How Does Blood Flow Through The Heart?

You know enough about your heart to know that if it stops working, you stop working. All the blood in your body is circulated by the heart, and your blood keeps the oxygen getting to your individual cells. We also know that your heart acts like a pump that keeps all this going on whether you are awake or asleep.

How Does Blood Flow Through The Heart?

It is a muscle

The heart is a muscle like every other muscle in your body, though it is by far the most important one. It expands and contracts, which is the reason it is often referred to as your body’s pump. The expansion and contraction is what causes the blood to flow through the heart and to the veins and arteries, which are the delivery system of blood to your body.

There is a lot more going on than just simple expansion and contraction because your body has to know what blood is allowed to come into the heart and what blood needs to be pushed out from the heart to deliver oxygen. So we will take a closer look at exactly how the heart gets the blood to flow through the heart.

Your heart is divided into two sides – the left and the right. Each side has an upper part and lower part for each side called chambers. The top chambers, each called an atrium, is the holding place for blood that enters into the heart. The bottom chambers, called ventricles, are where blood is moved to be pumped throughout the body.

The Question

The logical question is how does blood get into the heart to be pumped around? There are several major arteries that bring blood to the heart, the largest one called the aorta. The most important one, the pulmonary artery, delivers the blood to your lungs so it can get the oxygen necessary to keep your cells oxygenated.

Veins are the delivery system for the oxygenated blood to be delivered to your heart. The pulmonary vein is the major vein that brings the blood to the heart and fills the lower ventricles.

In case you were wondering, all blood is red. If you look at the veins in your body through the skin they look bluish or purplish, but that is because the light has to go through the skin, and the reflected color is blue or purple.

So the basic process is: 

  • Your atria fill with blood
  • The pulmonary vein delivers the blood to your lungs to be oxygenated
  • The blood is sent to the ventricles for distribution
  • The blood is delivered mainly by the aorta

How Does The Blood Flow Through The Heart?

The question then comes up – why are there two atria and two ventricles? One of the most fascinating things about your body is that it has almost two identical halves. If you cut your body in half from top to bottom, you see they are almost mirror images of each other (two lungs, two legs, two arms, two eyes, etc.). The heart has the same basic design for a reason.

A great example of this is when a person has a heart attack. While a severe heart attack can kill a person, you can have a heart attack and survive. The reason is that your heart has the two sides that are identical. You can have a heart attack on the right side of your body, but the left side will continue to work. You can think of the design of the heart as having a backup system.

Do you remember at the beginning when we said the heart was a muscle? The muscles in our bodies, whether they are in our arms or fingers, expand and contract either voluntarily (like when we open our eyes) or involuntarily, as in the case of your heart. The expansion and contraction happens because signals are sent by our brain to the heart. Your heartbeat is the sound of the expansion and contraction.

There is one final piece of information that has been left out. How does the heart prevent blood from backing up into itself? Inside each chamber of the heart are valves that open and close to direct the blood to where it needs to go. Valves in the atria do not allow blood from the ventricle to reverse flow. The valves in the ventricles are a one way river to the rest of your body.

Think of it as a garden hose turned on to the max. Try putting your thumb over the end of the hose to prevent the water from coming out. The pressure does not allow you to force the water backwards. In your heart, the valves open and close very quickly to prevent the blood flow from reversing direction.


As you can see, there are many things large and small that go on to allow blood to flow through your heart. The main reason blood flows through your heart is to keep it oxygenated and returned to the rest of the body. All the separate parts of the heart work together in sync to keep blood flowing, cells healthy, and muscles functioning.

You should now know what the first muscle in your body to get oxygenated.

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