Expert: Walter Hintz - 10/9/2010

Question
why the cells of big and small animals are histologically similar? what restricts the size of the cells that make up the tissue?

Answer
There is a math principle called the scale effect that states when you increase the size of cell you decrease the ratio of the surface area to the volume.
  Consider a cube with an edge in 1 inch
    The surface is 1 x x 1 x 6 or 6 square inches
    The surface area is 1 x 1 x1  or 1 cubic inch
       The ratio is 6-1
  Now we increase the cube to 2 inches on a side
    Surface area is 2 x 2=4 x 6 or 25  Square inches
      The volume is 2 x 2 x 2       8  Cubic inches
             ratio is 3-1
What does this have to do with cell size? Nutrients and gas exchanges must pass through the surface area of the cell. If the cell doubles in size the need of the cell double but the surface area is not enough to carry out the exchanges is. What does the cell do? It divides
Therefore the cells of all living animals must remain small no matter how big an animal is