Write a short note on Juxta Glomerular Apparatus.

1. Some smooth muscle cells of the wall of afferent arteriole are modified in such a way that their sarcoplasm is granular. These cells are called juxtaglomerular (JG) cells. 

2. In each nephron, initial part of DCT makes contact with the afferent arteriole of same nephron. 

3. Cells in the wall of DCT in this region are packed more densely than those in other region of DCT. This is called macula densa. 

4. Macula densa and the JG cells together form Juxta Glomerular Apparatus (JGA). 

5. The JGA plays an important role in blood pressure regulation within the kidney.