Pulmonary Arteries


What are the pulmonary arteries?

Your pulmonary arteries are blood vessels that carry oxygen-poor blood from the right side of your heart to your lungs. In medical terms, the word “pulmonary” means something that affects your lungs.

You have one main pulmonary artery, also known as your pulmonary trunk. This artery directly connects with your heart at your pulmonary valve. This is the “door” that controls blood flow out of your lower right heart chamber (right ventricle). After leaving your heart, your main pulmonary artery divides into your right pulmonary artery and left pulmonary artery. Your right and left pulmonary arteries lead to your right lung and left lung, respectively.

You may hear your healthcare provider call your pulmonary artery a “great vessel.” That’s because researchers consider your main pulmonary artery to be one of the great vessels of the heart. Each of these major blood vessels connects with a different chamber of your heart and manages blood flow either in or out of your heart.

Your main pulmonary artery and your aorta are the two great vessels that carry blood out of your heart. A crucial difference is that your pulmonary artery carries oxygen-poor (deoxygenated) blood, while your aorta carries oxygen-rich (oxygenated) blood. In fact, your pulmonary arteries are the only arteries in your body that carry oxygen-poor blood.

Illustration showing the anatomy of your pulmonary arteries, which carry oxygen-poor blood from your heart to your lungs.

Your pulmonary arteries carry oxygen-poor blood from your heart to your lungs.


What does the pulmonary artery do?

Your pulmonary arteries carry oxygen-poor blood from your heart to your lungs. This is a vital function. Your blood needs to reach your lungs to gain oxygen and get rid of waste products like carbon dioxide. This blood then returns to your heart, and your heart pumps it out to the rest of your body.

What role do the pulmonary arteries play in the circulatory system?

Your pulmonary arteries do important work for your circulatory system. Specifically, they support the part known as your pulmonary circuit. This is the network of blood vessels responsible for sending blood back and forth between your heart and lungs. The many parts of your pulmonary circuit work together as a team to provide oxygen to your blood and remove waste products. Here’s a step-by-step breakdown of that teamwork.

  1. Right ventricle: Your heart’s bottom right chamber (right ventricle) pumps oxygen-poor blood through your pulmonary valve into your main pulmonary artery.
  2. Main pulmonary artery: Your main pulmonary artery exits your heart at your pulmonary valve. It then splits (bifurcates) into your right pulmonary artery and left pulmonary artery.
  3. Right and left pulmonary arteries: Your right pulmonary artery goes to your right lung. Your left pulmonary artery goes to your left lung. In your lungs, your pulmonary arteries divide into many smaller blood vessels. Eventually, these smaller vessels lead to capillaries that surround alveoli (air sacs). This is where gas exchange takes place.
  4. Lungs: In your lungs, your blood refills its oxygen supply and gets rid of carbon dioxide.
  5. Pulmonary veins: Your pulmonary veins do the opposite job of your pulmonary arteries. They collect oxygen-rich blood and carry it from your lungs to your heart. This blood empties into your heart’s top left chamber (left atrium).
  6. Left atrium: Your left atrium sends this oxygen-rich blood to your heart’s bottom left chamber (left ventricle).
  7. Left ventricle: Your left ventricle pumps the oxygen-rich blood through your aortic valve and into your aorta. Once your blood enters your aorta, it begins its journey through your systemic circuit. This is the part of your circulatory system that carries blood throughout your body. After delivering oxygen to your organs and tissues, this blood returns to your heart’s right atrium. From there, it flows into your right ventricle and begins the pulmonary circuit all over again.


Where are the pulmonary arteries located?

Your pulmonary arteries are located in your chest cavity. Your main pulmonary artery (pulmonary trunk) connects to your right ventricle at your pulmonary valve at the front of the heart. From there, it leaves your heart and travels upward along the left side of your ascending aorta. Beneath your aortic arch, your main pulmonary artery splits into the right pulmonary artery and left pulmonary artery. These arteries then travel to each of your lungs.

How big are the pulmonary arteries?

Your main pulmonary artery is usually around 5 centimeters (cm) long. Its average diameter is 2.7 cm in people assigned female at birth (AFAB) and 2.9 cm in people assigned male at birth (AMAB).

What are the pulmonary arteries made of?

Like other large and medium size arteries, the walls of your pulmonary arteries are made of three layers:

  • Tunica intima, a smooth inner layer.
  • Tunica media, a middle layer that pushes blood through.
  • Tunica adventitia, a protective outer layer.

Conditions and Disorders

What common conditions and disorders affect the pulmonary arteries?

The most common problems that affect the pulmonary arteries are congenital heart defects. These issues are present at birth.

Congenital heart conditions that may affect your pulmonary arteries include:

Conditions that can affect adults’ pulmonary arteries include:


How can I protect my heart and pulmonary arteries?

Many conditions that affect your pulmonary arteries are present at birth. While you can’t prevent congenital diseases, there are other diseases that you should manage well to prevent the development of pulmonary hypertension. These include:

In addition, you can take the following actions to support your heart health:

When should I talk to a doctor?

Call your healthcare provider if you experience:

A note from Cleveland Clinic

Your pulmonary arteries carry oxygen-poor blood from your heart to your lungs. They’re a vital part of your circulatory system. But because you can’t see them, it can be easy to forget they’re working hard every day.

That’s why it’s helpful to learn your pulmonary artery anatomy along with the lifestyle changes you can make to support your heart and blood vessels. Learning how your body works can help make the invisible become visible. Ask your healthcare provider what you can do to keep your pulmonary arteries and circulatory system healthy.

Last reviewed by a Cleveland Clinic medical professional on 10/29/2022.


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