In birds, the main arteries taking blood away from the heart originate from the right aortic arch (or pharyngeal arch), unlike in the mammals where the left aortic arch forms this part of the aorta. The postcava receives blood from the limbs via the renal portal system. Unlike in mammals, the circulating red blood cells in birds retain their nucleus.
In birds the main arteries taking blood away from the heart originate from the right aortic arch (or pharyngeal arch) unlike in the mammals where the left aortic arch forms this part of the aorta The postcava receives blood from the limbs via the renal portal system Unlike in mammals the circulating red blood cells in birds retain their nucleus