juxtaglomerular apparatus
Last reviewed 11/2023
The juxtaglomerular apparatus is a small endocrine organ associated with individual nephrons within the kidneys. It is composed of:
- the macula densa of the proximal distal tubule of the nephron
- the closely situated afferent arteriole of the same nephron
- 2 cell types intervening between macula densa and arteriole in the 'mesangial' region:
- granular mesangial cells containing prorenin granules, the precusor of renin; they are modified smooth muscle cells which secrete renin into the afferent arteriole
- agranular lacis cells
- sympathetic nerves lying in close proximity to the granular cells
The JGA is in an ideal position to monitor the amount and composition of urine in the nephron and blood in the afferent arteriole. Renin secretion may be modified accordingly.