AEMCA Practice Exam

Which part of the kidney is responsible for sensing blood pressure changes and releasing renin?

1. Distal convoluted tubule

2. Juxtaglomerular apparatus

3. Proximal convoluted tubule

4. Glomerulus

The correct answer is: Juxtaglomerular apparatus

The juxtaglomerular apparatus plays a crucial role in regulating blood pressure within the kidneys. This specialized structure is located near the glomerulus, where the afferent arterioles and distal convoluted tubule come together. It consists of juxtaglomerular cells, macula densa cells, and mesangial cells. When blood pressure decreases, the juxtaglomerular cells sense this change due to the reduced stretch in the arterial walls. In response, they release the enzyme renin into the bloodstream. Renin plays a key role in the renin-angiotensin-aldosterone system (RAAS), which ultimately leads to increased blood pressure through various mechanisms such as vasoconstriction and sodium retention. This feedback mechanism is vital for maintaining blood pressure homeostasis and ensuring adequate renal perfusion. The other parts of the kidney do not have this specific function. The distal convoluted tubule is involved in electrolyte balance and fluid regulation, while the proximal convoluted tubule focuses on reabsorption of water, ions, and nutrients. The glomerulus primarily functions in filtering blood to form urine but does not actively sense blood pressure changes or release renin.