The digestive system online exercise for high school - Free Printable

Here is the completed worksheet with the correct answers filled in, along with explanations for each answer based on the human digestive system:

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1. Digestion is a process in which complex food material is broken down into simpler _________.
✔ Answer: *substances*
🔹 Explanation: Digestion breaks down large, complex molecules like carbohydrates, proteins, and fats into smaller, simpler substances (e.g., glucose, amino acids, fatty acids) that the body can absorb.

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2. The digestion of food in humans takes place in the alimentary canal, which is a long tube extending from ______ to the ______.
✔ Answer: *mouth* to the *anus*
🔹 Explanation: The alimentary canal starts at the mouth where food enters and ends at the anus, where undigested waste is expelled.

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3. The food is taken in through the mouth. It is chewed and mixed with the _________ in buccal cavity.
✔ Answer: *saliva*
🔹 Explanation: In the mouth (buccal cavity), food is mechanically broken down by teeth and mixed with saliva, which contains enzymes like amylase that begin chemical digestion.

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4. Saliva is a digestive juice secreted by the ________________.
✔ Answer: *salivary glands*
🔹 Explanation: Saliva is produced by three pairs of salivary glands: parotid, submandibular, and sublingual glands.

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5. The chewed food enters into the food pipe or ___________ and is then slowly pushed into a bag-like structure called ___________.
✔ Answer: *oesophagus* and *stomach*
🔹 Explanation: After chewing, food is swallowed and travels down the oesophagus via peristalsis (muscular contractions) into the stomach, a muscular sac where further digestion occurs.

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6. The hydrochloric acid in the stomach kills the __________ in the food and makes food __________.
✔ Answer: *germs* (or bacteria) and *acidic*
🔹 Explanation: Hydrochloric acid (HCl) in gastric juice destroys harmful microorganisms in food and creates an acidic environment suitable for pepsin enzyme activity.

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7. The food then goes into a highly coiled tube called small intestine. The small intestine receives secretions from the ________________.
✔ Answer: *liver and pancreas*
🔹 Explanation: The small intestine receives bile from the liver (stored in gallbladder) and pancreatic juices from the pancreas. These help in digesting fats, proteins, and carbohydrates.

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8. The inner surface of the small intestine has finger-like projections called ________. The villi have extensive network of blood _________.
✔ Answer: *villi* and *capillaries*
🔹 Explanation: Villi increase the surface area for absorption. Each villus contains a network of capillaries and a lacteal (lymphatic vessel) to absorb nutrients into the bloodstream and lymphatic system.

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9. The __________ food is passed into the large intestine. It is wider than the small intestine.
✔ Answer: *undigested*
🔹 Explanation: After most nutrients are absorbed in the small intestine, the remaining undigested food passes into the large intestine (colon).

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10. Excess of water and salts are absorbed here and undigested waste is passed out of the body through the _________.
✔ Answer: *rectum and anus*
🔹 Explanation: The large intestine absorbs water and electrolytes, forming solid feces. Feces are stored in the rectum and expelled through the anus during defecation.

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✔ Final Completed Worksheet:

1. substances
2. mouth, anus
3. saliva
4. salivary glands
5. oesophagus, stomach
6. germs, acidic
7. liver and pancreas
8. villi, capillaries
9. undigested
10. rectum and anus

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