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Back Lesson Print Name Class Date Skills Worksheet Directed Reading A Section: The Digestive System ______ 1. What is the digestive system? a. the liver, pancreas, and small intestine b. a group of organs that work together to break down food c. the large intestine, gallbladder, and esophagus d. a group of veins and arteries that work together to digest food DIGESTIVE SYSTEM AT A GLANCE ______ 2. Which of the following organs is NOT part of the digestive tract? a. stomach b. pharynx c. large intestine d. kidneys 3. Food passes through some of the organs of the digestive system but not others. Which organs does food NOT pass through? BREAKING DOWN FOOD ______ 4. What are the two main kinds of digestion? a. mechanical and chemical b. mechanical and liquid c. mechanical and solid d. mechanical and heat 5. The kind of digestion that takes place when you chew your food is . 6. When your body breaks down food into nutrients, digestion takes place. 7. The major types of nutrients are , fats, and proteins. 8. What substances cut up the protein chains? 9. Proteins are made up of chains of smaller molecules called . Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 1 The Digestive and Urinary Systems Back Lesson Print Name Class Date Directed Reading A continued DIGESTION BEGINS IN THE MOUTH 10. Why is chewing important? For each kind of tooth listed, write whether it shreds, grinds, or mashes food. 11. premolars 12. incisors 13. canines 14. molars 15. As you chew your food, it is mixed with . 16. Saliva changes complex carbohydrates into , which are easier to digest. 17. How does the food get from your mouth to your throat? 18. What is the function of the esophagus? THE HARSH ENVIRONMENT OF THE STOMACH 19. What does the stomach do? 20. What do glands in the stomach produce? 21. What happens to most of the bacteria that you swallow with your food? 22. When the food moves out of the stomach, it is a soupy mixture called . Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 2 The Digestive and Urinary Systems Back Lesson Print Name Class Date Directed Reading A continued 23. Where does the chyme go when it leaves the stomach? THE PANCREAS AND SMALL INTESTINE 24. What organ makes fluid that protects the small intestine from the acid in the chyme? 25. The pancreas produces to regulate blood sugar. 26. Why is the small intestine called “small”? 27. What do the villi in the small intestine do? THE LIVER AND GALLBLADDER ______28. Which of the following is NOT a job of the liver? a. It stores bile. b. It stores nutrients. c. It breaks down toxins. d. It breaks up fat. 29. What is the job of the gallbladder? 30. What does bile do? 31. Which organ breaks down chemicals in the body such as alcohol and drugs? Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 3 The Digestive and Urinary Systems Back Lesson Print Name Class Date Directed Reading A continued THE END OF THE LINE ______32. Which of the following is NOT a job of the large intestine? a. absorbing water b. producing fiber c. producing feces d. storing excess material 33. What is fiber? 34. How does solid waste, or feces, leave the body? Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 4 The Digestive and Urinary Systems Back Lesson Print PAGE TEACHER RESOURCE Answer Key Directed Reading A 34. It is stored in the rectum until it is expelled through the anus. SECTION: THE DIGESTIVE SYSTEM 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. SECTION: THE URINARY SYSTEM B D pancreas, liver, gallbladder A mechanical chemical carbohydrate enzymes amino acids When you chew your food, you break it into small, slippery pieces. These pieces are easier to swallow. They are also easier to digest. mashing shredding shredding grinding saliva simple sugars The tongue pushes it in. It squeezes food into the stomach. The stomach squeezes food with muscular contractions. This is mechanical digestion. The stomach also mixes the food with digestive juices. This is chemical digestion. acid and enzymes It is killed by stomach acid. chyme the small intestine pancreas hormones It is small in diameter. absorb nutrients A It stores bile. Bile breaks large fat droplets into small droplets so they can be digested more easily. liver B It is another name for a carbohydrate called cellulose, which is found in fruits and vegetables. Humans cannot digest fiber. 1. C 2. It removes waste products from the 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. blood. carbon dioxide and ammonia B A They clean, or filter, the blood. a harmful substance containing nitrogen B to keep water levels in balance, otherwise your body would swell up When you’re thirsty, ADH keeps your body from losing more water through urine. It signals the kidneys to take water from the nephrons and return it to the bloodstream. It causes the kidneys to make more urine. This decreases the amount of water in your blood. B through the urethra damage to nephrons can prevent normal kidney functioning and can lead to kidney disease Directed Reading B SECTION: THE DIGESTIVE SYSTEM 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. B C D A mechanical chemical amino acids enzymes C A C B saliva tongue esophagus stomach enzymes Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Science and Technology 75 The Digestive and Urinary Systems