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Answer KeyDIGESTIVE SYSTEM

1. The liver stores glycogen, makes proteins, breaks down toxic substances, and secretes bile.

2. Bile breaks fat globules into small droplets, which exposes a greater surface area of the fats to the action of digestive enzymes.

3. The gallbladder stores and concentrates bile.4. a.Liver

b.Common bile ductc.Stomachd.Main pancreatic ducte.Pancreasf.Small intestineg.Gallbladder

5. In the passage, suspended means “dispersed in a liquid.” In the sentence, the term means “disbarment of a privilege.”

6. c

© Houghton Mifflin Harcourt Publishing CompanyHolt McDougal Biology 1 Digestive and Excretory Systems

Name________________________________Class____________________Date____________________ACTIVE READING WORKSHEETS

DIGESTIVE AND EXCRETORY SYSTEMS

Digestive System

Read the passage below, which covers topics from your textbook. Answer the questions that follow.

The liver is a large organ located to the right of the stomach. The liver performs numerous functions in the body, including storing glucose as glycogen, making proteins, and breaking down toxic substances, such as alcohol. The liver also secretes bile, which is vital in the digestion of fats. Bile breaks fat globules into small droplets, forming a milky fluid in which fats are suspended. This process exposes a greater surface area of fats to the action of digestive enzymes and prevents small fat droplets from rejoining into large globules.

The bile secreted by the liver passes through a Y-shaped duct. The bile travels down one branch of the Y and then up the other branch to the gallbladder, a saclike organ that stores and concentrates the bile. When chyme is present in the small intestine, the gallbladder releases bile through the common bile duct into the small intestine.

Write the answer to each question in the space provided.SKILL: Identifying Main Ideas1. What are three functions of the liver?

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2. If bile is not a digestive enzyme, how can it aid in the digestion of fats?________________________________________________________________________________________________________________________________________________________________________________________________

© Houghton Mifflin Harcourt Publishing CompanyHolt McDougal Biology 2 Digestive and Excretory Systems

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3. What is the function of the gallbladder?________________________________________________________________

Write your answers in the spaces provided.SKILL: Interpreting Graphics4. The diagram below illustrates parts of the digestive system. Complete the

diagram by adding the following labels: “Common bile duct,” “Main pancreatic duct,” “Gallbladder,” “Liver,” “Pancreas,” “Small intestine,” and “Stomach.”

Read the question and write your answer in the space provided.SKILL: Vocabulary Development5. Compare the meaning of the term suspended in the passage with its meaning

in the sentence “The intoxicated driver will have his license suspended.”_________________________________________________________________________________________________________________________________________________________________________________________________________

Circle the letter of the phrase that best completes the statement.6. The gallbladder releases bile into the small intestine when

a. fats are present in the stomach. c. chyme is present in the small intestine.b. glycogen is present in the liver. d. fats are present in the small intestine.

© Houghton Mifflin Harcourt Publishing CompanyHolt McDougal Biology 3 Digestive and Excretory Systems