The Anatomy of the Pulmonary Artery

Heart illustration with the pulmonary artery labeled Images

The pulmonary artery is a blood vessel which delivers deoxygenated blood to the lungs. Like all arteries, the pulmonary artery pumps blood away from the heart—in contrast to veins, which deliver blood to the heart. However, unlike most arteries, which carry blood with a relatively high oxygen content, the pulmonary artery transports blood whose oxygen content is relatively low. Blood with little oxygen content is delivered to the lungs via the pulmonary artery. In the lungs, the blood takes on oxygen and then is pumped back to the heart to be circulated throughout the rest of the body.

Anatomy of the Pulmonary Artery

The pulmonary artery begins in the heart at the base of the right ventricle. At this point, it is known as the pulmonary trunk, which is relatively short and wide. As it leaves the heart, the pulmonary trunk branches off in two directions –the left and right pulmonary artery. The left pulmonary artery is short and pierces through the sac around the heart called the pericardium. From there, it enters the left lung. The right pulmonary artery is longer and courses across your upper chest to enter the right lung.

Function of the Pulmonary Artery

The left and right pulmonary artery branches bring their deoxygenated blood to the corresponding left and right lungs. There, the blood is enriched with oxygen and pumped back into your heart via the pulmonary veins. This freshly oxygenated blood flows into your heart's left atrium, is pumped to the left ventricle, and then finally dispersed through the aorta to the arteries which carry the oxygen-rich blood throughout our body. 

The pulmonary artery is one of the few arteries which transports oxygen-low blood and the pulmonary veins are among the few veins which deliver oxygen-rich blood. Most of us learned in school that arteries carry oxygen-rich blood to the body. But the pulmonary arteries carry blood that is deficient of oxygen to the lungs. There, they turn into capillaries and surround the alveolii in the lungs, and oxgenation takes place.

Clinical Significance

As a major blood vessel, any vascular disease or condition which might affect smaller vessels are more severe in the pulmonary artery. One such condition which affects the pulmonary blood vessels, particularly the arteries, is pulmonary hypertension, or high blood pressure.

Pulmonary arterial hypertension is caused by, and contributes to, a narrowing, stiffening, and thickening of the arteries in and around our lungs. With diminished blood flow capacity in our arteries, our heart must work harder to pump sufficient blood to our lungs. Decreases in blood flow lead to less oxygen delivered throughout our bodies, which has a cumulative negative effect on our vascular, pulmonary, and neurological health. Therefore, pulmonary arterial hypertension is a serious cause for concern.

Risk factors for hypertension include:

  • Obesity
  • Lack of exercise
  • Prolonged periods of stress
  • Depression
  • Smoking
  • Recreational drug use
  • Advanced age
  • Family history of hypertension or heart disease

Pulmonary arterial hypertension and the risk factors that lead to it also increase the likelihood of developing other conditions, such as hypertrophy of the right ventricle, pulmonary embolism, pulmonary fibrosis, and stroke.

Note that pulmonary hypertension can affect both sides of the heart. Arterial hypertension affects the right side; it relates to poor vascular health in the arteries in and around the lungs. Hypertension on the left side of our heart relates less to blood vessels, and more to the failure of the heart's left chambers to pump blood efficiently. This can lead to other conditions, such as a pooling of blood in the lungs, pulmonary edema, and pleural effusions. However, pulmonary hypertension on either side of our heart has the same risk factors. Therefore, if the risk factors characterize you, lifestyle changes can lead to corresponding improvements in your overall health.

A pulmonary embolus is a condition where a blood clot lodges in the pulmonary artery. Most often, this clot gets stuck in the bifurcation of the pulmonary artery where the right and left artery branches out. The clot can block blood flow to the lungs and pool blood in the heart. This creates a medical emergency, and it may lead to significant medical problems including death. A pulmonary emoblus is a medical emergency. Often pulmonary embolii (the plural form of "embolus") form as deep vein clots in the lower legs. Signs of a deep vein thrombosis (DVT) or clot include:

  • Calf pain
  • Redness in your calf and foot
  • Swelling of your lower calf and foot
  • Difficulty walking due to pain

If you have any of these symptoms, see your doctor; he or she can perform the necessary tests to determine if you have a DVT. Treatment involves taking medicines to thin the blood and prevent the clot from travelling to your heart and your pulmonary artery.

A Word From Verywell

The pulmonary artery is a very important structure that is responsible for carrying blood from your heart to your lungs. This blood is deficient of oxygen, and it travels to the lungs to become oxygen-rich blood. Having an understanding of the structure and function of the pulmonary arteries can help you understand problems that may occur with them.

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Article Sources

  • "Guidelines for the diagnosis and treatment of pulmonary hypertension. The Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS)." Nazzareno Galiè, Marc Humbert, Jean-Luc Vachiery, Simon Gibbs, Irene Lang, Adam Torbicki, Gérald Simonneau, Andrew Peacock, Anton Vonk Noordegraaf, Maurice Beghetti, Ardeschir Ghofrani, Miguel Angel Gomez Sanchez, Georg Hansmann, Walter Klepetko, Patrizio Lancellotti, Marco Matucci, Theresa McDonagh, Luc A. Pierard, Pedro T. Trindade, Maurizio Zompatori and Marius Hoeper. Eur Respir J 2015; 46: 903-975.