What Makes the Sound of Our Heartbeat?

by Atalanta Nelson-Smith 

When you hear your own, or someone else’s heartbeat, it’s not the heart contracting/beating which makes the noise, it’s actually the valves within your heart closing. 

Blood journeys around the body through your arteries, veins and capillaries where it exchanges substances such as oxygen and carbon dioxide with the tissue and cells within the body. It then returns to the heart, full of carbon dioxide, so it can be pumped through the lungs to lose carbon dioxide and gain oxygen. It then travels from the lungs to the heart where it is pumped to the brain and body to repeat its journey around the body. When it enters the heart, from the body it goes through the vena cava on the right or and when oxygenated blood enters the heart from the lungs, it goes through the pulmonary vein on the left. 

From the vena cava or pulmonary vein, it flows into the atria (the top chambers of the heart), which increase in pressure and the atria contracts so it forces open the atrioventricular valve, the first valve. The blood rushes into the ventricles (the lower chambers of the heart) and once pressure behind the valve (from the atria) has decreased enough, and the pressure in front of the valve (from the ventricles) has increased enough, the atrioventricular valves shut. This makes the sound of the first heart beat.

Then, the ventricles will then contract and force blood up through the semilunar valves, which go to the pulmonary artery on the right or the aorta on the left. The pressure once again increases in front of the valve (in the pulmonary artery or aorta) and decreases behind it (in the ventricles), causing the semilunar valves to shut, making the second heart beat.