In the cardiac cycle, blood flowing into the heart is called the systole.
There are valves in the heart - and the larger blood vessels that stop the blood flowing backwards.
The valve
The flow of blood from the heart to the lungs and back to the heart is called the pulmonary circulation.The blood flowing from the heart to the lungs would be deoxygenated and blood flowing towards the heart from the lungs would be oxygenated.
Valves prevent the backflow of blood, in this case the semilunar valves stop blood flowing back into the heart.
There are two ways that blood is kept flowing in the same direction. The heart is pumping it in that direction, and blood vessels contain valves which prevent blood from flowing in the wrong direction.
There are valves in the heart - and the larger blood vessels that stop the blood flowing backwards.
The valve
All the blood flowing through the intestines passes through the liver on its way back to the heart.
The valve
The flow of blood from the heart to the lungs and back to the heart is called the pulmonary circulation.The blood flowing from the heart to the lungs would be deoxygenated and blood flowing towards the heart from the lungs would be oxygenated.
Valves
Blood coming out of the capillaries passes into vessels of increasing diameter as it flows back toward the heart. It is usually deoxygenated.
valves keep blood from flowing back into the heart and help pump oxygen-poor blood back to the heart.
When the blood is flowing back to the heart, the blood has already given off its oxygen to the rest of the body which means it contain less oxygen concentration in the blood. and when blood is flowing from the heart to the rest of the body, the blood contains high level of oxygen because they were being given oxygen by the lungs which passes along the heart and the heart pumps it to the rest of the body.
Valves prevent the backflow of blood, in this case the semilunar valves stop blood flowing back into the heart.
Your heart keeps your blood "flowing"
2 of these valves (one on each side) stop blood from flowing back into the atria chambers of the heart when the heart is contracting and expelling blood. The other two are there to stop blood flowing out of the ventricles when the heart is filling up with blood. One stops blood flowing through the aorta to supply the body and the other stops it flowing through the pulmonary artery to the lungs.