So the Proximal convolute not only reabsorbs and secretes molecules and ions, but it also prevents the movement of waste products from actually returning and moving back into our blood plasma, such as, for example, urea. Now, if we zoom in on any section of the Proximal Convoluted tubule, if we examine the inner lining of that tubule, we're going to see epithelial cells. So the inner wall lining of the Proximal Convoluted tubule contains many of these epithelial cells that are connected by special types of junctions known as tide junctions. And what these tide junctions do is they basically prevent the movement of these waste products from the lumen of our Proximal Convoluted tubular from the filtrate back into our blood plasma of these peritubular capillaries. Now, all the surrounding tissues found around the Proximal Convoluted tubule is known as our interstituum. So what the Proximal Convolutes do is they prevent the movement of these waste products from the filtrate back into our interstituum.