It stimulates the granule cells to release Renan. And Renan is the proteolytic enzyme that is responsible for controlling the Rena angiotensin aldosterone pathway which regulates our blood pressure in the body. So these are the two functions of the macula densa cells. They essentially control the release of Renan and they also control the dilation of our a fairing arterial, thereby controlling the filtration rate within our glomerulus. Now, the other cells basically shown in brown are our epithelial cells and these are cuboidal epithelial cells. Now, the major difference between the epithelial cells in the distal convolute tubule and the epithelial cells in the proximal convolute is the following in the proximal convolute, our epithelial cells contain microvilli and this increases the reabsorption in the proximal convolute tubule.