1. Final Digestion and Absorption
Chapter 15
Section 3

2. Key Concepts
What 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 intestine
Rectum
Anus

4. The stomach
The 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 Intestine
After the liquid leaves the stomach it enters the small intestine
It is 6 meters long, and makes up two thirds of the length of the digestive system
It is approx. 2-3 centimeters wide
Mechanical 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 all
Almost all chemical digestion and absorption of nutrients takes place in the small intestine
As it moves into the small intestine it mixes with enzymes and secretions that are produced by the small intestine, the liver and the pancreas
Small tubes deliver this substance

7. Liver Largest organ in the body
Breaks down such things as medicine’s and helps eliminate nitrogen from the body
Produces bile
Bile physically breaks up large fat particles into smaller fat droplets
Ex. 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. Pancreas
Produces enzymes that flow into the small intestine and help break down starches, proteins and fats
Digestive enzymes do not break down all food substances
Ex -fiber in food isn’t broken down
Instead 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 body
The inner surface or lining of the small intestine looks bumpy-villi (tiny finger shaped structures) cover the surface
Villi 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 vessels
Blood carries the nutrients throughout the body for use by body cells
If all the villi were laid out the total surface area of the small intestine would be about as large as a tennis court
The 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 side
Contains 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 bloodstream
Remaining material is reading for elimination from the body
Large intestine ends in the rectum
Waste material is compressed into a solid form
The 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?
Absorption
Most 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 particles
Pancreas 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 digestion
absorption

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