Why is the normal blood pressure of a 3 year old different from the blood pressure of an adult?

Answer 1

You need to know the function of blood pressure:

First is to move blood through the circulatory system against the resistance of the blood vessels (mostly the capillaries, dbl for portal systems) and that means your mean bp must be at least 60 mm Hg (say 75/50). this is your's when you're asleep, when you're a small child, etc.

Second is the need to pump the blood uphill against gravity. Because of our tree dwelling ancestry we are a fully acrobatic species, that is, we can get blood to our feet if we stand on our head = for a 6 foot man that requires a bp of about 120/80.

Since a child is shorter, he needs less (but never less than the flow requirement).

Answer 2

Children typically have lower blood pressures than adults do, but a higher heart rate.

Answer 3

80/60