Body Systems and Senses — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Digestion begins in the mouth where teeth chew food and saliva starts breaking it down.
Chewing breaks food into smaller pieces while saliva adds enzymes that begin breaking down starches.
2. Food travels from the mouth down a long tube called the esophagus to reach the stomach.
The esophagus uses wave-like muscle contractions called peristalsis to move food from the throat to the stomach.
3. The stomach mixes food with strong acids and enzymes to break it into a thick liquid.
The stomach churns food and uses acid and enzymes to break proteins down into smaller pieces.
4. Most nutrients are absorbed in the small intestine through tiny finger-like structures called villi.
The small intestine has millions of villi that increase surface area so nutrients can pass into the bloodstream.
5. The large intestine absorbs water from leftover food before waste leaves the body.
The large intestine pulls water back into the body and packages the remaining waste for removal.
6. The correct order after the stomach is small intestine, then large intestine.
After the small intestine finishes absorbing nutrients, the large intestine handles water absorption and waste storage.
7. Saliva in the mouth contains enzymes that help break down starches in food.
Salivary enzymes start breaking starches into sugars even before food leaves the mouth.
8. Strong acid in the stomach helps kill harmful bacteria that may be in food.
Stomach acid not only breaks down proteins but also destroys many germs that arrive with food.
9. Waste finally leaves the body after passing through the large intestine.
After the large intestine forms solid waste, it exits the body through the rectum and anus.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Mouth
→ Chews food and adds saliva
Tube that pushes food to the stomach
Esophagus
→ Tube that pushes food to the stomach
Chews food and adds saliva
Stomach
→ Mixes food with acid and enzymes
Absorbs nutrients into the blood
Small intestine
→ Absorbs nutrients into the blood
Mixes food with acid and enzymes
Each digestive organ has a specific job, and food moves through them in order: mouth, esophagus, stomach, then small intestine.