Difference Between Pulmonary Artery and Pulmonary Vein

Pulmonary artery

The pulmonary artery is a particular blood vessel that delivers deoxygenated blood (blood with less oxygen content) to the lungs, it pumps blood away from the heart in contrast to veins which deliver blood to the heart.  The difference with respect to other arteries which carry oxygen-rich blood the pulmonary artery transports blood which has less oxygen. 

The artery begins in the heart at the base of the right ventricle and at this point, it is known as the pulmonary trunk which is short and wide structure. The pulmonary trunk branches off in two directions which are the right and left pulmonary artery. The left pulmonary artery is short and it pierces through the sac around the heart which is the protective covering of the heart called pericardium. From there, the pulmonary artery enters the left lung. The right pulmonary artery is longer and travels across the upper chest of the human body and enters the right lung

Pulmonary Artery Function

The right and left pulmonary artery branches bring deoxygenated blood to the corresponding right and left lungs. There, the blood is enriched with oxygen and pumped back into the heart via the pulmonary veins. This oxygen-rich blood flows into the heart's left atrium and is then pumped to the left ventricle. Finally, it is dispersed through the aorta to the arteries which carries the oxygenated blood throughout our body. Normally blood pressure in the pulmonary artery is 18 to 25mm of Hg (systolic pressure at rest). The mean pulmonary pressure ranges from 12 to 16 mm of Hg.

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Pulmonary Vein

There are four pulmonary veins in the body which bring fresh oxygenated blood from the lungs to the left atrium. From the left atrium, the oxygenated blood travels to the left ventricle and from there it is pumped to various parts of the body.

The CO2 rich blood enters the capillaries where the CO2 is removed and O2 is obtained from the alveoli. From capillaries, blood enters bronchial veins and exit the lungs through the region known as the hilum, where both blood vessels and right and left main bronchi enter the lungs in the medial, central area of each lung.

After passing through the hilum, the right pulmonary vein passes posterior to the superior vena cava and right atrium to enter into the left atrium. The left pulmonary vein then passes in front of the descending aorta entering the left atrium.

Pulmonary Vein Function

Unlike other veins, pulmonary veins carry oxygenated blood from the lungs and back to the left atrium of the heart so it can be pumped to different parts of the body.

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The differences between pulmonary and systemic circulation are below:

Difference between Pulmonary and Systemic Circulation


Pulmonary circulation

Systemic circulation


Thin vessels with minimal smooth muscle. The vessels are dependent on alveolar pressure.

Thick vessels with abundant thick smooth muscle. The vessels are embedded in tissues.

Blood volume

Approximately 500ml in a 70Kg person.

Approximately 4500 in a 70kg person.

Reservoir function

10% of the total blood volume is circulated via the system.

90% of the total blood volume is circulated through this system.

Blood pressure

18-25 mm of Hg for normal PA Systolic pressure.

8-15 mm of Hg for normal PA of Diastolic pressure.

120mm of Hg for normal PA systolic pressure.

80mm of Hg for normal PA diastolic pressure.

Circulatory regulation

Minimum capacity to actively regulate or control blood flow, except via hypoxic pulmonary vasoconstriction.

Regional blood flow regulation is carried out at the level of arterioles.

Synthetic functions

It is the source of thromboplastin and heparin which can degrade filtered clots.

Synthesis of nitric oxide, as well as pro and anti-coagulants

What Is The Function of The Aorta?

The aorta is a major part of the systemic circulation and pumps blood to the entire body except for the respiratory area of the lung. It also regulates the blood flow and velocity within vessels. Aorta functions are:

  • Branches of ascending aorta supply blood to the heart.

  • Branches of the aortic arch supply blood to the head, neck and arms. 

  • Branches from the thoracic descending aorta supply blood to the chest, excluding the heart and the respiratory zone of the lung.

  • Branches from the abdominal aorta supply blood to the abdomen.

The differences between pulmonary arteries and pulmonary veins are explalined below:

Differentiate between Pulmonary Artery and Pulmonary Vein

Pulmonary arteries

Pulmonary veins

There’s one pair of pulmonary arteries branching out from the pulmonary aorta.

There are two pairs of pulmonary veins with one pair branching out from each lung.

The pair of pulmonary arteries take blood away from the heart to the lungs of the respective side.

The two pair of pulmonary veins carry oxygen-rich blood from the lungs to the heart.

Blood in pulmonary arteries is deoxygenated.

Blood in pulmonary veins is oxygenated.

Pulmonary arteries carry the blood from the right ventricle of the heart.

Pulmonary veins carry blood towards the left auricle of the heart.

Blood pressure is higher in pulmonary arteries.

Blood pressure is lower compared to pulmonary veins.

The walls of the pulmonary arteries are thick and elastic.

The walls of the pulmonary veins are thinner compared to pulmonary arteries.

The difference between arteries and pulmonary arteries are below:

Difference between Arteries and Pulmonary Arteries



Pulmonary arteries


Thick-walled blood vessels which supply oxygenated blood to all parts of the body.

Thick-walled blood vessels that carry blood with less oxygen to the lungs. 


Transports oxygen-rich blood to the entire body.

Supplies blood with CO2 to lungs for purification.


Arteries are present over the heart.

Pulmonary arteries originate from the pulmonary trunk towards the right ventricle beneath the aorta artery.

Type of circulation

Arteries perform systemic circulation.

These arteries perform pulmonary circulation.

FAQ (Frequently Asked Questions)

1. What is the function of the aorta in the heart?

A: The aorta is the primary and the largest artery of the human body that transports blood away from the heart to the rest of the body. After the blood is carried out from the heart through the aortic valve, it travels across the aorta, making a cane-shaped curve which connects with other major arteries to deliver oxygenated blood to the brain, muscles, and other cells. By doing this, the aorta takes part in the systemic blood circulation in the body. 

  • The ascending aorta supplies blood to the heart.

  • The aortic heart supplies blood to the left side of the brain and neck and the left arm

  • The descending aorta supplies blood to oesophagus, pericardium, diaphragm, lump nodes, ribs and some structures of the heart.

  • The abdominal aorta carries blood to several parts of the body which includes

    • The liver

    • Diaphragm,

    • Stomach

    • Spleen

    • Abdominal oesophagus

    • Intestines

    • Kidneys

    • Spinal cord

    • Pancreas.

2. What is the primary function of the pulmonary artery?

A: The pulmonary arteries bring blood with less oxygen content to the lungs where the blood is enriched with oxygen and it is transported back into the heart with the help of the pulmonary veins. This oxygenated blood travels into the heart's left atrium and is then pumped to the left ventricle. Then it is circulated through the aorta to the arteries which carry it throughout all parts of the human body.