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)_____.