JGA

The JGA (juxtaglomerular apparatus) is located in the Glomerus inbetween the Afferent arteriole, Efferent arteriole, and the limb of the ascending limb of Loop of Henle. Here is where we will find three different types of cells each having an important role.

First we have Granular cells which are located in the arteriole walls of the Afferent arteriole. Also called (JG cells) Granular cells are enlarged, smooth muscle cells that mainly monitor the pressure of the afferent arteriole. Some of it's other lighter less important duties include stimulating Beta 1 and decreasing NaCl absorption in the Macula Densa.

Next there are Macula Densa cells which are located on the ascending limb of Loop of Henle. These are columnar epithelium cells that are tightly packed together. Macula Densa cells along with the Granular cells play an important role in monitoring the systemic blood pressure. While monitoring pressure is it's main role they also can detects high amounts of Na and Cl. If high amounts are noticed by the Macula Densa cells, they will decrease the amount of renin released to lower the Na and Cl levels.

The third type of cell located in the JGA are known as Extraglomerular Mesangial cells. These are located in the Glomerulus and act as the bonds between the Glomerular capillaries. These cells contain both actin and myosin, which allows them to be able to contract when stimulated by a nerve. The roles of Extraglomerular Mesangial cells is still somewhat mysterious, but some believe that these cells are conducive cells for letting the Macula Densa and the Afferent Arteriole communicate.