b. macula densa a group of cells derived from epi. of distal tubule cell becomes taller. narrow. with round N apical part arranged cells have processes connecting with other cells --function chemoreceptors - feel the nat ions concentrationb. macula densa ---a group of cells derived from epi. of distal tubule ---cell becomes taller, narrow, with round N apical part arranged ---cells have processes connecting with other cells ---function: chemoreceptors- feel the Na+ ions concentration