Cells of macula densa produce

Options

A. Erythropoietin and relaxin
B. Renin
C. Angiotensionogen
D. Angiotensin.

Answer

**Step-by-Step Solution:**

1. **Understanding Macula Densa**: The macula densa is a group of specialized epithelial cells located in the distal convoluted tubule (DCT) of the nephron. These cells are positioned near the afferent and efferent arterioles of the glomerulus.

2. **Characteristics of Macula Densa Cells**: The cells of the macula densa are columnar in shape and are denser compared to surrounding cells. This density is due to their close proximity to the arterioles, which allows them to perform their function effectively.

3. **Function of Macula Densa**: The primary function of the macula densa cells is to act as chemoreceptors. They monitor the chemical composition of the filtrate (the fluid in the nephron) as it passes through the DCT.

4. **Signal to Juxtaglomerular Apparatus**: When the macula densa detects changes in the concentration of sodium chloride (NaCl) in the filtrate, it sends signals to the juxtaglomerular apparatus (JGA). The JGA is responsible for regulating blood pressure and fluid balance.

5. **Production of Renin**: In response to signals from the macula densa, the juxtaglomerular cells (part of the JGA) secrete renin, an enzyme that plays a crucial role in the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure.

6. **Conclusion**: Based on the function of the macula densa, the correct answer to the question is that the cells of the macula densa produce signals that stimulate the juxtaglomerular apparatus to secrete renin.

**Final Answer**: The cells of the macula densa produce signals that lead to the secretion of renin.

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