What is the Pulmonary Artery?

Samantha Savage Grace, Lori Holloway
  • Author
    Samantha Savage Grace

    Samantha has taught science, mathematics, and engineering for over 5 years. They have a Master's in the Art of Teaching with a focus in inclusive and equitable STEM education from Goucher College and a Bachelor's in Biology from University of Maryland Baltimore County with minors in Psychology and Emergency Health Services. In addition to teaching licenses in multiple disciplines they also hold certifications through Project Lead the Way for engineering and are AVID certified.

  • Instructor
    Lori Holloway
What is the pulmonary artery? Learn to define pulmonary artery. Learn the anatomy and function of the pulmonary artery. Learn about the branches of the pulmonary artery. Updated: 07/24/2021

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What is the Pulmonary Artery?

The pulmonary arteries are a pair of blood vessels that transport deoxygenated blood from the heart to the lungs. The pulmonary arteries are considered ''great vessels'' and are unique because they are the only arteries in the body that carry deoxygenated blood. They are essential to our cardiovascular system in that they allow deoxygenated blood pulled from the tissues to once again become oxygenated by gas exchange in the lungs. Without these vessels deoxygenated blood would be unable to become oxygenated once again and life would be unsustainable.

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Pulmonary Artery Anatomy

The main pulmonary artery, also known as the pulmonary trunk, originates at the right ventricle at the point of the pulmonary valve, a one-way semilunar valve that allows blood to flow from the right ventricle and into the pulmonary trunk. From there the pulmonary trunk moves superiorly before bifurcating directly below the aortic arch. After bifurcating the vessel becomes the right pulmonary artery and left pulmonary artery. The right pulmonary artery travels to the right lung while the left pulmonary artery travels to the left lung. Once the pulmonary arteries reach the lungs they begin to divide into smaller and smaller vessels, eventually becoming capillary beds in alveoli allowing gas exchange. The right pulmonary artery is longer than the left pulmonary artery.

The pulmonary artery vessels are comprised of three layers of tissue. The outermost layer is the tunica adventitia, it is made mostly of connective tissues and provides support. The tunica media is the middle layer of the vessel, it is the thickest layer and comprised mostly of smooth muscle capable of regulating blood flow. Finally, the innermost layer is called the tunica intima, it is a thin layer made of a single layer of endothelium and connective tissue matrix.

Pulmonary Artery Location

The pulmonary trunk, or main pulmonary artery, begins at the pulmonary valve of the right ventricle. From there it stretches toward the head before branching into the left and right pulmonary arteries just below the aortic arch. After splitting the right pulmonary artery travels horizontally and perpendicularly to the pulmonary trunk. It is located anteriorly to the right bronchus and posteriorly to the superior vena cava before it merges into the superior lobe of the right lung. From the pulmonary trunk the left pulmonary artery arches slightly upward before moving laterally towards the right lung, it is substantially shorter than the left pulmonary artery and quickly meets the superior lobe of the right lung. The pulmonary arteries are located within the lower mediastinum of the thoracic cavity.

Pulmonary Artery Branches

Of the two branches of the pulmonary arteries the right is longer and travels in a nearly perpendicular line to the pulmonary trunk. Conversely, the right pulmonary artery is short and arches before reaching the right lung. When the right pulmonary artery is about to enter the superior lobe of the right lung it divides into the right upper lobar artery and the right descending interlobar artery. The right upper lobar artery supplies blood to the superior lobe of the right lung while the right descending interlobar artery provides blood to the middle lobe and inferior lobe. The left pulmonary artery also branches as it reaches the left lung, however the branching pattern is far more varied than the right. Generally, there are between three and five divisions supplying blood to the upper lobe. The left lung lacks a middle lobe, but the branches supplying blood to the inferior lobe are still often referred to as left descending interlobar arteries.

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Frequently Asked Questions

Where is main pulmonary artery?

The main pulmonary artery, also known as the pulmonary trunk, begins at the pulmonary valve of the right ventricle. From there it travels superiorly before branching directly below the aortic arch into the left and right pulmonary arteries.

What are pulmonary arteries?

The pulmonary arteries are great vessels responsible for transporting deoxygenated blood from the heart to the lungs in order to become oxygenated once again. They are the only arteries that carry deoxygenated blood.

What is the main function of left pulmonary artery?

The main function of the left pulmonary artery is to take unoxygenated blood from the pulmonary trunk and transport it to the left lung where the blood vessel then branches into the lungs and gas exchange takes place, re-oxygenating the blood.

What is the function of pulmonary artery?

The function of the pulmonary arteries is to transport deoxygenated blood from the heart to the lungs where it can once again become oxygenated.

What is the structure of the pulmonary artery?

The pulmonary artery is comprised of 3 layers, the tunica adventitia, the tunica media, and the tunica intima. The tunica adventitia is the outmost layer, it is made mostly of connective tissue as serves a supportive function. The tunica media is the middle layer, it is the thickest and made mostly of smooth muscle that can contract or relax to control blood flow. The inner layer is the tunica media, it is a very thin layer comprised of a single layer of endothelium attached to a connective tissue matrix.

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