A cell that uses diffusion for primary material interchange is the Red
Blood Cell. Being small increases overall surface area and therefore,
more material can be diffused. Also, the cell is able to go into the
tiniest of capillaries and still function effectively. Homeostasis is
the body's ability to maintain a constant internal environment. By
having multiple cells, the various internal variables (blood sugar,
sodium level, urea concentration etc.) can by controlled by one type of
cell and therefore, because that type of cell only has to worry about 1
variable it can do its job effectively and efficiently