Blood flows to and from the heart through a series of actions. Here is a simple way of looking at what happens:
- When blood returns to the heart from throughout the body, it flows into the right atrium. That blood is now low on oxygen because it has been supplying oxygen throughout your body.
- The right atrium of your heart fills with this blood, which then flows into your heart's right ventricle. Next, the blood goes from your right ventricle to the lungs for an oxygen refill.
- To maximize the amount of blood in the right ventricle, the right atrium contracts - pushing the blood down into the ventricle.
- When the right ventricle is full, it contracts and blood is forced into the lungs.
- Once the blood has picked up oxygen, it moves from the lungs to the left atrium and then down into the left ventricle. The atrium then contracts and then the ventricle contracts, like it did on the right side.
- The right and left atriums contract at the same time. The right atrium pushes the oxygen-low blood into the right ventricle. The left atrium pushes the oxygenated blood from the previous cycle into the left ventricle.
- The left ventricle contracts, sending the blood throughout the body.
- Eventually, the process begins all over again.