The Juxtaglomerular Apparatus and Renin

Key points

• • The juxtaglomerular apparatus is a specialised structure where the tubule of a nephron comes back to touch its own glomerulus.
• • It has three parts: the juxtaglomerular cells in the wall of the arteriole, the macula densa cells of the tubule, and supporting cells between them.
• • The juxtaglomerular cells sense a fall in blood pressure and release the enzyme renin into the blood.
• • The macula densa senses the salt in the tubular fluid and adjusts both renin release and the calibre of the glomerular arteriole.
• • Renin begins the renin-angiotensin-aldosterone system, which raises blood pressure by narrowing vessels and retaining salt and water.