Juxtaglomerular Apparatus and Renal Blood Supply

Where the very start of the DCT of a nephron loops back and touches the afferent arteriole of that same nephron, two specialised cell populations meet to form the juxtaglomerular apparatus (JGA). On the arteriole side, certain smooth-muscle cells in the afferent arteriole wall are modified so that their cytoplasm becomes granular; these are the juxtaglomerular (JG) cells. On the tubule side, the cells of the DCT wall in this exact region are packed unusually densely, forming a patch called the macula densa. Together, the macula densa and the JG cells constitute the JGA, whose central role is regulating blood pressure within the kidney (largely through the renin-angiotensin-aldosterone pathway described later in this chapter). …