The heart: what it is, how it works, when it fails

Abstract

For centuries, the human heart seemed beyond human understanding. Every aspect of the human heart elicits fascination. Thus, every age, every culture, every civilization and every religion has developed theories and beliefs about it, which overlap, support, and sometimes undermine one another.

The heart is celebrated as the home of faith, love and courage, the seat of the soul. No other organ has inspired so many poets, writers, painters, and religious thinkers, and references to it abound in advertising, cultural kitsch, song lyrics, and everyday language and imagery.

The heart is a hollow muscular organ slightly bigger than a clenched fist. The adult human heart weighs between 200 and 425 grams. It is located between the lungs in the middle of the chest, behind and slightly to the left of the breastbone.

From the moment it begins beating until the moment it stops, the human heart works tirelessly. It beats 60-72 times per minute in an adult at rest but can accelerate to 160-180 beats per minute during exercise, anxiety or fear. In a day the heart beats 100,000 times.

In an average lifetime, the heart beats more than three billion (3,000,000,000) times without ever pausing to rest.

Work performed by this amazing muscular pump is equivalent to a human being lifting 6kg of weight to a height of 1.5 m every minute.

The heart propels 5 liters of blood through the circulation every minute. If all the blood vessels in the body could be lined up, the distance covered will be about 90,000km, which is more than twice the distance round the world at the equator.

The heart pumps 7000litres of blood through this labyrinth every day. At that rate it could fill a 10km long goods train with blood in 60 years. It generates enough power to drive a lorry round the world in 4 years.