The Human Body [The Digestive System]

• digestion

• absorption

• saliva

• enzyme

Vocabulary

• What functions are carried out in the digestive system?

• What roles do the mouth, esophagus, and stomach play in digestion?

Key Concepts

The Digestive Process Begins

• epiglottis

• esophagus

• mucus

• peristalsis

• stomach

Discover Activity

How Can You Speed Up Digestion?

1. Obtain two clear jars with lids. Fill the jars with equal amounts of water.

2. Place a whole sugar cube into one jar and a crushed sugar cube into the other jar.

3. Fasten the lids on the jars. Holding one jar in each hand, shake the two jars gently for equal amounts of time.

4. Place the jars on a flat surface and observe whether the whole cube or crushed cube dissolves faster.

Multiple Choice

Which would take longer to digest?

• A large piece of food

• Food that has been cut up into many small pieces

In 1822, a man named Alexis St. Martin was wounded in the stomach. Dr William Beaumont saved St. Martin's life. The wound, however, left an opening in St. Martin's stomach that never healed completely. Beaumont realized that by looking through the opening in St. Martin's abdomen, he could observe what was happening inside the stomach.

Beaumont observed that food changed chemically inside the stomach. He hypothesized that chemical reactions in the stomach broke down foods into smaller particles. Beaumont removed liquid from St. Martin's stomach and analyzed it. The stomach liquid contained an acid that played a role in the breakdown of foods into simpler substances.

Functions of the Digestive System

Beaumont's observations helped scientists understand the role of the stomach in the digestive system. The digestive system has three main functions. First, it breaks down food into molecules the body can use. Then, the molecules are absorbed into the blood and carried throughout the body. Finally, wastes are eliminated from the body.

As food moves through the digestive system, digestion, absorption, and elimination occur one after the other in an efficient, continuous process.

Which organs does food pass through after leaving the mouth?

The Digestive System

The picture shows the organs of the digestive system, which is 9 meters long from beginning to end.

This means it is close to 30 feet long!

Chemicals produced by the body break food into their smaller chemical building blocks. For example, the starch in bread is broken down into individual sugar molecules.

Chemical Digestion

Foods are physically broken down into smaller pieces. Mechanical digestion occurs when you bite into a sandwich and chew it into small pieces.

Mechanical Digestion

Digestion
The process by which your body breaks down foods into small nutrient molecules.

Multiple Choice

What is digestion?

• The process by which your body breaks down foods into small nutrient molecules

• The process by which nutrient molecules pass through the wall of your digestive system and into your blood

Multiple Choice

What kind of digestion occurs when you bite into a sandwich?

• Mechanical Digestion

• Chemical Digestion

Multiple Choice

What kind of digestion occurs when the starch in bread is broken down into individual sugar molecules?

• Mechanical Digestion

• Chemical Digestion

Absorption and Elimination

After your food is digested, the molecules are ready to be transported throughout your body. Absorption is the process by which nutrient molecules pass through the wall of your digestive system into your blood. Materials that are not absorbed, such as fiber, are eliminated from the body as wastes.

Multiple Choice

What is absorption?

• The process by which your body breaks down foods into small nutrient molecules

• The process by which nutrient molecules pass through the wall of your digestive system and into your blood

Multiple Choice

What is the process by which your body gets rid of materials that are not absorbed?

• Absorption

• Elimination

• Mechanical Digestion

• Chemical Digestion

Click the Link

The Digestive System

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