Differences between Pulmonary and Systemic Circulation

The heart is one of the most important muscle in a human body. Heart pumps the blood throughout the body of a living being. For the purpose of circulation of blood inside the human body, pulmonary and systemic circulation is used. There are four chambers of a human heart. Two upper atria and two lower ventricles. The key difference in between these two circulations is the carrying of de-oxygenated and oxygenated blood. The right side of the heart which means right atrium and right ventricle are responsible for de-oxygenated blood while the left side is responsible for the oxygenated blood. Systemic circulation carries the oxygenated blood towards different body parts while the pulmonary circulation carries oxygen depleted blood from the heart to the lungs. Both of these are part of cardio-vascular system.

Pulmonary Circulation:

Pulmonary circulation is responsible for carrying the de-oxygenated blood from the heart to the lungs and then brings the oxygenated blood back from the lungs to the heart. The oxygenated blood is then supplied to the whole body through systemic circulation.

Systemic Circulation:

Systemic circulation is responsible for carrying oxygenated blood from the heart to different body parts and then bringing back the deoxygenated blood from the body parts to the heart. Then the deoxygenated blood is send to lungs through pulmonary circulation.


Sir William Harvey presented this theory of circulation of oxygenated blood. The oxygenated blood is in left ventricle and then leaves through the left aorta. Aorta is the largest artery in the human body. The aorta is further divided into arterioles and capillaries which are spread throughout the body for blood circulation. During the systemic circulation, the blood also passes through the kidneys. Kidneys purify the blood as much as it can and then the deoxygenated blood is sent back to heart.

Sir Ibn-al-Nafis presented the theory of circulation of deoxygenated blood. After receiving the deoxygenated blood by the heart, the blood is sent to lungs for purifying it. The lungs oxygenate the blood by taking carbon di oxide through diffusion. Our heartbeats which we listen is due to the opening and closing of ventricles of the heart thus due to systemic circulation.

Both of these circulation systems work together. These systems are inter-connected. They can’t work without each other. Both of them are equally responsible for the blood circulation in the human body.

The systemic circulation deals with the left side of the heart while the pulmonary circulation deals with the right side of the heart.

Now let’s study their course one by one. The systemic circulation starts from the left ventricle. From the left ventricle the blood is transferred to the left aorta. Aorta sends the oxygenated blood to arteries which are divided into arterioles and further divided into capillaries.

The pulmonary circulation starts with the de-oxygenated blood leaving the heart to oxygenate in lungs. After the lungs diffuse the oxygen to the blood and takes the carbon di oxide, the blood re-enters the heart. The whole process of pulmonary circulation is based upon diffusion.

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