So let's take a look at the following diagram that basically describes several of these epithelial cells binding together to form the membrane the lining of our proximal convolute tubule. So we have these epithelial cells that are connected, and these are our tie junctions that prevent the movement of waste products from the lumen of the proximal convoluted tubule. This is where the filtrate is found to the interstituum of our renal cortex, to these peritubular capillaries that are found within our interstituum. Now, this side of the membrane that faces the lumen portion is known as the apical side, and this other side across it is known as the basil lateral side. So we have ions that enter via our apical side, eventually travel down through the basil lateral side, and will enter the peritubular capillaries. So now let's actually discuss how the absorption and secretion takes place across our cell membrane of the epithelial cells found within the proximal convoluted tubule.