What is the primary function of the juxtaglomerular apparatus in renal physiology?

• A. To secrete waste products into the urine
• B. To reabsorb sodium and water from the filtrate
• C. To produce erythropoietin for red blood cell production
• D. To regulate blood pressure and the rate of glomerular filtration

Answer: (D)

Verified step by step guidance

1. Understand the anatomy of the juxtaglomerular apparatus (JGA), which is located near the glomerulus in the kidney and consists of the macula densa, juxtaglomerular cells, and extraglomerular mesangial cells.
2. Recognize that the JGA plays a crucial role in regulating blood pressure and glomerular filtration rate (GFR) through the renin-angiotensin-aldosterone system (RAAS).
3. Identify that the macula densa cells sense sodium chloride concentration in the distal convoluted tubule, which provides feedback on the rate of filtration.
4. Learn that juxtaglomerular cells release renin in response to low blood pressure or low sodium chloride levels, initiating the RAAS pathway to increase blood pressure and GFR.
5. Conclude that the primary function of the JGA is to regulate blood pressure and the rate of glomerular filtration, rather than secreting waste, reabsorbing sodium and water, or producing erythropoietin.