The heart is a fist-sized organ located in the center of your chest behind your breastbone which pumps blood to all parts of the body. The heart is divided into four hollow sections called chambers. The top two chambers are called atria. The bottom two chambers are called ventricles. When the muscles in the heart contract or tighten, the blood in the bottom chambers is pushed out into the blood vessels. This pumping action propels your blood through your arteries out into your body. As the muscles of the heart relax, valves between the top and bottom chambers open so blood in the top chambers can flow into the bottom.
The heart is also divided into right and left halves. Blood leaving the right half of the heart goes to the lungs where it drops off carbon dioxide that is a waste product from the cells and picks up a fresh supply of oxygen. This blood immediately returns to the heart where it flows into the left side and is propelled out into the body to supply the cells with oxygen.
Why people need heart transplants
The heart is a complicated mechanism that must all work in sync in order to keep your blood flowing. Electric signals in the nerves trigger the muscles of the heart to contract and relax at the correct times. If these signals are interrupted, the rhythm of the heart can be disrupted which can affect how much blood is pushed out during each heart beat, or how hard the blood is pushed.
Like all the tissues in the body, the heart muscles need a constant supply of oxygen to stay healthy. If the blood vessels that carry blood to the muscles of the heart become clogged, part of the tissue of the heart can be damaged or even die. If this happens, the remaining muscle of the heart has to work even harder to push blood out to the body. Because the heart tissue is muscle, when the heart has to work harder, the muscle starts to bulk up and the heart becomes enlarged. This can make it even harder for the heart to contract to push blood out of the lower chambers.
Some people are born with damaged hearts that do not work correctly.