Home » Physiology

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.

Tags: juxtaglomerular apparatus, RAAS, tubuloglomerular feedback

Last updated: August 12, 2011

Share/Bookmark this!

One Comment

Leave a reply

Add your comment below, or trackback from your own site. You can also subscribe to these comments via RSS.

Be nice. Keep it clean. Stay on topic. No spam.

You can use these tags:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>


Who wrote this article?

This entry was posted by on August 12, 2011 at 9:08 pm and filed under Physiology category.

Subscribe Via Email

Enter Your Email To Subscribe

Blog Authors

BMI Calculator

Calculate calories burnt »

Relevant links

RSS Recent Questions in Medchrome

Recent Comments

RSS Recent Videos in Medchrome

Medchrome Networks

Established in 2009, The Network includes
Pedchrome- Pediatric Health Magazine
Epomedicine- E- Portal of Medicine
Medical tube - Video tube
Answers - Ask medchrome

Ask Medical Questions