About this quiz

Your body is the one thing you carry everywhere, but most of us know surprisingly little about how it works. This science quiz asks twenty questions about bones, organs, blood and the senses.

It starts with the basics and works up to the kind of facts that come up in pub quizzes. Each answer comes with a short explanation. This quiz is for fun and general knowledge, not medical advice.

Answers explained

Show the answers (spoilers)

  1. What is the largest organ of the human body?

    Skin. Your skin makes up roughly a sixth of your body weight.

  2. Which organ pumps blood around the body?

    Heart. An adult heart beats roughly 100,000 times a day.

  3. How many teeth does an adult usually have?

    32. That includes four wisdom teeth, which many people never get.

  4. What is the hardest substance in the human body?

    Tooth enamel. Enamel can’t grow back, because it contains no living cells.

  5. Which is the longest bone in the body?

    Femur. The femur, or thigh bone, is also the strongest bone in the body.

  6. Where is the smallest bone in the body?

    The ear. The stapes, in the middle ear, is only about 3 mm long.

  7. What do red blood cells carry around the body?

    Oxygen. A protein called haemoglobin carries the oxygen and gives blood its red colour.

  8. Roughly how much blood does an adult have?

    5 litres. That’s enough to fill about nine pints.

  9. Which organs filter the blood to make urine?

    Kidneys. Your kidneys filter about 180 litres of fluid from your blood every day.

  10. Which part of the eye controls how much light gets in?

    Iris. The iris widens or narrows the pupil, the black opening in its centre.

  11. Which organ can regrow after part of it is removed?

    Liver. The liver can grow back to full size even after more than half of it is removed.

  12. Which is the largest muscle in the body?

    Gluteus maximus. Your gluteus maximus, in your buttock, helps keep you upright when you stand and climb.

  13. Where does the body get most of its vitamin D?

    Sunlight on the skin. Skin makes vitamin D in sunlight, but UK winter sunlight isn’t strong enough to make much.

  14. Which blood type is known as the universal donor?

    O negative. AB positive is known as the universal recipient.

  15. Which organ makes insulin?

    Pancreas. Insulin lets your cells take in sugar from the blood to use for energy.

  16. Which part of the body has no blood supply and takes oxygen straight from the air?

    The cornea. The cornea is the clear front window of the eye.

  17. Roughly how long is the small intestine?

    About 6 metres. It’s called small because it’s narrower than the large intestine, not because it’s shorter.

  18. What are the tiny air sacs in your lungs called?

    Alveoli. You have hundreds of millions of them, where oxygen passes into your blood.

  19. Which part of the brain controls balance and coordination?

    Cerebellum. Cerebellum is Latin for “little brain”.

  20. Roughly how many times does a person blink in a day?

    About 15,000. Most people blink 15 to 20 times a minute, but less when staring at a screen.