___(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)_____.
Arteries and veins :
Final answer: Arteries carry oxygen-rich blood from the heart to all parts of the body and veins carry carbon dioxide-rich blood from all parts of the body back to the heart. Veins have thin walls and arteries have thick elastic walls. Blood flows at high pressure in arteries Valves are present in veins which allow blood to flow only towards the heart. Arteries divide into smaller vessels. These vessels further divide into extremely thin tubes called capillaries. The capillaries join up to form venules.