1. Blood in the gills runs in the opposite direction as the water outside the gill filaments. By running in the direction opposi
te the flow of water, the blood is always exposed to an area of water that has a higher level of oxygen. Oxygen moves across the membranes by diffusion. So if the gill had more oxygen than the water, the fish would lose oxygen to its surroundings. This is an example of:
Counter current system for oxygen exchange. This process allow the exchange through diffusion of oxygen from higher concentration of water to lower concentration in the fish blood, from the surface of the fish lammela,Therefore as blood flows through the gill capillaries,oxygen at higher diffusion gradient,enters the capillaries, sustained by higher diffsuion rate of Oxygen Counter by opposite blood flow.
