1. Section 10.1 Your Digestive System Objectives
Describe the three main functions of the digestive system.
Identify the organs of the digestive system and their functions.

2. Myth Food is digested in the stomach.
Fact Although protein digestion does begin in the stomach, most digestion occurs in the small intestine.
List three questions you have about how the digestive system functions. Look for the answers in the chapter.

3. Functions of the Digestive System
Your digestive system has three main functions
digestion
absorption
elimination

4. Digestion
The process by which the digestive system breaks down food into molecules that the body can use is called digestion.
During mechanical digestion, foods are physically broken apart into smaller pieces.
During chemical digestion, chemicals produced by your body break large molecules into smaller ones that your body can use.
Most of the chemicals involved in digestion are enzymes, substances that speed up reactions.

5. Absorption and Elimination
Absorption is the process by which nutrients pass through the lining of your digestive system into your blood.
Materials that are not absorbed are eliminated from the body as wastes.

6. For: More on the digestive system
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7. Structures of the Digestive System
The organs of the digestive system include the
mouth
pharynx
esophagus
stomach
small intestine
large intestine
liver
gallbladder
pancreas

8. Mouth Your teeth tear, crush, and grind your food.
Your tongue pushes the food around.
An enzyme in saliva begins to break down starches in your food.
Saliva moistens the bites of food.

9. Pharynx
The pharynx is the junction between the digestive tract and the respiratory system.
A flap of tissue called the epiglottis seals off the trachea, or windpipe, preventing food and liquid from entering your lungs.

10. Esophagus
After passing through the pharynx, the food enters the esophagus, a muscular tube that connects the pharynx to the stomach
Waves of muscle contractions, called peristalsis, push food through the rest of the digestive system.

11. Pharynx
Mouth
Epiglottis
Salivary gland
Esophagus
Liver
Stomach
Pancreas
Small intestine
Gallbladder
Large intestine
Rectum

12. Enzymes in Action
In this activity, you will observe the effect on enzymes on foods.
Materials
crackers • meat tenderizer • milk • orange juice
2 clear glasses • 2 stirrers
Chew a cracker for 5 seconds. Do not swallow it. Note how the cracker tastes.
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13. Enzymes in Action
Continue chewing the cracker for 5 minutes. Note how the taste of the cracker changes before swallowing it.
Place 2 tablespoons of milk into one glass. Place 2 tablespoons of orange juice into another glass.
Add 1 tablespoon of meat tenderizer to each glass. Stir well with separate stirrers.
After 30 minutes, look closely at the contents of the two glasses. Record your observations.

14. Enzymes in Action
Think and Discuss
How did the taste of the cracker change during the five minutes it was in your mouth?
Why do you think the taste of the cracker changed the longer it was in your mouth?
After 30 minutes, how did the appearance of the milk solution compare to that of the orange juice solution?

15. Enzymes in Action
Think and Discuss
Meat tenderizer contains an enzyme called papain. Based on your observations, what nutrient does papain act on?
Why do you think meat tenderizer makes cooked meat tender?

16. Stomach
From the esophagus, food passes through a valve and into the stomach, a muscular pouch located in the abdomen.
Mechanical digestion occurs as three layers of muscle produce a churning motion.
Chemical digestion occurs as cells lining the stomach release gastric juice.
Peristalsis moves the food, which is now a thick liquid called chyme (kym), into the small intestine.

17. Small Intestine
The small intestine is where most chemical digestion and absorption of nutrients takes place.
Liver The role of the liver is to produce bile. Bile is a substance that physically breaks up large fat droplets that clump together.
Gallbladder Bile flows from the liver into the gallbladder, the organ that stores bile.
Pancreas The pancreas secretes enzymes into the small intestine that complete the breakdown of carbohydrates, proteins, and fats.
The lining of the small intestine is covered with millions of tiny fingerlike projections called villi (singular, villus).

18. The Large Intestine
The large intestine is about 5 feet long and 3 inches wide.
As the material moves through the large intestine, most of the remaining water is absorbed into the blood.

19. Vocabulary
digestion
The process by which the digestive system breaks down food into molecules that the body can use.
enzyme
A chemical that speeds up reactions in the body.
absorption
The process by which nutrients pass through the lining of the digestive system.
pharynx
The upper portion of the throat; the junction between the digestive and respiratory systems.
epiglottis
A flap of tissue that seals off the trachea when food or liquid is swallowed.
peristalsis
Waves of muscle contractions that push food through the digestive system.

20. Vocabulary
chyme
A thick mixture of food and gastric juices formed in the stomach.
bile
A substance produced by the liver that aids in digestion by breaking up large fat droplets.
gallbladder
The organ that stores bile and releases it into the small intestine.
villi
Tiny fingerlike projections lining the small intestine, through which nutrients are absorbed into the blood.

21. QuickTake Quiz
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22. End of Section 10.1 Click on this slide to end this presentation.