The larger the animal (or human) the greater the supply of blood, this
enables all portions of the body to be nourished. The size of a animal's
heart is in proportion to the volume of blood it has to pump, except for
birds, where the heart is proportionally larger because of the increased
work it must do. Therefore,if a species has any organ which is larger in
proportion to it's size than other equally sized species, it is because
that organ has increased capacity to do it's job.The role of blood
pressure regulation is to deliver nourishment and take away toxins, if
pressure were lower in larger animals, their brains would starve,if it
were higher in smaller animals, they would stroke out.
