Juxtaglomerular apparatus lies in relation to the following structure and have secretory function:

At the point where the afferent aeriole enters the glomerulus and the efferent aeriole leaves it, the tubule of the nephron touches the aerioles of the glomerulus from which it arose. At this location, which marks the sta of the distal convolution, there is a modified region of tubular epithelium called the macula densa. The macula densa is in close proximity to the JG cells. The lacis cells, the JG cells, and the macula densa constitute the juxtaglomerular apparatus.Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 38. Regulation of Extracellular Fluid Composition & Volume. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.