Learn From the Expert: How Does the Blood Circulatory System Work

The circulatory system consists of blood vessels, the blood that flows through the heart. Learn more about each in detail here!

Blood flow is life. It is such a crucial aspect of life that you even hear the term lifeblood used to refer to the flow of money or information in an organization.

Learn From the Expert: How Does the Blood Circulatory System Work
The circulatory system, also called the cardiovascular system or the vascular system. Image via Shutterstock

If it is interrupted, the organization – or in our case – our bodies die. But how does the blood circulatory system work?

What Is the Circulatory System?

The circulatory system consists of blood vessels, the blood that flows through them and the heart. Let’s learn more about each in greater detail.

According to Live Science, the average adult’s body contains 4.5 to 5.5 liters of blood, and it accounts for up to ten percent of your body weight[1]. The blood picks up nutrients from the digestive tract like sugar and carries it through the body.

It picks up waste substances that are disposed of in the kidneys, though waste gases like carbon dioxide are taken to the lungs.

The blood takes about a minute to make the full loop through the body. It is traveling at roughly a meter a second as it leaves the heart, though it slows down somewhat when it reaches the capillaries.

The term artery refers to blood vessels that move blood away from the heart. According to the Mayoclinic, Veins refer to blood vessels that move blood toward the heart.

Arteries are shown as red lines on anatomy diagrams to represent the oxygen-rich blood they carry.

Veins are shown as blue lines because they’re carrying oxygen-poor blood back to the heart and lungs. According to the Medicinenet, Capillaries are the small blood vessels that allow the exchange of nutrients and waste products.

The human circulatory system can be divided into several “circuits”.


*All individuals are unique. Your results can and will vary.

  • The pulmonary circuit sends blood between the heart and lungs (source).
  • The coronary circuit contains blood vessels that deliver blood to just the heart (source).
  • The systemic circuit refers to blood vessels that let blood flow to and from the rest of the body (source).

How Does the Heart Work?

The heart is the center of the circulatory system. If it stops, everything else comes to a halt. Your heart pumps the blood to the lungs before circulating it through the rest of the body.

With every beat, the pump pushes blood through the network of veins and capillaries. This allows blood cells to pick up waste from the cells around them and carry them to the kidneys and lungs.

There are four chambers in the heart.

  • The upper two chambers are called the atrium.
  • The lower two chambers are called the ventricles.

The heart also has two sides, left and right.

  • The right atrium brings in oxygen blood and pumps it into the right ventricle.
  • The right ventricle pushes it into the lungs to pick up oxygen and eliminate carbon dioxide.
  • The left atrium pulls in the oxygen-rich blood from the lungs.
  • It is pushed to the left ventricle that then pushes it to the rest of the body.
According to the Mayo Clinic, the average person’s heart rate is between 60 and 100 beats per minute. It beats every moment of your life. Irregular heartbeats and poor blood flow may be signs of cardiac (heart) problems.

You shouldn’t ignore cardiac problems or health problems that adversely impact your cardiovascular system, because your life ends when your heart stops.

Fortunately, Dr. David Nabi can clear blockages and intervene if the issue is caught in time.

How does the heart know to beat?

It is receiving electrical impulses from the nervous system that tell it to do so and how fast. There is a complex interplay of hormones and reflexes.

For example, you’ve probably felt your heart racing after being frightened. The jolt of adrenaline your body put out in response to the perceived threat told the heart to pump faster. That fight-or-flight survival reflex is intended to give your body the ability to move quickly to avoid a threat.

You’ve probably been told to relax and de-stress for your health. This is because stress drives up the heart rate, but unlike jumping out of the way of a speeding car, you don’t have a definite action to burn off that energy.

However, your cardiovascular system benefits from regular exercise, and this can burn off the stress hormones that force the heart to beat harder than it really must.

What you eat and drink can affect your heart rate. Caffeine and stimulants like energy drinks speed it up. Depressants like alcohol and sleeping pills slow it down.


*All individuals are unique. Your results can and will vary.

Dehydration and high salt intake can increase your blood pressure, too. This is why hypertension or high blood pressure may be treated with modifications to your diet.

What Is the Cardiopulmonary System?

If someone has a heart attack, it may be called a cardiopulmonary event. This is because the term cardiopulmonary refers to the combined system of the heart and lungs. And they are closely linked. This is why a heart attack can cause both chest pain and shortness of breath.

Chronic shortness of breath could be a sign of worsening cardiovascular problems, or it could be due to something else. Visit a doctor like David Nabi, MD if you’ve been diagnosed with a narrowing of the arteries or other circulatory problems.

What Are the Symptoms of Problems with the Circulatory System?

A heart attack or heart failure is the worst possible outcome when you’re having circulatory system problems. It doesn’t necessarily come with pain in the chest.

Other symptoms of cardiac problems include chest pressure, coldness in the extremities, weakness in the legs or arms, general pain and numbness.

Many of these symptoms are related to worsening circulation. For example, the coldness and pain are caused by the arms and legs not getting enough oxygen and drowning in their waste products.

According to Harvard Health Publishing, heart problems can cause swollen feet and ankles, as well. That is understandable since poor circulation can result in pooling of blood in the extremities. And your feet are more prone to it since we use our hands even when we’re sitting down.

Any significant cardiovascular problem can contribute to fatigue, unexplained aches and pains, and an erratic heartbeat.

*Note that this doesn’t necessarily mean you are having a heart attack. It can be caused by valve problems, heart rhythm problems, and blood pressure problems.

When to See a Cardiologist

Always discuss these symptoms with a doctor. However, pain and other issues that occur during exercise but disappear with rest warrant a visit with a cardiologist.

There are other issues one can have with the circulatory system. Stiffening blood vessels from age, high cholesterol or diabetes can affect circulation throughout the body.

By the time you have wounds that are slow to heal, the same problem is damaging your kidneys and can lead to blindness. This is why you should consult with a cardiologist if you have chronic high blood pressure or diabetes.

Circulatory problems can be localized, too. Varicose veins are a classic example. The veins range from harmless, unsightly knots in your legs to painful disruptions of normal blood flow that make it difficult to walk. Know that these conditions can be treated by doctors like David Nabi, MD.

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Michelle Routhenstein, MS, RD, CDE, CDN

Michelle is the Owner and President of Entirely Nourished. Her passion is in empowering others to take control of their health to preve

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