April 23, 2024

Function of Juxtaglomerular Apparatus (JGA)

  • August 12, 2011
  • 2 min read
Function of Juxtaglomerular Apparatus (JGA)

Juxtaglomerular Apparatus or Complex is a specialized region of a nephron where the afferent arteriole and Distal Convoluted Tubule (DCT) come in direct contact with each other. Juxtaglomeruar Apparatus (JGA) consists of:

1) Juxtaglomerular cells (modified smooth muscle cells) of afferent arteriole including renin containing (synthesizes and stores renin) and sympathetically innervated granulated cells which function as mechanoreceptors to sense blood pressure.

2) Macula densa cells (Na+ sensors) of Distal Convoluted Tubule (DCT) which function as chemoreceptors to sense changes in the solute concentration and flow rate of filtrate.

3) Juxtaglomerular/Extraglomerular mesangial cells (Lacis cells) forming connections via actin and microtubules which allow for selective vasoconstriction/vasodilation of the renal afferent and efferent arterioles with mesangial cell contraction.

Functions of Juxtaglomerlar Apparatus (JGA):

  1. Local transmission of Tubuloglomerular Feedback (TGF) at its own nephron via angiotensin II (AT II)
  2. Systemic production of Angiotensin II (AT II) as part of Renin-Angiotensin-Aldosterone System (RAAS)

Tubuloglomerular Feedback (TGF) Mechanism

The tubuloglomerular feedback mechanism has 2 components that act together to control GFR:

  1. Afferent arteriolar feedback mechanism
  2. Efferent arteriolar feedback mechanism

Increased renal arterial pressure leads to an increased delivery of fluid (increased osmolality or increased flow rate) to the macula densa. The macula densa senses the load and causes constriction of nearby afferent arteriole, increasing the resistance. This will return osmolality and filtrate flow rate to normal.

Decreased renal arterial pressure leads to a decreased delivery of fluid (decreased osmolality or decreased flow rate) to the macula densa. The macula densa senses this and causes:

  1. Vasodilation of afferent arteriole
  2. Constriction of efferent arteriole as a result of renin release by stimulated JG cells

Renin Angiotensin Aldosterone System (RAAS)

When systemic blood pressure decreases, there is decreased stretch of JG cells, which leads to their release of renin. Renin release causes the activation of renin-angiotensin mechanism, which ultimately leads to an increased blood pressure.

About Author

Sulabh Shrestha

Intern doctor and Medical Blogger Sulabh Shrestha


  • With increased efferent arteriolar resistance there should be increased GFR and this increase will cause a negative feedback to decrease GFR which helps maintaining constant GFR

    Is this step missed in the flowchart?

    Same for the other side of decreased afférent resistance.

  • good one

  • very well done,

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