The circulatory system (a)(i) State the type of blood vessel that carries blood to the heart - Edexcel - GCSE Biology - Question 5 - 2012 - Paper 1

Blood is prevented from flowing backwards in the heart by the presence of valves. These valves ensure that blood flows in only one direction. For example, the atrioventricular valves between the atria and ventricles open to allow blood flow into the ventricles and close to prevent backflow when the ventricles contract.

The heart can be referred to as a ‘double-pump’ because it consists of two separate pumping systems. The right side of the heart pumps deoxygenated blood to the lungs for oxygenation, while the left side pumps oxygenated blood to the rest of the body. This dual-function allows for efficient circulation of blood within the body.