Journeys: Blood vessels. Stop 3

Three roads

Growney is building roads for blood from the heart to a muscle and back. Put each pipe on its own road!

An artery! Its thick springy wall can take the heart's pushes.

A capillary, thinner than a hair! Its wall is one cell thin, and oxygen goes right through it.

A vein! The wall is thin, and doors inside stop the blood flowing back.

Blood leaves the heart in pushes. This road needs a pipe with a thick springy wall!

In the muscle, oxygen has to get through the wall. This road needs the thinnest pipe!

Blood goes back to the heart gently. This road needs a wide pipe with doors!

The blood is going round! There are more capillaries than any other vessel. All the vessels together would wrap round the Earth two and a half times.