We all know how the heart works, pumping blood around our body to all our organs. But this wasn't always common knowledge, it's thanks to 16th-century scientist, William Harvey that we discovered the real purpose of the heart. Helen Cowan tells of the discovery of the heartbeat.

What we now know about the heart

Medical illustration of heart

When you feel your pulse at your wrist, it’s reflecting the pumping action of your heart. Blood moves around the body in two circuits: one from the heart to the lungs and back again (the pulmonary circulation); and one from the heart, through the aorta, to every organ in the body and back again (the systemic circulation).

We take for granted that the heart drives the circulation, moving blood in continuous circuits—not being consumed by the body organs but recycled. It is very well known today. Yet, without a little known scientist named William Harvey, we might still believe some very strange ideas about our inner workings.

 

What we used to think about the heart

Love heart

The ancient Egyptians recognised the importance of the heart as a source of emotions and personality (and so today, we still speak of being ‘heartbroken’, ‘disheartened’ and ‘hard-hearted’). During mummification, other organs were removed and the brain thrown away (as its only function was thought to be to pass mucus to the nose). The heart however, was left in the body with significance in the afterlife.

No value was given to the heart in the circulation of blood. Instead the liver was believed to be at the centre of the circulatory system—just like when the Earth was considered to be the centre of the solar system. Blood was thought to be made in the liver, ebbing and flowing in sea-like waves from the liver to all the body organs where it was devoured.

Once in the heart, the blood was thought to ‘boil’ changing in colour from blue blood to red blood. We now know, of course, that the change in blood colour is due to the blood actually leaving the right side of the heart, picking up oxygen from the lungs and returning to the left side of the heart.

 

How Harvey transformed our thinking

William Harvey illustration of circulatory system in the arm

Speaking in Latin and accompanied by lutes, Harvey would perform dissections in front of packed lecture theatres. Operating on more than eighty species of mammal, he would cut or clamp the main artery and vein attached to the heart, subsequently showering the audience with blood as the heart beat or completely emptying the heart and ceasing the circulation. A rather graphic way to demonstrate that the heart did beat and thus drive the circulation around the body.

Transparent cold blooded fish (whose hearts beat more slowly than humans) would be held up for observation, to show the heart in action, while one unfortunate man with a chest injury that exposed his heart offered a rare insight.

Harvey’s discovery in 1628 demolished theories that had stood for more than a thousand years. His hard work and courage to challenge opinion paid off. Oh, and the fact that he was the physician to King James I and King Charles I probably helped him too—sometimes it’s what you know as well as who you know that matters.

Helen Cowan completed a PhD in cardiac pharmacology at Oxford in 2002. She is a qualified nurse and has written for the British Journal of Cardiac Nursing, and worked as a columnist in the Nursing TimesRead more from Helen here.

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