Renin is secreted by

Options

A. juxtaglomerular cells of juxtamedullary nephrons in response to high blood pressure
B. juxtaglomerular cells of juxtamedullary nephrons in response to low blood pressure
C. juxtaglomerular cells of cortical nephrons in response to high blood pressure
D. juxtaglomerular cells of cortical nephrons in response to increased osomolarity.

Answer

**Step-by-Step Solution:**

1. **Understanding Renin and Its Function**: Renin is an enzyme that plays a crucial role in regulating blood pressure and fluid balance. It is secreted in response to low blood pressure or low glomerular filtration rate (GFR).

2. **Identifying the Source of Renin**: Renin is secreted by specialized cells known as juxtaglomerular (JG) cells. These cells are located in the afferent arterioles of the kidney.

3. **Locating the Juxtaglomerular Apparatus**: The juxtaglomerular apparatus (JG apparatus) is a structure formed by the distal convoluted tubule (DCT) and the afferent arteriole. It is responsible for regulating blood pressure and GFR.

4. **Differentiating Nephron Types**: There are two types of nephrons in the kidney:
- **Cortical Nephrons**: These have shorter loops of Henle and are primarily located in the renal cortex.
- **Juxtamedullary Nephrons**: These have longer loops of Henle that extend deeper into the medulla and are associated with the JG apparatus.

5. **Response to Blood Pressure Changes**: When blood pressure is low, the JG cells in the juxtaglomerular apparatus detect this change and secrete renin into the bloodstream. This initiates a cascade of events that ultimately helps to raise blood pressure.

6. **Conclusion**: Given the information, renin is secreted by the juxtaglomerular cells located in the juxtaglomerular apparatus of the kidney, specifically in response to low blood pressure.

**Final Answer**: Renin is secreted by the juxtaglomerular cells of the juxtaglomerular apparatus.

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