Final answer:
The macula densa is a cluster of cells in the distal convoluted tubule that communicates with juxtaglomerular cells to regulate kidney function and blood pressure.
Step-by-step explanation:
The macula densa is a group of modified epithelial cells in the distal convoluted tubule that touch the granular or juxtaglomerular cells. These cells form a critical part of the juxtaglomerular apparatus (JGA), which is essential for monitoring the composition of the fluid in the distal convoluted tubule (DCT) and for regulating the glomerular filtration rate (GFR) in response to changes in blood pressure, blood volume, or electrolyte balance.
The macula densa cells release paracrine signals such as ATP and adenosine in response to Na+ concentration and the flow rate of fluid, which communicate with juxtaglomerular cells of the afferent arteriole to influence blood flow and filtration in the kidneys. Collectively, the macula densa and the juxtaglomerular cells contribute to the regulation of blood pressure and kidney function.