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A hearty activity

By Mike, 14 February 2013 Activity

Lay the heart on a chopping board.

Lay the heart on a chopping board.

It’s Valentine’s Day! What better way to celebrate than with a heart dissection?

sharp hazard iconrotten food hazard iconSafety: This experiment requires cutting with a sharp knife. Ask an adult to help. Make sure you wash your hands thoroughly after the dissection.

You will need

  • A heart (ox or cow hearts are a good size, but a sheep’s heart will also work. Ask your local friendly butcher to get one for you)
  • Chopping board
  • Sharp knife
  • Soap and water

What to do

  1. Examine the outside of the heart, and find the large ‘tubes’ or holes which lead into it. That is the top of the heart. How many tubes can you see?
    Notice the 'tubes leading in ad out at the top.

    Notice the ‘tubes’
    leading in and out at the top.

  2. Look at the large white patches of fat surrounding them. Find the diagonal line which leads away from the fat down towards the pointy part (or ‘apex’) of the heart.
  3. If you are right handed, lay the heart on the chopping board with the top towards your left hand, and the diagonal line facing up. If you are left handed, face the top towards your right.
  4. Take your sharp knife and slice through the middle of the heart – hold your knife horizontal to the chopping board and pointing away from you as you cut. Very carefully move its blade back and forth along the length of the heart until you have two complete halves.
  5. Look inside the heart. Can you see the two large cavities? Can you see stringy bits near the top of the cavities?
  6. Remember to throw out the heart when you’re finished, and wash your hands carefully afterwards!

What’s happening?

Cut horizontally through the heart.

Cut horizontally through the heart.

Blood is necessary for oxygen and nutrients to get to your body’s cells, and for waste products to be removed. To make its way around, muscles surrounding some parts of your circulatory system pulse in a steady beat, squeezing the blood through. The heart is the largest of these pulsing muscles.

What you think of as a single heart is actually made of two parts – a left pump and a right pump. That’s right, in some ways you have two hearts! That’s why there are four tubes at the top of the heart. Each half has a tube going into it (tubes leading to the heart are called veins), and a tube going away from it (tubes leading away are called arteries).

Notice the 'heart strings' near the valve.

Notice the ‘heart strings’ near the valve.

Notice that none of the veins are really blue. Veins look that colour only when seen through your skin, for the same reason that the sky looks blue (caused by ‘Rayleigh scattering’ of light).

Why are there two pumps? Basically, your heart needs to do a lot of work. To get oxygen and release carbon dioxide, blood needs to go to the lungs and be pushed through a large network of tiny vessels called capillaries. The smaller of the two pumps (your right half) therefore pumps blood to your lungs. The bigger of the two pumps (your left half) receives the oxygenated blood from the lungs and pushes it around the rest of your body.

To make sure blood only goes one way, there are neat little doors which only move one way. These are ‘valves’. Those strings you see inside the heart make sure the valves only open in one direction.


Your heart is an incredibly important organ. Even so, many things can go wrong with it.

The heart is made of two halves.

The heart is made of two halves.

Although the heart has litres of blood pumping through it every hour, it still needs its own personal supply. If any of the heart’s own arteries are clogged, such as from a build up of plaque due to too much LDLs (a bad form of cholesterol), the heart won’t get oxygen and will stop working. This is what causes heart attacks.

It’s important to ensure your heart is healthy. Just like any muscle in your body, your heart can be made stronger through working it harder, which is why exercise is good for you. Half an hour every day of making your heart beat faster – even if it’s just a walk – could make all the difference. With a healthy diet which reduces the amount of bad cholesterol, and avoiding smoking, you can be sure that your heart will return the favour well into old age.

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