





The heart’s four chambers are:


The heart’s two atria are both located on the top of the heart. They are responsible for receiving blood from your veins.

The heart’s two ventricles are located in the bottom of the heart. They are responsible for pumping blood into your arteries.

Your atria and ventricles contract to make your heart beat and to pump the blood through each chamber. Your heart chambers fill up with blood before each beat, and the contraction pushes the blood out into the next chamber. The contractions are triggered by electrical pulses that start from the sinus node, also called the sinoatrial node (SA node), located in the tissue of your right atrium.

The pulses then travel through your heart to the atrioventricular node, also called the AV node, located near the center of the heart between the atria and the ventricles. These electrical impulses keep your blood flowing in proper rhythm.

The heart has four valves, one each at the downstream end of each chamber, so that, under normal conditions, blood can’t flow backward, and the chambers can fill with blood and pump blood forward properly. These valves can sometimes be repaired or replaced if they become damaged.

The heart’s valves are:

  • Tricuspid (right AV) valve. This valve opens to allow blood to flow from the right atrium to the right ventricle.
  • Pulmonary valve. This valve opens to allow blood to flow from the left ventricle into the pulmonary artery to the lungs, so that the heart and rest of the body can receive more oxygen.
  • Mitral (left AV) valve. This valve opens to let blood flow from the left atrium to the left ventricle.
  • Aortic valve. This valve opens to let blood leave the left ventricle so that the blood can flow to the heart and the rest of body, save the lungs.





The structure of the heart’s blood supply is called the coronary circulatory system. The word “coronary” comes from the Latin word meaning “of a crown.” The arteries that fuel the heart’s muscle encircle the heart like a crown.

Coronary heart disease, also called coronary artery disease, typically develops when calcium containing cholesterol and fat plaques collect in and hurt the arteries that feed the heart muscle. If a portion of one of these plaques ruptures, it can suddenly block one of the vessels and cause the heart muscle to begin to die (myocardial infarction) because it’s starved for oxygen and nutrients. This can also occur if a blood clot forms in one of the arteries of the heart, which can happen right after a plaque rupture.