The Normal Heart

‘The primary function of the heart is to pump blood. It pumps blood twenty four hours a day seven days a week and is located between your lungs in the middle of your chest.. Sometimes it has to pump a lot of blood (when you are exercising/running) and then sometimes it has to pump less blood (when you are relaxing / sleeping).

The heart has four chambers, though there are many children born whose hearts don't have all these chambers. The upper chambers are called the left and right atria and the lower chambers are called the left and right ventricles. A valve links the top and bottom chambers on each side, the mitral valve on the left side and the tricuspid valve on the right side. A muscle called the septum (central heart wall) separates the left and right atria and the left and right ventricle' (http://www.heartsplay.ie/)

Blood returning from the body enters the right atrium by way of the superior and inferior vena cava, from where it passes to the right ventricle via the tricuspid valve. When the heart muscle contracts, the tricuspid valve closes, and the pressure in the right ventricle rises and forces open the pulmonary valve allowing blood to enter the lungs via the pulmonary artery.

The main arteries of the lungs branch into very many smaller vessels (much like the structure of a tree: trunk, branches, twigs), with much thinner walls which are able to take oxygen from the air in the airways of the lungs into the blood stream. The oxygenated blood then returns from the lungs in the four pulmonary veins and enters the left atrium.

From the left atrium the oxygenated blood is passed via the mitral valve to the left ventricle. Again, when the heart muscle contracts, the mitral valve closes, and the pressure in the ventricle rises forcing open the aortic valve which allows blood to flow into the aorta, and from there in to the many vessels which supply the body with blood.

Therefore the right side of the heart pumps blood to the lungs, which is a relatively easy task, whilst the left side has the more difficult task of pumping blood all around the body. As a result, the pressures in the left ventricle are generally about four times greater than that in the right ventricle, and the wall of the left ventricle is thicker than that of the right.

More detailed information about all combination of heart defects can be found at the Royal Hospital of Melbourne website click here.