Difference Between Pulmonary and Systemic Circulation

Main Difference – Pulmonary vs Systemic Circulation

In mammals, the circulation occurs in two circuits, and blood is circulated through the heart for two times. This type of circulation is called the double circulation. Pulmonary and systematic circulation are the two types of circulations that occur in a double circulation system. The difference between pulmonary and systemic circulation stems from the nature of the blood and the destination of the blood. The main difference between pulmonary and systematic circulation is that pulmonary circulation carries deoxygenated blood from heart to lungs and oxygenated blood back to the heart whereas systemic circulation carries oxygenated blood from the heart throughout the body and deoxygenated blood back to the heart.

Key Areas Covered

1. What is Pulmonary Circulation
      – Definition, Circulation Pathway, Importance
2. What is Systemic Circulation
      – Definition, Circulation Pathway, Importance
3. What are the Similarities Between Pulmonary and Systemic Circulation
      – Outline of Common Features
4. What is the Difference Between Pulmonary and Systemic Circulation
      – Comparison of Key Differences

Key Terms: Aorta, Double Circulation, Heart, Inferior Vena Cava, Lungs, Pulmonary Artery, Pulmonary Circulation, Pulmonary Vein, Superior Vena Cava, Systemic CirculationDifference Between Pulmonary and Systemic Circulation - Comparison Summary

What is Pulmonary Circulation

Pulmonary circulation is the circulation system that carries deoxygenated blood to the lungs and returns oxygenated blood from the lungs back to the heart. The two blood vessels involved in the pulmonary circulation are pulmonary artery and the pulmonary vein. The deoxygenated blood flows into the right ventricle from the right atrium. This blood is carried to the alveoli of lungs for the oxygenation by the pulmonary artery. The pulmonary artery, which immediately originates from the right ventricle, is called the pulmonary trunk. The pulmonary trunk divides into two; the left pulmonary artery and the right pulmonary artery. The left pulmonary artery carries blood to the left lung while the right pulmonary artery carries blood to the right lung.

Difference Between Pulmonary and Systemic Circulation

Figure 1: Pulmonary Circulation

Carbon dioxide is removed from the blood while oxygen is taken into the blood at the alveolar capillaries. The oxygenated blood is carried to the left atrium of the heart by four pulmonary veins. A small amount of oxygenated blood is carried to the heart by the bronchial veins. 

What is Systemic Circulation

The systemic circulation is the circulation system that carries oxygenated blood throughout the body and returns the deoxygenated blood to the heart from the body tissues. The oxygenated blood from the lungs returns to the left atrium of the heart through pulmonary veins. This blood flows into the left ventricle and comes out from the heart through the aorta. The aorta branches into small arteries, which carry blood to different organs in the body. Within an organ or tissue, these arteries branch to arterioles, which make blood capillaries. The exchange of oxygen and nutrients with the metabolizing cells occurs via blood capillaries.

Main Difference - Pulmonary vs Systemic Circulation

Figure 2: Pulmonary and Systemic Circulation

Carbon dioxide and other metabolic wastes are transported back to the blood. The deoxygenated blood drains back to the venules and returns to the right atrium of the heart by vena cava. The deoxygenated blood from the upper half of the body above the diaphragm drains by the superior vena cava while the deoxygenated blood from the lower half of the body drains by the inferior vena cava. 

Similarities Between Pulmonary and Systemic Circulation

  • Both pulmonary and systemic circulation are the components of the double circulation.
  • Both pulmonary and systemic circulation occur in many mammals.
  • Both pulmonary and systemic circulation are types of closed circulation systems.
  • Both pulmonary and systemic circulation comprise arteries and veins.
  • Both pulmonary and systemic circulation help to reach respiratory gases, nutrients, and metabolic wastes to their final destinations.

Difference Between Pulmonary and Systemic Circulation

Definition

Pulmonary Circulation: Pulmonary circulation refers to the passage of blood from the right ventricle of the heart to the lungs, where the blood gets oxygen, remove carbon dioxide and return to the right atrium of the heart.

Systemic Circulation: Systemic circulation refers to the passage of blood from the left ventricle of the heart to the rest of the body through systemic arteries, carrying oxygen and nutrients to the cells and return to the left atrium of the heart by superior and inferior vena cava.

From the Heart

Pulmonary Circulation: Pulmonary circulation carries deoxygenated blood from the right ventricle of the heart to the lungs through the pulmonary artery.

Systemic Circulation: Systemic circulation carries oxygenated blood from the left ventricle of the heart to the rest of the body by the aorta.

To the Heart

Pulmonary Circulation: Pulmonary circulation carries oxygenated blood from the lungs to the left atrium of the heart by the pulmonary vein.

Systemic Circulation: Systemic circulation carries deoxygenated blood from the body to the right atrium of the heart by the superior and inferior vena cava.

Composed of

Pulmonary Circulation: Pulmonary circulation is composed of pulmonary artery and pulmonary vein.

Systemic Circulation: Systemic circulation is composed of inferior and superior vena cava, aorta, and other small blood vessels.

Destination of the Blood

Pulmonary Circulation: Pulmonary circulation carries blood to the lungs.

Systemic Circulation: Systemic circulation carries blood throughout the body.

Function

Pulmonary Circulation: Pulmonary circulation helps to release carbon dioxide from the blood while dissolving oxygen in the blood.

Systemic Circulation: Systemic circulation helps to provide nutrients and oxygen to the metabolizing cells in the body.

Conclusion

Pulmonary and systemic circulation are two types of circulations that maintain the homeostasis in the body of many mammals. The pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns to the heart. The systemic circulation carries that oxygenated blood from the heart to the rest of the body and returns the deoxygenated blood back to the heart. The main function of the pulmonary circulation is to oxygenate the blood while the main function of the systemic circulation is to distribute oxygen and nutrients throughout the body while removing the metabolic wastes. This is the difference between pulmonary and systematic circulation.

Reference:

1. “Pulmonary Circulation.” IvyRose Holistic Health and Well-Being, Available here. Accessed 29 Aug. 2017.
2.“Systemic circulation.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 28 May 2008, Available here. Accessed 29 Aug. 2017.

Image Courtesy:

1. “Illu pulmonary circuit” (Public Domain) via Commons Wikimedia
2. “2101 Blood Flow Through the Heart” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things

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