Presentation on theme: "Final Digestion and Absorption"— Presentation transcript:
1 Final Digestion and Absorption Chapter 15Section 3
2 Key ConceptsWhat digestive processes occur in the small intestine, and how are other digestive organs involved?What role does the large intestine play in digestion?
3 Key Terms Small intestine Liver Bile Gallbladder Pancreas Villus Large intestineRectumAnus
4 The stomachThe stomach can be thought of as the “ticket taker” of the digestive system.Once the food has been changed into a thick liquid, the stomach releases a little of the liquid into the next part of the digestive system. The slow smooth passage of liquid ensures digestion and absorption can take place efficiently
5 Small IntestineAfter the liquid leaves the stomach it enters the small intestineIt is 6 meters long, and makes up two thirds of the length of the digestive systemIt is approx. 2-3 centimeters wideMechanical digestion is complete and chemical digestion has just begun
6 (2) Starches and proteins have been partially broken down Fats haven’t yet been digested at allAlmost all chemical digestion and absorption of nutrients takes place in the small intestineAs it moves into the small intestine it mixes with enzymes and secretions that are produced by the small intestine, the liver and the pancreasSmall tubes deliver this substance
7 Liver Largest organ in the body Breaks down such things as medicine’s and helps eliminate nitrogen from the bodyProduces bileBile physically breaks up large fat particles into smaller fat dropletsEx. Soap breaks up grease into small droplets that can mix with soapy water and be washed away. Bile mixes with the fats in food to form small droplets. Droplets can then be chemically broken down by enzymes produced in the pancreas.
8 PancreasProduces enzymes that flow into the small intestine and help break down starches, proteins and fatsDigestive enzymes do not break down all food substancesEx -fiber in food isn’t broken downInstead fiber thickens the liquid material in the intestine making it easier for peristalsis to take place
9 Absorption in the small intestine After chemical digestion, small nutrient molecules are ready to be absorbed by the bodyThe inner surface or lining of the small intestine looks bumpy-villi (tiny finger shaped structures) cover the surfaceVilli absorb nutrient molecules
10 (2) Tiny blood vessels run through the center of each villus Nutrient molecules pass from cells on the surface of a villus into blood vesselsBlood carries the nutrients throughout the body for use by body cellsIf all the villi were laid out the total surface area of the small intestine would be about as large as a tennis courtThe increased surface enables digested food to be absorbed much faster than if the walls of the small intestine were smooth
11 Large intestine 1.4 meters long-average size of a bathtub Runs up the right-hand side of the abdomen, across the upper abdomen and then down the left hand sideContains bacteria that feed on the material passing through-they are helpful bacteria they make certain vitamins-ex vitamin K
12 (2) Large intestine contains water and undigested food As the material moves through the large intestine water is absorbed into the bloodstreamRemaining material is reading for elimination from the bodyLarge intestine ends in the rectumWaste material is compressed into a solid formThe waste material is eliminated from the body through the anus at the end of rectum
13 1. What are the functions of the small intestine? AbsorptionMost chemical digestion takes place here
14 2.Do foods pass through the liver and pancreas? no
15 3. What is their role in digestion? The liver produces bile that breaks up fat particlesPancreas produces enzymes that help break down starches, proteins and fats
16 4. What is the advantage of a long small intestine? The length provides more surface on which nutrients are digested and absorbed.
17 5. What structures are inside the single villus in the diagram? Blood vessels run through it
18 6. How do nutrients from the small intestine get to the rest of the body? They pass from the cells on the villi into blood vessels
19 7. What two digestive processes occur in the small intestine? Chemical digestionabsorption
20 8. Which key nutrient is absorbed in the large intestine water
21 9. What happens as food moves through the large intestine Water is absorbed into the bloodstream and the remaining material is readied for elimination from the body