¶ … physical properties diffusion structure function epithelia epithelial cells digestive circulatory systems animals larger end larger. In answer, surface area volume ratios (SA/V) ratios change organisms larger effect (s) change imposes structure function organisms. Epithelia: Solving the SA/V (surface-to-area volume) problem

"Epithelium is one of the four primary tissues of the body. It consists of cells usually arranged in sheets or tubules that are attached to the underlying basement membrane" (Epithelia, 2012, SUNY). One of the problems for the epithelium is that as a cell grows larger, the cell's volume increases at an exponentially faster rate than the cell's overall surface...

This could place a limit on the cell's size, since it limits the speed substances coming into the cell can diffuse throughout the entity (Moffatt 1998). However, a number of mechanisms have evolved to cope with the SA/V (surface-to-area volume) problem besides simply 'staying small.'
One solution is the cell changing its shape, either elongating or folding, given that an oval has a larger SA/V ratio than a circle and a folded cell membrane has a larger surface area as well (Moffatt 1998). Another solution is decreasing in overall volume since a "cell with a large water-filled vacuole in the center has much less active cytoplasm than its measurements would suggest. Its metabolic demands are…