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Juxta glomerular apparatus (JGA)

JUXTA GLOMERULAR APPARATUS (JGA)
•Defination
It is a specialised organ situated near the glomerulus of each nephron.
• Structure of JGA
It is formed by three structures-
1. Macula densa
2. Juxta glomerular cells
3. Extra glomerular mesangial cells

1. Macula densa-
- it is situated between afferent and efferent arterioles of the nephron.
- it is very close to afferent arteriole.
- it is formed by cuboidal epithelial cells.
2. Juxta glomerular cells-
- also called granular cells 
Because they contain secretary granules in their cytoplasm.
- JG cells are smooth muscle cells.
- JG cells situated in the wall of afferent arteriole just before it enters the bowman capsule.
- JG cells are mostly present in tunica media and tunica adventitia of the wall of afferent arteriole.
# Polar cushion / polkissen
It is a thick cuff that is formed by JG cells around the afferent arteriole before it enters the bowman capsule.
3. Extra glomerular mesangial cells-
Also called- 
°lacis cell, 
°agranular cell, 
°goormaghtigh cells
These cells are situated in the triangular region bound by the afferent arteriole, efferent arterioles and macula densa.

@Glomerular mesangial cells-
  -Also called intra glomerular mesangial cells
  - situated in between glomerular capillaries.
  - play an important role in regulating the glomerular filtration by their contractile property.
Function of JGA-
- JGA regulates the glomerular filtration rate and glomerular blood flow.
- It secrete the hormones like as renin, prostaglandin.
- Macula densa secretes thromboxaneA2.
- Extra glomerular mesangial cells secrete cytokines like interleukin-2 and TNF( tumor necrosis factor).

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