Water.
drink thin liquids
viscosity
The difference in thickness is representative of how far the blood has to travel. The right ventricle, which only has to pump blood to the lungs, will not need to be as muscular as the left ventricle which pumps blood to all the rest of the body.
compare the kinds of blood vessels according to the thickness of the walls
Capillary
It goes thicker to test this you can get blood and just leave it there, it will turn into a solid.
The smallest blood vessels are the capillaries.
Blood must be liquid and with a certain viscosity (thinness to thickness) for it to successfully pass through blood vessels and the heart without clotting.
capillaries
What is meant by blood thickness? Do you mean blood clotting faster or slower as in necessary to prevent strokes and heart attacks? People take medicine to "thin" the blood which really only means that the blood does not form clots as easily. Or as in too much blood? The amount of red cells compared to just the liquid part of blood changes due to many different conditions. People with "thick" blood may have too much iron, may have emphasema, may have had their spleen removed, may be dehydrated. Does this help?
Capillaries are the smallest blood vessels in the body (in terms of diameter), measuring about 20 micrometres (or one cell) across.