Heart

The heart is a muscular organ about the size of a fist, located just behind and slightly left of the breastbone. The heart pumps blood through the network of arteries and veins called the cardiovascular system.
The heart has four chambers:
1. The right atrium receives blood from the veins and pumps it to the right ventricle.
2. The right ventricle receives blood from the right atrium and pumps it to the lungs, where it is loaded with oxygen.
3. The left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle.
4. The left ventricle (the strongest chamber) pumps oxygen-rich blood to the rest of the body. The left ventricle’s vigorous contractions create our blood pressure.

heart attack

A heart attack occurs if the flow of oxygen-rich blood to a section of heart muscle suddenly becomes blocked. If blood flow isn't restored quickly, the section of heart muscle begins to die. The good news is that excellent treatments are available for heart attacks. These treatments can save lives and prevent disabilities. Heart attack treatment works best when it's given right after symptoms occur.