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What is the Cardiovascular System? - Function & Organs

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  • 0:01 Parts of the…
  • 0:30 The Heart
  • 2:51 Pulmonary Circulation
  • 4:00 Systemic Circulation
  • 4:53 Lesson Summary
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Lesson Transcript
Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Your cardiovascular system never stops! Your heart beats many times each minute to circulate blood throughout your body. In this lesson, learn about your heart and the rest of your cardiovascular system.

Parts of the Cardiovascular System

The cardiovascular system is one of the most amazing organ systems in your body. It is always working hard while it circulates blood throughout your body to transport oxygen and carbon dioxide, nutrients, hormones, and cells to all your organs and tissues. It is made up of three main parts: the heart, pulmonary circulation, and systemic circulation. Let's look more closely at each of these parts and see how they all work together to keep your body going.

The Heart

The major organ of the cardiovascular system is the heart. The heart is a muscular organ in the center of your chest that contracts about 60-80 times a minute to pump blood throughout your body.

In humans like you, the heart contains four chambers: two ventricles and two atria, which are separated by valves. Each atrium is a small chamber that collects blood returning to the heart from the systemic or pulmonary circulation, and each ventricle is a larger chamber that pumps blood out into the circulation.

The right atrium and ventricle are separated by the tricuspid valve, which has three flaps and prevents blood from flowing backwards from the right ventricle into the right atrium. On the left side of the heart, the mitral valve is a 2-flapped valve that separates the left atrium and the left ventricle. The heart has a thick wall made mainly of muscle that is constantly contracting and relaxing with every heartbeat throughout your life.

If you could look inside the wall of the heart, you would find three layers of tissue: the endocardium, myocardium, and epicardium. The endocardium is the thin inner lining of the heart wall. To help you remember where the endocardium is located, notice that 'endo' sounds like 'inside,' and the endocardium is inside the heart.

The myocardium is the thick, muscular, middle layer of the heart wall. It is made of many layers of a special type of muscle tissue called cardiac muscle, which is striated, involuntary muscle tissue. Remember that myocardium, muscle, and middle all start with the letter M, so when you think about the muscle in the middle of the heart wall, you will know that it is called the myocardium.

Just like all your muscles, the myocardium uses a lot of oxygen and requires a constant supply of blood. This is provided by the coronary arteries, which are small arteries that supply blood to the heart muscle in the myocardium.

On top of the myocardium on the outside of the heart, there is a layer of protective tissue called the epicardium. Any medical term that includes the prefix 'epi-' will always be talking about something that is on the outside, just like the epidermis is the skin that is on the outside of your body. In this case, the prefix 'epi-' tells you that the epicardium is the layer of tissue on the outside of the heart.

Pulmonary Circulation

Now that we know a bit about the heart, let's look at what happens to your blood after it leaves your heart. The left and right sides of your heart actually have different functions. The right side of the heart pumps blood to the lungs, where it picks up oxygen and loses carbon dioxide. The blood vessels that go between the heart and lungs make up the pulmonary circulation. So, what actually happens during each heartbeat on the right side of the heart?

Deoxygenated blood from the veins in your body enters the right atrium through the vena cava, the largest vein in your body. After passing through the right atrium and ventricle, the blood is pumped into the pulmonary artery, which carries deoxygenated blood to the lungs. The pulmonary artery is special because it is the only artery in your body that carries deoxygenated blood. After blood passes through the lungs, it picks up oxygen from the air and gets rid of the carbon dioxide that was produced by the cells in your body. The pulmonary vein then carries freshly oxygenated blood back to the heart, where it collects in the left atrium. The pulmonary vein is also unique because all of the other veins in your body carry blood that is deoxygenated.

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