Schematic drawing of the architecture of a nephron, showing the position of the macula densa in the nephron and its relationship to the glomerulus of origin. A magnified view of the contact area of the macula densa with the glomerulus is shown on the right. MD, macula densa; AA, afferent arteriole; EA, efferent arteriole, GC: granular cell, SMC: smooth muscle cell.