Final answer:
The Juxtaglomerular Apparatus (JGA) is the specialized structure consisting of macula densa and juxtaglomerular cells near and within the distal tubule. It monitors blood pressure and stimulates the release of Renin & Erythropoietin. The macula densa monitors fluid composition and releases paracrine signals, while the juxtaglomerular cells secrete renin and erythropoietin.
Step-by-step explanation:
The specialized structure consisting of macula densa and juxtaglomerular cells near and within the distal tubule that monitors blood pressure and stimulates the release of Renin & Erythropoietin is the Juxtaglomerular Apparatus (JGA). The JGA is located just outside Bowman's capsule and the glomerulus.
The macula densa, a cluster of cuboidal epithelial cells in the JGA, monitors the fluid composition in the distal convoluted tubule. In response to changes in sodium concentration, the macula densa releases paracrine signals like ATP and adenosine.
The juxtaglomerular cells, which are modified smooth muscle cells in the afferent arteriole, contract or relax in response to these paracrine signals. These cells secrete renin, an enzyme involved in blood pressure regulation, and erythropoietin, a hormone that stimulates red blood cell production.