Why do the circulatory systems of land vertebrates have separate circuits to the lungs and to the rest of the body? view available hint(s) why do the circulatory systems of land vertebrates have separate circuits to the lungs and to the rest of the body? the large decrease in blood pressure as blood moves through the lungs may prevent efficient circulation through the rest of the body. land vertebrates are bigger and require more tubing to reach all areas of the body. the circuits increase the amount of surface area available for the diffusion of gases and nutrients in the body. blood is pumped to the lungs to be oxygenated before being pumped to the rest of the body.