Your heart pumps blood to all parts of your body, providing it with the oxygen and nourishment it needs to function. This pump is a muscle about the size of your clenched fist and lies in your chest cavity behind and slightly to the left of your breastbone. It has a right and left side separated by a wall and each side has a small collecting chamber, called an atrium, which leads into a large pumping chamber, or ventricle. Blood vessels lead in and out and to make sure that blood flows in the correct direction, valves guard the entrance and exit to these chambers.
The right side of your heart collects deoxygenated blood returning from the rest of your body and pumps it to your lungs to receive more oxygen. This blood returns directly to the left side of your heart, which pumps it out again to all parts of your body.
The atriums and ventricles work together by alternately contracting (squeezing) and relaxing. The contraction, known as systole, is when your heart contracts and pumps blood and diastole is when your heart relaxes so the chambers can refill with blood. The heartbeat is triggered by electrical impulses that travel down a special pathway through your heart.
At rest, an adult’s heart beats 60 to 100 times a minute (a child’s heart rate is higher).
Every heartbeat results in blood moving forward through your arteries. This is the pulse you can feel if you place two fingers over the artery at your wrist.
Your heart needs oxygen to function, but the blood being pumped through your heart doesn’t supply oxygen to the heart muscle itself. There are special blood vessels attached to the outside of the heart, called coronary arteries, which supply it with oxygen and nutrients.
TOMMORROW: What can go wrong?
This article originally appeared in Heart magazine, for the Heart and Stroke Foundation SA