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LET'S EXPLORE The human body

What are blood vessels?

The network of arteries (red) and veins (blue)The network of arteries (red) and veins (blue)Blood travels along thousands of tubes, called blood vessels. Blood vessels that take blood away from the heart are called arteries. Blood vessels that take blood towards the heart are called veins. The arteries and veins in your body are like a road network. There are “motorways” (the main blood vessels) as well as “lanes” and “tracks”, tiny vessels called capillaries that reach all the cells in the body. Altogether, your blood vessels are about 100,000 kilometres (60,000 miles) long, or more than twice the distance around the world.

Veins

Valves inside veinsValves inside veinsVeins carry blood containing carbon dioxide and other wastes from the cells towards the heart. The larger veins have valves inside them. These are “doors” that open and close rather like canal locks. The valves ensure that blood cannot leak back.



Arteries (left) have thicker walls than veins (right)Arteries (left) have thicker walls than veins (right)

Arteries

Cherry-red blood containing oxygen and nutrients flows from the heart to the body's cells through your arteries. Arteries have much thicker walls than veins because they carry blood pumped under high pressure from the heart. 

You can feel the heart's pumping action by placing your fingers on the inside of the wrist, a point where a main artery lies close to the surface of your skin.

The only place you can normally see blood in your body is on the retina at the back of your eye. This is revealed when photo is taken of you by flashlight.

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