types of blood

1. the artery 

the elastic fibres allow the artery to stretch under pressure
the thick muscle can contract to push the blood along

   2.  the vein
veins have valves which act to stop the blood from going in the wrong direction
thin muscle and elastic fibres

   3.  the capillary
they exchange materials between the blood and other body cells
the wall of a capillary is only one cell thick