Final Digestion and Final Digestion and AbsorptionAbsorption

Chapter 15Chapter 15

Section 3Section 3

Key ConceptsKey Concepts

What digestive processes occur What digestive processes occur in the small intestine, and how in the small intestine, and how are other digestive organs are other digestive organs involved?involved?

What role does the large What role does the large intestine play in digestion?intestine play in digestion?

Key TermsKey Terms

Small intestineSmall intestine LiverLiver

Bile Bile GallbladderGallbladder

PancreasPancreas VillusVillus

Large intestineLarge intestine RectumRectum

AnusAnus

The stomachThe stomach

The stomach can be thought of as The stomach can be thought of as the “ticket taker” of the digestive the “ticket taker” of the digestive system.system.

Once the food has been changed Once the food has been changed into a thick liquid, the stomach into a thick liquid, the stomach releases a little of the liquid into the releases a little of the liquid into the next part of the digestive system. next part of the digestive system. The slow smooth passage of liquid The slow smooth passage of liquid ensures digestion and absorption ensures digestion and absorption can take place efficientlycan take place efficiently

Small IntestineSmall Intestine

After the liquid leaves the stomach it After the liquid leaves the stomach it enters the small intestineenters the small intestine

It is 6 meters long, and makes up It is 6 meters long, and makes up two thirds of the length of the two thirds of the length of the digestive systemdigestive system

It is approx. 2-3 centimeters wideIt is approx. 2-3 centimeters wide Mechanical digestion is complete Mechanical digestion is complete

and chemical digestion has just and chemical digestion has just begunbegun

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Starches and proteins have been Starches and proteins have been partially broken downpartially broken down

Fats haven’t yet been digested at allFats haven’t yet been digested at all Almost all chemical digestion and Almost all chemical digestion and

absorption of nutrients takes place in absorption of nutrients takes place in the small intestinethe small intestine

As it moves into the small intestine it As it moves into the small intestine it mixes with enzymes and secretions mixes with enzymes and secretions that are produced by the small that are produced by the small intestine, the liver and the pancreasintestine, the liver and the pancreas

Small tubes deliver this substanceSmall tubes deliver this substance

LiverLiver

Largest organ in the bodyLargest organ in the body Breaks down such things as medicine’s Breaks down such things as medicine’s

and helps eliminate nitrogen from the bodyand helps eliminate nitrogen from the body Produces bileProduces bile Bile physically breaks up large fat particles Bile physically breaks up large fat particles

into smaller fat dropletsinto smaller fat droplets Ex. Soap breaks up grease into small droplets Ex. Soap breaks up grease into small droplets

that can mix with soapy water and be washed that can mix with soapy water and be washed away. Bile mixes with the fats in food to form away. Bile mixes with the fats in food to form small droplets. Droplets can then be chemically small droplets. Droplets can then be chemically broken down by enzymes produced in the broken down by enzymes produced in the pancreas.pancreas.

PancreasPancreas

Produces enzymes that flow into Produces enzymes that flow into the small intestine and help the small intestine and help break down starches, proteins break down starches, proteins and fatsand fats

Digestive enzymes do not break Digestive enzymes do not break down all food substancesdown all food substances Ex -fiber in food isn’t broken downEx -fiber in food isn’t broken down

Instead fiber thickens the liquid Instead fiber thickens the liquid material in the intestine making it material in the intestine making it easier for peristalsis to take placeeasier for peristalsis to take place

Absorption in the small Absorption in the small intestineintestine

After chemical digestion, small After chemical digestion, small nutrient molecules are ready to nutrient molecules are ready to be absorbed by the bodybe absorbed by the body

The inner surface or lining of the The inner surface or lining of the small intestine looks bumpy-villi small intestine looks bumpy-villi (tiny finger shaped structures) (tiny finger shaped structures) cover the surfacecover the surface

Villi absorb nutrient moleculesVilli absorb nutrient molecules

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Tiny blood vessels run through the center Tiny blood vessels run through the center of each villusof each villus

Nutrient molecules pass from cells on the Nutrient molecules pass from cells on the surface of a villus into blood vesselssurface of a villus into blood vessels

Blood carries the nutrients throughout the Blood carries the nutrients throughout the body for use by body cellsbody for use by body cells

If all the villi were laid out the total surface If all the villi were laid out the total surface area of the small intestine would be about area of the small intestine would be about as large as a tennis courtas large as a tennis court

The increased surface enables digested The increased surface enables digested food to be absorbed much faster than if the food to be absorbed much faster than if the walls of the small intestine were smoothwalls of the small intestine were smooth

Large intestineLarge intestine

1.4 meters long-average size of a 1.4 meters long-average size of a bathtubbathtub

Runs up the right-hand side of the Runs up the right-hand side of the abdomen, across the upper abdomen, across the upper abdomen and then down the left abdomen and then down the left hand sidehand side

Contains bacteria that feed on the Contains bacteria that feed on the material passing through-they are material passing through-they are helpful bacteria they make certain helpful bacteria they make certain vitamins-ex vitamin Kvitamins-ex vitamin K

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Large intestine contains water and Large intestine contains water and undigested foodundigested food

As the material moves through the large As the material moves through the large intestine water is absorbed into the intestine water is absorbed into the bloodstreambloodstream

Remaining material is reading for Remaining material is reading for elimination from the bodyelimination from the body

Large intestine ends in the rectumLarge intestine ends in the rectum Waste material is compressed into a solid Waste material is compressed into a solid

formform The waste material is eliminated from the The waste material is eliminated from the

body through the anus at the end of rectumbody through the anus at the end of rectum

1. What are the functions of 1. What are the functions of the small intestine?the small intestine?

AbsorptionAbsorption Most chemical digestion takes Most chemical digestion takes

place hereplace here

2.Do foods pass through the 2.Do foods pass through the liver and pancreas? liver and pancreas?

nono

3. What is their role in 3. What is their role in digestion?digestion?

The liver produces bile that The liver produces bile that breaks up fat particlesbreaks up fat particles

Pancreas produces enzymes Pancreas produces enzymes that help break down starches, that help break down starches, proteins and fatsproteins and fats

4. What is the advantage of a 4. What is the advantage of a long small intestine?long small intestine?

The length provides more The length provides more surface on which nutrients are surface on which nutrients are digested and absorbed.digested and absorbed.

5. What structures are inside the 5. What structures are inside the single villus in the diagram?single villus in the diagram?

Blood vessels run through itBlood vessels run through it

6. How do nutrients from the 6. How do nutrients from the small intestine get to the rest small intestine get to the rest of the body?of the body?

They pass from the cells on the They pass from the cells on the villi into blood vesselsvilli into blood vessels

7. What two digestive 7. What two digestive processes occur in the small processes occur in the small intestine?intestine?

Chemical digestionChemical digestion absorptionabsorption

8. Which key nutrient is 8. Which key nutrient is absorbed in the large intestineabsorbed in the large intestine

waterwater

9. What happens as food 9. What happens as food moves through the large moves through the large intestineintestine

Water is absorbed into the Water is absorbed into the bloodstream and the remaining bloodstream and the remaining material is readied for material is readied for elimination from the bodyelimination from the body