Cells Composing the JG Apparatus

Juxta-Glomerular (JG) apparatus of the kidney is made up of which of the following cells-

Correct Answer: All the above

The Juxtaglomerular (JG) apparatus is formed at the junction of the DCT and glomerular afferent arteriole. It consists of three specialized cell types.

Three Components of JG Apparatus

• 1. Juxtaglomerular (JG) cells / Granular cells: Modified smooth muscle cells of the afferent arteriole wall. They secrete renin hormone and act as baroreceptors (sense decreased blood pressure).
• 2. Macula densa cells: Specialized epithelial cells of the DCT (Distal Convoluted Tubule). They detect Na⁺ concentration in tubular fluid — low Na⁺ → signals JG cells to release more renin.
• 3. Extraglomerular mesangial cells (Lacis cells): Located between macula densa and the glomerular tuft; act as communication cells between macula densa and JG cells.

RAAS Pathway

• JG cells release Renin → converts Angiotensinogen → Angiotensin I
• ACE (angiotensin-converting enzyme, mainly in lungs) → Angiotensin I → Angiotensin II
• Angiotensin II → stimulates aldosterone (adrenal cortex) → Na⁺ reabsorption → ↑ blood pressure