A specific chamber? It's valves and each one has a different name. I'll list the chamber and the valve which stops 'backflow':-
Right Atrium: Tricuspid valve
Right Ventricle: Pulmonary valve
Left Atrium: Mitral valve
Left Ventricle: Aortic valve
The valves basically open when the relevant chamber is pumped but when pressure goes back towards the chamber they snap shut, stopping blood from going back through the heart/circulatory system.
A clot
Your heart keeps your blood "flowing"
The heart is the organ that keeps the blood flowing. Valves in the heart ensure the flow is only in one direction.
Heart blood vessels is what collects blood and pumps it to the lower chamber. This is what keeps the heart in working function.
Valves
The heart valves keep blood from flowing backward. This increases the efficiency of the pumping of the heart.
Arteries have no valves to prevent the blood from flowing backwards, but it is unnecessary when the heart keeps pumping. The blood pressure is highest when the blood is leaving the heart chamber into arteries -- the heart pumping keeps blood going one-way in the arteries.
diastole
The heart acts as a pump. When the heart beats, it pumps the blood in one direction.
The bicuspid valve allows blood to pass from the heart to the aorta but then keeps it from flowing back into the heart.
I think that its important to exercise for your heart because it keeps the blood flowing throughout your body.
gravity for those above your heart and valves for those below