That would be a capillary.
There is the arteries, veins and capillaries along with the blood cells etc
In your body or outside of your body(man made) I.v. Tube. In your lungs the bronchial veins /venules/tubes receive blood from aterioles or capillaries. This I think is where literally the trash from the blood(carbon dioxide is expelled and oxygen is taken into the blood).I think. biology.about.com