What components make up the juxtaglomerular apparatus?

The juxtaglomerular apparatus is a specialized structure located near the glomerulus of the nephron and plays a crucial role in regulating blood pressure and the filtration rate of the kidney. The correct answer identifies its two primary components: juxtaglomerular cells and the macula densa.

Juxtaglomerular cells are modified smooth muscle cells found in the walls of the afferent arterioles and are responsible for the secretion of renin, an enzyme critical for the regulation of blood pressure. The macula densa, on the other hand, is a group of specialized epithelial cells located in the distal convoluted tubule that monitor sodium concentration in the filtrate. When sodium levels are low, the macula densa signals the juxtaglomerular cells to release renin, initiating a cascade that ultimately raises blood pressure.

This interplay between the juxtaglomerular cells and the macula densa helps maintain homeostasis through the regulation of glomerular filtration rate and systemic blood pressure. Understanding this relationship is essential for comprehending kidney function and the body’s fluid balance. The other choices do not accurately represent the components of the juxtaglomerular apparatus, focusing on different structures or functions unrelated to the