白水房

The juxtaglomerular apparatus (JGA) is a structure in the kidney that consists of the macula densa, granular cells, and mesangial cells. The macula densa detects changes in sodium ion concentration in the tubular fluid and regulates the release of renin from the granular cells. The granular cells synthesize and secrete renin. The mesangial cells have supporting, contracting, and phagocytic functions. The afferent and efferent arterioles of the glomerulus are connected to the distal convoluted tubule outside the renal corpuscle. When the macula densa senses changes in sodium ion concentration in the afferent arteriole, it regulates the secretion of renin from the granular cells. Renin then regulates the contraction of the mesangial cells, thereby regulating the blood flow in the afferent arteriole (autoregulation).