Blood Flow - How the Heart Works - Blood Flow

Arteries and veins link your heart to the rest of the circulatory system. Veins bring blood to your heart. Arteries take blood away from your heart. Your heart valves help control the direction the blood flows.

Heart valves
- How the Heart Works - Blood Flow

Heart valves control the flow of blood so that it moves in the right direction. The valves prevent blood from flowing backward.

The heart has four valves.

  • The tricuspid valve separates the right atrium and right ventricle.
  • The mitral valve separates the left atrium and left ventricle.
  • The pulmonary valve separates the right ventricle and the pulmonary artery.
  • The aortic valve separates the left ventricle and aorta.

The valves open and shut in time with the pumping action of your heart's atria and ventricles. The opening and closing involves a set of flaps called cusps or leaflets. The cusps open to allow blood to flow out of a chamber and close to allow the chamber to refill with blood. Heart valve diseases can cause backflow or slow the flow of blood through the heart.

Valves of the heart. Two valves sit like doors between your atria and ventricles to prevent blood from flowing backward into your atria. The tricuspid valve opens into your right ventricle, and the mitral valve opens into your left ventricle. Strong thin tissues called chordae tendineae hold your valves in place during the forceful contractions of your ventricles. Blood leaving the ventricles passes through another set of valves, the pulmonary valve, between your right ventricle and pulmonary trunk, and the aortic valve, connecting your left ventricle and aorta. Medical Animation Copyright © 2019 Nucleus Medical Media, All rights reserved.

Adding oxygen to blood
- How the Heart Works - Blood Flow

Oxygen-poor blood from the body enters your heart through two large veins called the superior and inferior vena cava. The blood enters the heart's right atrium and is pumped to your right ventricle, which in turn pumps the blood to your lungs.

The pulmonary artery then carries the oxygen-poor blood from your heart to the lungs. Your lungs add oxygen to your blood. The oxygen-rich blood returns to your heart through the pulmonary veins. Visit our How the Lungs Work Health Topic to learn more about what happens to the blood in the lungs.

The oxygen-rich blood from the lungs then enters the left atrium and is pumped to the left ventricle. The left ventricle generates the high pressure needed to pump the blood to your whole body through your blood vessels.

When blood leaves the heart to go to the rest of the body, it travels through a large artery called the aorta. A balloon-like bulge, called an aortic aneurysm, can sometimes occur in the aorta.

Circulation and the heart. Your heart is divided into left and right halves, which work together like a dual pump. On the right side of your heart, oxygen-poor blood from your body’s tissues flows through large veins, called the superior and inferior vena cava, into your right atrium. Next, the blood moves into your right ventricle, which contracts and sends blood out of your heart to your lungs, to gather oxygen and get rid of carbon dioxide. On the left side of your heart, oxygen-rich blood from your lungs flows through your pulmonary veins into your left atrium. The blood then moves into your left ventricle, which contracts and sends blood out of your heart through the aorta to feed your cells and tissues. Medical Animation Copyright © 2019 Nucleus Medical Media, All rights reserved.

Supplying oxygen to the heart’s muscle
- How the Heart Works - Blood Flow

Like other muscles in the body, your heart needs blood to get oxygen and nutrients. Your coronary arteries supply blood to your heart. These arteries branch off from the aorta so that oxygen-rich blood is delivered to your heart as well as the rest of your body.

  • The left coronary artery delivers blood to the left side of your heart, including your left atrium and ventricle and the septum between the ventricles.
  • The circumflex artery branches off from the left coronary artery to supply blood to part of the left ventricle.
  • The left anterior descending artery also branches from the left coronary artery and provides blood to parts of both the right and left ventricles.
  • The right coronary artery provides blood to the right atrium and parts of both ventricles.
  • The marginal arteries branch from the right coronary artery and provide blood to the surface of the right atrium.
  • The posterior descending artery also branches from the right coronary artery and provides blood to the bottom of both ventricles.

Arteries supplying oxygen to the body. The coronary arteries branch off the aorta and supply the heart muscle with oxygen and nutrients. At the top of your aorta, arteries branch off to carry blood to your head and arms. Arteries branching from the middle and lower parts of your aorta supply blood to the rest of your body. Medical Animation Copyright © 2019 Nucleus Medical Media, All rights reserved.

Some conditions can affect normal blood flow through these heart arteries. Examples include:

The coronary veins return oxygen-low blood from the heart's muscles back to the right atrium so it can be pumped to the lungs. They include:

  • The anterior cardiac veins.
  • The great cardiac vein.
  • The middle cardiac vein.
  • The small cardiac vein.