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Brave Hearts
Pump it up
The heart represents love, emotion and the centre of our being – but essentially it is a simple pump.
As long as our hearts are beating, we are alive. We have known how and why it beats for hundreds of years, however diagnosing or treating defects or diseases that threaten to stop the heart is recent history.
The centre of our being | Your heart is almost in the centre of your chest between the lungs. It is tipped slightly, so that a part of it taps against the left side, which is what makes it feel as though it is located there.
In simplest terms, the heart is a pump. It is there to push the blood that delivers oxygen and nutrients around your entire body, and to carry depleted blood back again.
The heart needs an electrical spark to power the pump. A group of cells at the top of the right atrium set off an electrical impulse that generates a heartbeat.
The human heart beats around 100,000 times a day or 53 million times a year.
Every minute, the heart pumps five litres of blood around the adult body. This requires a very strong muscle. Your heart is almost all muscle. It is called the myocardium.
Think of your heart as two pumps sitting on either side of a shared wall or partition. This wall is called the septum.
These right and left sides are further divided into two halves. Each side has an upper receiving chamber, called an atrium, and a lower pumping chamber, called a ventricle.
The four chambers of the heart | When your right atrium has filled with oxygen-depleted blue blood from your body, it squeezes this gently down into your right ventricle. Your right ventricle then pumps this blood back through the pulmonary artery to your lungs, for a fresh oxygen supply and to eliminate carbon dioxide.
The oxygenated blood returns to the left atrium and is squeezed down into your left ventricle. Your left ventricle then pumps this life-giving blood out, via the aorta, into the extensive network of arteries and capillaries to every part of your body.
The left ventricle must be the strongest chamber to squeeze down so powerfully that it forces blood through the whole circulatory system. The right ventricle has only to propel blood through the nearby low-pressure lungs.
The blood vessels | The aorta is the main artery carrying oxygen and nutrient-rich blood away from the left ventricle into your systemic circulatory system. It is your largest blood vessel, and is almost the diameter of a garden hose.
The wall of an artery has a strong muscular middle layer that contracts and relaxes, to control the flow of blood through the increasingly smaller arteries and capillaries to the surrounding tissue, where the exchange of oxygen and carbon dioxide occurs. Capillaries are so small that it takes 10 of them to equal the thickness of a human hair.
The capillaries then transport the waste-rich and oxygen-poor blood to the veins and back to your heart. Veins are similar to arteries but not as strong or as thick. Unlike arteries, veins contain valves that ensure blood flows in only one direction, back to the heart, against the force of gravity.
A kitchen tap would need to be turned on all the way for at least 45 years to equal the amount of blood pumped around the body in a lifetime.