This article expresses the fact that the juxtaglomerular granular (JG) cells are present in the afferent arteriole, the efferent arteriole and the extraglomerular mesangium. However, they are much more numerous in the afferent arteriole.
The JG granular cells can be considered as "myoendocrine" cells, since they contain myofibrils and attachment bodies (like smooth muscle), as well as secretory granules and crystalline protogranules (like secretory endocrine cells). The picture at the top of this post is a good one to illustrate this.
Credits
Renal Corpuscle Image. 2019. Downloaded under a Creative Commons Attribution-Share Alike 4.0 International License from Wikimedia Commons. Author: Shypoetess. No changes were made.
Posts in this series
The Macula Densa Cells May Sense Tubular Salt Content Using a NHE2 Exchanger
The Macula Densa Cells Also Can Sense Sodium and Chloride Concentrations Using the NKCC2 Transporter
MAP Kinases are Activated by Low Tubular NaCl and Stimulate COX-2 Expression
Inhibition of nNOS in the Macula Densa leads to an Exaggerated TGF Response