The circulatory system consists of a closed network of blood vessels connected to the heart
Oxygenated blood is carried away from the heart and towards organs in arteries
These narrow to arterioles and then capillaries as they pass through the organ
In the organs, respiring cells use up the oxygen from the blood
The capillaries widen to venules and finally veins as they move away from the organs
Veins carry deoxygenated blood back towards the heart
lymphatic vessels
A different network of lymphatic vessels collect all the excess tissue fluid that leaks out of the capillaries and delivers it back to the circulatory system
