At the same time, two potassium ions are pumped from the outside to the inside of the cell. And what this ultimately does is it establishes a gradient for sodium. So inside the cell, we have less sodium than on the outside. And so what happens on the apical side of our cell? The apical side is the side that points towards the lumen of the thick loop of Henley. The inside of the tubule, we have these passive co transport proteins that allow the movement of the ions down their electrochemical gradient.