The main difference between the pulmonary and systemic circulation is in where the blood goes.
In pulmonary circulation, blood is carried to and from the lungs, where it comes in contact with the oxygen-exchange surfaces of the lungs. On the other hand in systemic circulation blood runs to and from the cells in the rest of the body.
Another difference is that in regard to the pulmonary circulation, blood that has completed the pulmonary circuit is rich in oxygen while in systemic circulation, blood that has completed the systemic circuit has been depleted of oxygen
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