Pulmonary artery: anatomy, function and importance

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The main pulmonary artery, also called the pulmonary trunk, is a vessel that exits the heart. It divides into the left and right pulmonary arteries, which carry relatively low-oxygen, high-carbon dioxide blood to the lungs .

There it is replenished with inhaled oxygen, and excess carbon dioxide is "thrown out" and excreted from the body by exhalation.

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Anatomy

The pulmonary trunk and the left and right pulmonary arteries are relatively large arteries. Each of them is shaped like tubes with a lumen (a hole through which blood flows). The left and right pulmonary arteries direct blood to the left and right lungs, respectively.

Composition

The pulmonary trunk and the right and left pulmonary arteries are shaped like a capital T, with the trunk forming the lower portion and the left and right branches each forming one of the two sides in the upper portion.

There is a valve between the right ventricle of the heart and the pulmonary trunk. This valve, which has two cusps of connective tissue, is designed to open when the heart pumps blood so that blood can flow from the right ventricle to the pulmonary trunk. When the heart muscle relaxes, the valves close to prevent blood from returning to the heart.

Like all arteries, the walls of the pulmonary arteries have multiple layers of muscle that allow them to expand (widen) and narrow (narrow). This is very different from vein walls, which are thinner and less muscular.

Most of the arteries in the body carry oxygenated blood, but the pulmonary arteries are one of the two exceptions that carry deoxygenated blood. (Another example is the umbilical arteries, which carry oxygen-requiring blood from the developing baby to the mother.)

Location

The pulmonary trunk, relatively short and wide, is located at the outlet of the right ventricle. This main arterial branch is located above the heart, to the left of the ascending aorta .

The right pulmonary artery fits into the aortic arch , behind the ascending aorta and in front of the descending aorta. The left pulmonary artery runs along the left side of the aorta .

These vessels penetrate the pericardium, the connective tissue that lines the heart. Since the heart is on the left side of the chest, the left pulmonary artery is closer to the lung than the right pulmonary artery.

After the left pulmonary artery enters the left lung, it divides into smaller branches. The right pulmonary artery passes through the upper chest and enters the right lung. The artery then divides into smaller branches.

Anatomical variations

Normally, each pulmonary artery is divided into three to seven branches. The most common anatomical variations in the pulmonary arteries are variations in the number of arterial branches in the lungs. Sometimes one or more sections may branch out before the right or left pulmonary artery enters the heart.

There are also rare congenital deformities of the pulmonary arteries:

  • Pulmonary atresia : This is a condition in which the pulmonary valve does not open properly, resulting in decreased blood flow from the heart to the lungs. Symptoms such as rapid breathing and slow growth in childhood can vary depending on the degree of anatomical deformity. This defect is treated with surgery.
  • Pulmonary artery stenosis : This birth defect is characterized by a narrow pulmonary artery. It can be associated with a variety of heart defects and cause fatigue and shortness of breath, as well as symptoms of any coexisting heart defects. Surgery may involve widening the artery with a stent.
  • Pulmonary artery sling: This is a congenital defect in which the left pulmonary artery branches from the right pulmonary artery rather than directly from the pulmonary trunk. The defect is associated with narrowing of the trachea (windpipe) and bronchi (airways) . A pulmonary artery sling can be treated with surgery.

Function

The pulmonary arteries are part of the pulmonary circulation, which also includes the pulmonary veins and the pulmonary capillaries. The purpose of pulmonary circulation is to transport oxygen and carbon dioxide between the body's blood and the air that is inhaled and exhaled in the lungs.

The special function of the pulmonary arteries is to transport low-oxygen, high-carbon dioxide blood to the pulmonary capillaries in the lungs, where this exchange takes place.

When the blood is oxygenated and cleansed of carbon dioxide, it returns through the pulmonary veins to the right ventricle of the heart. From there, blood is pumped into the left ventricle and eventually spreads through the aorta to arteries that carry oxygen-rich blood throughout the body.

Clinical relevance

There are two main conditions that affect the pulmonary arteries in adults: pulmonary embolism (PE) and pulmonary arterial hypertension. Pulmonary arterial hypertension is a rare condition that develops over time. PD is a blood clot in an artery in the lungs that requires a medical emergency.

Pulmonary embolism

PD is a condition in which a blood clot gets stuck in the pulmonary artery and blocks blood flow to the lungs. Symptoms include:

  • Sudden shortness of breath
  • Chest and back pain
  • Cough
  • Bloody sputum
  • Excessive sweating
  • Daze
  • Blue lips or nails
  • Loss of consciousness

PD can occur when a blood clot forms in a vein (such as in the legs) and travels through the heart and eventually lodges in the pulmonary artery. Risk factors include bleeding disorders, cancer , and prolonged physical immobility.

Pulmonary embolism is a life-threatening medical emergency that must be treated with blood thinners or an interventional procedure.

Pulmonary arterial hypertension

Pulmonary arterial hypertension is a rare type of pulmonary hypertension characterized by narrowing, stiffness, and thickening of the arteries in and around the lungs. This can cause fatigue, shortness of breath, hemoptysis (hemoptysis), and swelling of the legs.

Pulmonary arterial hypertension can develop without a known cause, and risk factors include scleroderma or other connective tissue disorders, exposure to toxins, and cirrhosis of the liver .

The condition progresses and can lead to severe heart failure and disability due to exercise intolerance. Prescription medications can slow the progression of pulmonary arterial hypertension.

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The pulmonary arteries carry blood from the heart to the lungs. These vessels are part of the pulmonary circulation and are influenced by other blood vessels in this system. Congenital heart deformities can be associated with changes in the pulmonary arteries, and these problems may require surgery during childhood.

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