What are the two circuits of the cardiovascular system? what does it mean to say that the cardiovascular system is a closed system? what would happen if there was less blood pumped to the systemic circuit than the pulmonary circuit?

The two circuits of the cardiovascular system are: Pulmonary Circuit and Systematic Circuit. The pulmonary circuit is shorter than the systemic and is responsible for carrying deoxygenated blood to the lungs from the right atrium, for oxygenation. The systemic circuit is longer and leaves the aortic artery, carrying oxygenated blood throughout the body and nutrients for survival. If less blood were pumped into the systemic circuit, this amount would not be sufficient to compensate for the organism's needs, with the corresponding consequences that this would entail.  

It is said that the cardiovascular system is a closed system because blood travels inside a network of blood vessels without leaving them.

geographic isolation