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Your heart is a pretty spectacular organ — a four - chambered, hollow muscle right smack in the middle of your chest. The heart’s job is to pump the blood that carries life - giving oxygen and other nutrients to every body tissue. To show how this works, the clever For Patients artists have drawn a cross section of your heart in Figure 1 - 1 tracing the path of blood flowing in and out and in and out and in … you get the idea

Right ventricle

As you can see, blood that has deposited oxygen and other nutrients throughout your body comes back to your heart. Here’s the rundown on what happens when it gets there:

1. The blood enters your heart at the superior vena cava, a large vein that opens into the right atrium, the first chamber of your heart

2. From the right atrium, blood spills down through a one - way “trapdoor” called the tricuspid valve and into the right ventricle.

3. When the right ventricle contracts (squeezes together), the blood is sent out of your heart through the pulmonary artery and into your lungs where it picks up a plentiful supply of oxygen.

4. The newly oxygenated blood flows back into your heart through the pulmonary vein into the left atrium. Then the blood spills down through a second one - way trapdoor called the mitral valve and into the left ventricle.

5. When the left ventricle contracts, blood is pushed up through the large artery called the aorta and out into your body.

In real life, as opposed to a drawing, all four chambers of the heart contract simultaneously. The right atrium and the left atrium receive blood simultaneously from the vena cava and the pulmonary vein respectively. The right and the left atria (plural for atrium) contract simultaneously to send blood down through the tricuspid valve and the mitral valve respectively. And the right and left ventricles contract simultaneously to push blood up into the pulmonary artery and the aorta respectively. All this without missing a beat. Hey, I told you this was spectacular organ!