Why would you blood boil in the mesosphere?

Because the mesosphere is extremely thin and the temperatures in the mesosphere decrease rapidly with altitude.The blood would boil because of the low pressure. That's why when meteors hit earth they are burned in the mesosphere because the air is so thin there is enough gas molecules to cause it to burn.

That's why when Astronauts are about to go up in space they wear protective clothing/suits 

Hope this helped
have a great day

Igot the answer, here you go dude. 

Their worse are not meaningful;