Esophagus: Food enters a muscular tube that connects the mouth to the stomach. 3. Mucus: Thick, slippery substance that lines the esophagus in order to make food easier to swallow and move along
4. Peristalsis Involuntary waves of muscle contractions, keep food moving in one direction.
D. Stomach (Total Time- Few Hours) J-shaped muscular pouch located in the abdomen.
Mechanical Digestion: Three strong layers of smooth muscle contract to produce a churning motion. (similar to a washing machine) • 2. Chemical Digestion: Churning food makes contact with digestive juices. • a. Enzyme Pepsin- Works best in an acid environment. • b. b. Hydrochloric Acid (HCl).-Kills many bacteria that you swallow with food, mucus protects stomach lining from this acid. • c. Food remains in the stomach until the entire solid has been broken down.
II. Final Digestion and Absorption • Small Intestines: • Part of the digestive system where almost all chemical digestion and absorption of nutrients takes place. 6 Meters in length, 2-3 cm wide
Located in upper right portion of the abdomen and produces bile to break down medicines and help eliminate nitrogen Liver
a. Bile: Breaks down the fat particles to increase their surface area and flows from the liver into the gallbladder b. Gallbladder: The organ that stores bile 2. Pancreas: Triangular organ that lies between the stomach and the small intestines. Produces enzymes that flow into the small intestines and help to breakdown starches, proteins, and fats.
3. Absorption in the Small Intestine • Villi: • Fingerlike structures increase the surface area of the small intestines and allow nutrient molecules to pass into the blood
B. The Large Intestine -The last section of the digestive system that contain bacteria that feed on material and make vitamins (1.5 meters long) -The role is absorb water into the bloodstream and get remaining material ready for elimination.
1. 1. Rectum: The end of the Large Intestines where waste is compressed into a solid form 2. Anus: The muscular opening at the end of the rectum where waste material is eliminated THE END