Final answer:
Fish gills were studied by August Krogh for insights into epithelial transport owing to their efficient gas exchange system and structural characteristics favorable for diffusion. The single layer of flat epithelial cells in gills, compared to cuboidal cells, makes them ideal for studying diffusion processes and active transport mechanisms.
Step-by-step explanation:
August Krogh utilized fish gills to study the fundamental mechanisms for epithelial transport because of the unique and efficient gas exchange system they possess. The fish gills operate on a countercurrent exchange mechanism, where water containing a high concentration of oxygen flows in the opposite direction to blood with a low concentration of oxygen within the gills. This setup maximizes the diffusion gradient, enhancing gas exchange efficiency and allowing more oxygen to be absorbed by the blood from the water.
The structure of gills further facilitates this process because of the large surface area provided by the thin, folded tissues. The choice to study gills for understanding epithelial transport is also reinforced by the fact that gills consist of a single layer of flat epithelial cells. These cells are more efficient in diffusion than cuboidal cells since their flatter shape increases the area for gas exchange and allows gasses and nutrients to travel shorter distances through the cells, making the diffusion process quicker and more efficient.
Therefore, the structure and function of fish gills offer a clear model for scientists like August Krogh to explore and understand how active transport and diffusion occur across epithelial barriers.