Oxygen rich blood leaves the lungs. It travels via the pulmonary vein to the heart. It travels through the aorta to the iliac artery. It then travels through the femoral artery to lower leg capillaries. It leaves the lower leg capillaries through the femoral vein It travels through the iliac vein to the inferior vena cava to the heart Carbon di oxide rich blood reaches the lungs through the pulmonary artery. Solution Oxygen rich blood leaves the lungs. It travels via the pulmonary vein to the heart. It travels through the aorta to the iliac artery. It then travels through the femoral artery to lower leg capillaries. It leaves the lower leg capillaries through the femoral vein It travels through the iliac vein to the inferior vena cava to the heart Carbon di oxide rich blood reaches the lungs through the pulmonary artery..