Definition
- The juxtaglomerular apparatus (JGA) forms where the thick ascending limb of the loop of Henle contacts the afferent and efferent arterioles of the same nephron; components: macula densa, JG cells, lacis cells.
- Renin, an acid protease glycoprotein secreted by JG cells, converts angiotensinogen to angiotensin I, activating the renin-angiotensin system (RAS).
Structure of the Juxtaglomerular Apparatus
Components of the juxtaglomerular apparatus
Component
Macula densa
- Identity
- Modified epithelial cells of thick ascending limb of LOH
- Feature
- Densely packed; senses tubular fluid flow rate and ionic composition
JG cells
- Identity
- Modified epitheloid smooth muscle cells, mainly of afferent arteriole
- Feature
- Granular; secrete renin; also called Polkissen cells
Lacis cells
- Identity
- Extraglomerular mesangial cells between the arterioles and macula densa
- Feature
- Agranular; secrete renin and erythropoietin