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Organs at work

Organs at work: a chapter of The Human Body Book, with the facts about your own body that are worth knowing.

10 cards · Science

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Each Zap teaches up to 5 new cards, so you learn the deck a few at a time.

Checked by the Brain Zap team · reviewed 26 Oct 2026

Sources: Human body (Encyclopaedia Britannica), Health A to Z (NHS)

Preview

  • The body's largest organ

    Show answer: The body's largest organ

    Skin

    Learn more: An adult's skin weighs about 4 kg and covers nearly 2 square metres, keeping germs out and water in.

  • The largest organ inside the body

    Show answer: The largest organ inside the body

    Liver

    Learn more: It filters the blood, stores energy and makes bile, and it can regrow after part is removed.

  • Two organs that filter blood and make urine

    Show answer: Two organs that filter blood and make urine

    Kidneys

    Learn more: Together they filter about 180 litres of fluid a day and return almost all of it to the blood.

  • Where most of your food is absorbed

    Show answer: Where most of your food is absorbed

    Small intestine

    Learn more: Millions of tiny finger-like villi give it a huge surface for passing food into the blood.

  • The acid in your stomach that kills germs

    Show answer: The acid in your stomach that kills germs

    Hydrochloric acid

    Learn more: The stomach lining makes fresh mucus all the time, so the acid doesn't digest the stomach itself.

About this topic

Your organs work as a team: the stomach and intestines take food apart, the liver and kidneys clean the blood, and glands such as the pancreas and thyroid send out the hormones that keep everything in balance. Most of this happens without a single thought from you. Some organs, such as the appendix, gallbladder and spleen, can even be removed, and the rest of the team takes over their work.

This is a chapter of The Human Body Book. Each card asks one question, with a hint before you answer and a short reason after. Once you know most of this chapter, the next one starts arriving in your Daily Zap.

All 10 cards

  1. The body's largest organ

    Skin

    Learn more: An adult's skin weighs about 4 kg and covers nearly 2 square metres, keeping germs out and water in.

  2. The largest organ inside the body

    Liver

    Learn more: It filters the blood, stores energy and makes bile, and it can regrow after part is removed.

  3. Two organs that filter blood and make urine

    Kidneys

    Learn more: Together they filter about 180 litres of fluid a day and return almost all of it to the blood.

  4. Where most of your food is absorbed

    Small intestine

    Learn more: Millions of tiny finger-like villi give it a huge surface for passing food into the blood.

  5. The acid in your stomach that kills germs

    Hydrochloric acid

    Learn more: The stomach lining makes fresh mucus all the time, so the acid doesn't digest the stomach itself.

  6. Organ that makes insulin

    Pancreas

    Learn more: Insulin lets cells take in sugar from the blood; without enough of it, a person has diabetes.

  7. Small pouch off the large intestine

    Appendix

    Learn more: It may store helpful gut bacteria; when it gets inflamed, appendicitis needs fast surgery.

  8. Stores the bile made by the liver

    Gallbladder

    Learn more: Bile breaks fat into tiny drops so it can be digested; people live fine without this organ.

  9. Organ that recycles old red blood cells

    Spleen

    Learn more: It also stores infection-fighting white cells; you can live without it, but catch some infections more easily.

  10. Gland in the neck that sets your metabolism

    Thyroid

    Learn more: Its hormones set how fast cells burn energy; it needs iodine, which is why salt often has some added.

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