Fill in the blanks of the following paragraph using just two words – arteries and veins.
(a) carry oxygen-rich blood from the heart to all parts of the body and (b) carry carbon dioxide-rich blood from all parts of the body back to the heart. (c) have thin walls and (d)_ have thick elastic walls. Blood flows at high pressure in (e). Valves are present in (f) which allow blood to flow only towards the heart. (g) divide into smaller vessels. These vessels further divide into extremely thin tubes called capillaries. The capillaries join up to form (h).
