Which of the following substances are secreted by tubular cells into the filtrate during urine formation ?

Options

A. Glucose, amino acids , `Na ^+`
B. `H^+ , K^+` , aminoacids
C. `Na^+ , H^+` , aminoacids
D. `K^+ , H^+` ammonia

Answer

To solve the question regarding which substances are secreted by tubular cells into the filtrate during urine formation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Nephron Structure**:
- The nephron is the functional unit of the kidney, consisting of the glomerulus and the renal tubule (which includes the proximal tubule, loop of Henle, distal tubule, and collecting duct).

2. **Filtration Process**:
- The glomerulus is responsible for the filtration of blood, where water, ions, and small molecules are filtered into the Bowman’s capsule.

3. **Reabsorption and Secretion**:
- As the filtrate moves through the renal tubule, various substances are reabsorbed back into the blood and others are secreted into the filtrate.

4. **Proximal Tubule**:
- In the proximal convoluted tubule, about 70-80% of electrolytes are reabsorbed.
- Glucose and amino acids are primarily reabsorbed here, while hydrogen ions, potassium ions, and ammonia are secreted into the filtrate.

5. **Loop of Henle**:
- The descending limb is permeable to water but not to electrolytes, while the ascending limb is permeable to electrolytes but not to water. No significant secretion occurs here.

6. **Distal Convoluted Tubule**:
- In the distal convoluted tubule, sodium and bicarbonate ions are reabsorbed.
- Similar to the proximal tubule, hydrogen ions, potassium ions, and ammonia are secreted into the filtrate.

7. **Conclusion**:
- Based on the functions of the different parts of the nephron, the substances that are secreted by tubular cells into the filtrate during urine formation include hydrogen ions, potassium ions, and ammonia.
- Glucose and amino acids are reabsorbed, not secreted.

### Final Answer:
The correct option is **Potassium, Hydrogen, and Ammonia**.

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