Difference Between Open Circulatory System and Closed Circulatory System

The key difference between open circulatory system and closed circulatory system is that in open circulatory system, blood and interstitial fluid mix with each other while in closed circulatory system, blood and other fluids never mix with each other.

Open circulatory system and closed circulatory system are two ways in which the circulatory system is functioning in human and other animals. For normal body functions, and to distribute nutrients and other materials throughout the body, most animals require having a circulatory system in place. This could be either an open or a closed circulatory system. The most basic organisms have a rudimentary system of circulation which is beyond the scope of this article. Complex organisms, like animals and humans, have either a closed or an open circulatory system that readily pumps the blood throughout the organism and removes the waste from the body. This particular article contains the facts that emphasize the difference between open circulatory system and closed circulatory system seen in organisms.

CONTENTS

1. Overview and Key Difference
2. What is Open Circulatory System
3. What is Closed Circulatory System
4. Similarities Between Open Circulatory System and Closed Circulatory System
5. Side by Side Comparison – Open Circulatory System vs Closed Circulatory System in Tabular Form
6. Summary

What is Open Circulatory System?

Open circulatory system is one of the circulatory systems found in the two largest phyla; Arthropoda and Mollusca. In comparison to the closed circulatory system, open circulatory system is less complex. Here, heart pumps blood into open cavities from where the blood vessels carry it to all parts of the body bathing all organs that come in its path. There are no arteries to increase blood pressure, and hence, such animals have more blood at low pressure.

Furthermore, the organisms those posses an open circulatory system have blood mixed with the interstitial fluid. Hence, we call this blood as hemolymph, and this blood is not pure as in the organisms which have a closed circulatory system. Moreover, this blood is a mixture of blood and interstitial fluid.

What is Closed Circulatory System?

Closed circulatory system is one of the advanced circulatory systems possessed by vertebrates and few invertebrates. In a closed system, blood remains within a network of vessels and does not leave it or fill the body cavities. Thus, the organs do not get bathed by the blood unlike in the organisms those have an open circulatory system. Closed circulatory system consists of a true heart and the blood vessels such as veins, capillaries and arteries. Therefore, blood never mixes with other fluids. Hence, it remains as true blood which is pure. Furthermore, heart pumps blood with pressure in order to supply for all body parts.

Besides, there exist two circulatory pathways. They are; pulmonary and systematic circulation, which transport blood throughout the body. Pulmonary circulation takes deoxygenated blood from the heart to lungs for oxygenation while the systematic circulation distributes this oxygenated blood throughout the body. Blood remains in a structure of veins and gets transported to all parts of the body at high pressure in a fast manner.

What are the Similarities Between Open Circulatory System and Closed Circulatory System?

• Both open circulatory system and closed circulatory system transport oxygen and nutrients to the organs and removes waste products.
• Also, they both have a heart and vessels.

What is the Difference Between Open Circulatory System and Closed Circulatory System?

Open circulatory system and closed circulatory system are two types of circulatory systems found in organisms. Open circulatory system can be seen in the two major phyla Arthropoda and Mollusca while the closed circulatory system can be seen in vertebrates and in few invertebrates. Moreover, a major difference between open circulatory system and closed circulatory system is that the purity of the blood. Organisms which posses an open circulatory system do not have true blood since the blood mixes with the interstitial fluid while the organisms which possess a closed circulatory system have pure blood that does not mix with any other fluids.

Another difference between open circulatory system and closed circulatory system is the pressure of the blood. Blood of the open circulatory system does not travel with pressure while the blood of the closed circulatory system travels with high pressure since the heart pumps blood through the vessels. The below infographic shows further information on the difference between open circulatory system and closed circulatory system.

Summary – Open Circulatory System vs Closed Circulatory System

In an open circulatory system, blood pressure remains low and body organs bath in the blood. In the closed circulatory system, pressure of the blood is high. The blood travel within a complex network of blood vessels, hence the organs do not contact with the blood. Furthermore, blood of the closed circulatory system never mixes with the interstitial fluid compared to the blood of open circulatory system. However, open circulatory system can supply blood with less energy requirement in contrast to the closed circulatory system which requires more energy to pump the blood. Thus, this is the difference between open circulatory system and closed circulatory system.

Reference:

1.Study.com, Study.com. Available here 
2.“The Circulatory System Review.” Khan Academy, Khan Academy. Available here 

Image Courtesy:

1.”Figure 40 01 01ab”By CNX OpenStax , (CC BY 4.0) via Commons Wikimedia  
2.”Circulatory System en”By LadyofHats, Mariana Ruiz Villarreal – Own work (Public Domain) via Commons Wikimedia