Difference Between Open Circulatory System and Closed Circulatory System

Open Circulatory System vs Closed Circulatory System

Open circulatory system and closed circulatory system are two ways in which the circulatory system functions in human and animal body. For normal body functions, and to distribute nutrients and other materials throughout 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 are required to pump blood through the organism and to remove waste. There are glaring differences between the two systems which are enumerated below.

Closed Circulatory System

In a closed system, blood remains in a network of vessels and does not leave it, while in an open system; blood is pumped into the system, pools around organs and tissues and then is retrieved back into circulation. Thus in an open circulatory system, all organs get bathed by blood whereas it does not happen in a closed circulatory system. With no veins to carry blood, animals with an open system are not subject to high blood pressure and have more blood than animals who have a close circulatory system.

It involves two major functions, pulmonary and systematic circulation. Pulmonary circulation takes deoxygenated blood through lungs to give it oxygen. Then, 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.

Open Circulatory System

Open circulatory system is simpler than closed system. Here heart pumps blood into open cavities from where 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.

Difference between Open and Closed Circulatory Systems

Open system requires less energy for distributing blood. For animals with a small body and slow metabolism, it is a better circulatory system. With blood pressure remaining low, and oxygen taking more time to reach cells, this is better as less active animals with low metabolism do not require high amounts of oxygen.

The closed system on the other hand carries blood at a higher pressure and delivers blood quickly which is suitable for animals with a fast metabolism. It also makes use of leaser blood. The animal is able to move, digest and eliminate waste easily and quickly.


• Circulatory system is a basic requirement of all organisms for regular supply of oxygen and nutrients throughout body cells.

• As we go up the animal chain from basic to more complex organisms, we see use of special tools which animals use to make closed circulatory system more efficient.

• In open system, blood pressure remains low and body organs are bathed with blood

• In closed system, blood pressure is high and is distributed quickly to help for fast metabolism.