Digestion Chapter 3, Lesson 3 and 4

Brain Pop Digestion

Three Functions – p Digestion Your body breaks down food into small nutrient molecules

Three Functions – p types Mechanical – bits of food are torn or ground into smaller pieces Chemical – chemicals (enzymes) break down foods into nutrients

Functions (cont.) 2. Absorption Nutrient molecules pass through the walls of the digestive system into the blood Most absorption happens in the small intestines

Functions (cont.) 3. Elimination The large intestine eliminates materials that are not absorbed

Think Time Compare the digestive system to sink and garbage disposal work. Digestion: Absorption: Elimination:

The Mouth, Esophagus, and the Stomach – p. 82 Organs where mechanical digestion is completed and chemical digestion begins Mouth Once you bite off a piece of food, mechanical and chemical digestion begins Mechanical Digestion Teeth cut, tear, crush and grind food Tongue pushes food toward your teeth Chemical Digestion Saliva contains chemicals and moistens food

Think Time Complete the Diagram on Page 82

Roles (cont.) Esophagus – p. 84 Muscular tube connecting the mouth to the stomach As you swallow, epiglottis seals off windpipe and prevents food from entering in the lungs Food moves into esophagus after swallowing Lined with mucus to make food move easily Involuntary muscle contractions (peristalsis) pushes food toward stomach

Roles (cont.) Stomach p. 84 When food leaves the esophagus it enters the stomach Most mechanical and some chemical digestion Mechanical – smooth muscle contracts to produce churning motion; mixes the food with fluids Chemical – the churning food mixes with digestive juices (pepsin, hydrochloric acid) Food stays in stomach a few hours until mechanical digestion is complete

Think Time Complete the Sequence and Infer on page 84

The Small Intestine – p meters long and makes up two-thirds the length of the digestive system Only 2 to 3 centimeters in diameter Most of the chemical digestion and absorption of nutrients take place here Villi (finger-shaped structures) help increase the surface area Nutrients pass from cell on the surface of villi into blood vessels to be delivered to body cells

Think Time Complete the Diagram on Page 87 In Detail Box 1 Describe the role of the Small Intestine in Digestion In Detail Box 2 Describe the role of the Small Intestine in Absorption In Detail Box 3 Predict the role of the Small Intestine in Elimination

Liver and Gall Bladder – p. 88 Liver produces bile to break up fat particles The gall bladder stores the bile once it is made Bile is released when food enters the small intestine but does not aid in chemical digestion (breaks large fat particles into smaller ones)

Pancreas – p. 88 Located between the stomach and first part of the small intestine Produces digestive enzymes to break down carbohydrates, proteins and fats Enzymes are sent to small intestine to help with chemical digestion

Think Time Complete the Diagram on Page 88

Large Intestine – p. 90 Most nutrients have been absorbed by the end of the small intestine Water and undigested food moves from the small to large intestine (last section of the digestive system) As material moves through the large intestine, water is absorbed into blood stream and rest is prepared for elimination About 1.5 meters long

Large Intestine Contains bacteria to make certain vitamins from feeding on materials as they pass through Large intestine ends in a short tube called the rectum Waste material is eliminated through the anus

Think Time Complete the Diagram on Page 91