Question: how small is a blood vessel

Rachel Dakin answered on 11 Nov 2013:

Good question Jem1 – they can get pretty small. There are different types of blood vessels; arteries, veins and capillaries.
Arteries carry oxygenated blood round the body and have quite large diameters. The largest is the aorta and in an adult that’s about the width of a garden hose! the further away from the heart the arteries are the thinner they become. Capillaries are the smallest blood vessels, they extend deep into different organs and tissues. Their walls are only 1 cell thick and this means oxygen and nutrients can get out of the blood and into the surrounding cells. Capillaries can be very thin – just the width of one red blood cell about 1micrometre (that’s what you get if you divide 1mm into a 1000!).
Veins carry the deoxygenated blood back to the heart and lungs and like arteries are different widths. A big difference between arteries and veins is the thickness of the walls. The blood in veins isn’t under pressure so they have thin walls.
Did you know if you took all the blood vessels out of an adult and laid them end to end they would stretch more than twice around the world!

I hope this answered your question