Question

How can you turn a simple columnar epithelium into a water barrier?

Answer 1

The simple columnar epithelium are simply a single layer of long epithelial cells mainly seen in the regions where there is absorption and secretion .it can be ciliated and non-ciliated and is specifically structured to act as a barrier to the non specific movement of certain substances.

This question focuses on the absorption function of the simple columnar epithelium.The simple columnar epithelium can be converted to a water barrier with the help of the lateral specializations between the cells of this epithelium known as intercellular junction/cleft (IC).The tightness and the barrier properties are determined by the junctional complex which is inclusive of tight junctions (zonula occludens),adherent junctions (Zonula Adherens) and also desmosomes (macula adherens). Especially in kidneys and intestinal epithelium the cadherins (found in adherent junctions) span across the membrane for regulation of width of IC thereby influencing water balance .Also the tight junctions which are joined by transmebrane protien complexes also act as a obstucle for the movement of water.

The volume of the IC therefore determins the water absorption or serve as a water barrier thereby determining the osmotic gradient. Therefore in this way the simple columnar epithelium can be turned in to a water barrier with the help of tight junctions web(zona occludens ) or cadherins.