Tubular cells secrete _____ and _____

Answer

To answer the question "Tubular cells secrete _____ and _____," we can break down the process of urine formation, particularly focusing on the tubular secretion phase.

### Step-by-Step Solution:

1. **Understanding Tubular Secretion**:
- Tubular secretion is one of the three main processes involved in urine formation, alongside glomerular filtration and tubular reabsorption. It occurs primarily in the renal tubules of the nephron.

2. **Identifying the Components Secreted**:
- During tubular secretion, certain substances are actively transported from the blood into the tubular fluid (filtrate). This process is crucial for the elimination of waste products and maintaining the body's acid-base balance.

3. **Key Substances Secreted**:
- The primary substances secreted by the tubular cells include:
- **Hydrogen ions (H+)**: These are secreted to help regulate the pH of the blood and maintain acid-base balance.
- **Potassium ions (K+)**: These are secreted to regulate potassium levels in the body, which is essential for normal cellular function.

4. **Final Answer**:
- Therefore, the correct answer to the question is: Tubular cells secrete **H+** and **K+**.