The juxtaglomerular apparatus is form by cells near the glomerulus of the kidney, consisting of: juxtaglomerular cells (JG cells), epithelioid cells in the media of the afferent arterioles as they enter the glomerulus macula densa: tubular epithelium at the region of afferent arteriole and efferent arteriole to the glomerulus The JG cells secrete renin, a process mediated by angiotensin II and vasopressin.