Human Body Systems Quiz

Grade 3 · Science · Quiz

Test your knowledge of the major systems that keep the human body working.

Questions

1. Which organ is part of the respiratory system?

   1. Heart
   2. Stomach
   3. Lungs
   4. Brain
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   Answer: Lungs

   The lungs are the key organs of the respiratory system. They exchange oxygen and carbon dioxide with the blood through millions of tiny alveoli.

2. Bones are part of the skeletal system.

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   Answer: True

   The skeletal system includes all 206 bones, cartilage, and ligaments. Bones support the body, protect organs, and anchor muscles.

3. The stomach is part of the ___ system.

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   Answer: digestive

   The digestive system processes food from mouth to stomach to intestines. The stomach uses acids and enzymes to break food into smaller molecules.

4. What does the digestive system do?

   1. Pumps blood around the body
   2. Breaks food into nutrients
   3. Controls body movement
   4. Breathes in oxygen
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   Answer: Breaks food into nutrients

   The digestive system's job is to break large food molecules into small nutrients like glucose, amino acids, and fatty acids that cells can use.

5. Muscles can only pull, not push.

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   Answer: True

   Muscles work in pairs — one contracts (pulls) while the other relaxes. Your bicep pulls your forearm up; your tricep pulls it back down. Muscles cannot actively push.

6. Which gas do lungs remove from the blood and breathe out?

   1. Oxygen
   2. Nitrogen
   3. Carbon dioxide
   4. Water vapor
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   Answer: Carbon dioxide

   Carbon dioxide is a waste gas produced by cells when they use oxygen for energy. Blood carries CO2 to the lungs, where it's breathed out.

7. The brain, spinal cord, and nerves make up the ___ system.

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   Answer: nervous

   The nervous system is the body's communication network. The brain processes information; nerves carry signals at up to 200 miles per hour throughout the body.

8. Blood is part of the circulatory system.

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   Answer: True

   Blood is a living tissue that carries oxygen, nutrients, hormones, and waste products. About 55% of blood is plasma (liquid) and 45% is blood cells.

9. How many bones does an adult human body have?

   1. 100
   2. 150
   3. 206
   4. 350
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   Answer: 206

   Adults have 206 bones. Many of the separate bones babies are born with fuse together during childhood and adolescence.

10. The heart is a muscle.

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    Answer: True

    The heart is made of cardiac muscle — a special type that contracts rhythmically without stopping from birth to death. It beats about 2.5 billion times in a lifetime.

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