Which one of the following acts as a physiological barrier to the entry of microorganims in human body?

Options

A. Epithelium of Urogenital tract
B. Tears
C. Monocytes
D. Skin

Explanation

To determine which option acts as a physiological barrier to the entry of microorganisms in the human body, we can analyze each option provided:

1. **Understanding the options**:
- **Option A: Epithelium of urinary genital tract** - While the epithelium does provide a physical barrier, it is not primarily a physiological barrier.
- **Option B: Tears** - Tears contain lysozyme, an enzyme that can break down the cell walls of certain bacteria, thus acting as a physiological barrier.
- **Option C: Monocytes** - These are white blood cells that help in the immune response by engulfing pathogens, but they do not act as a barrier to entry.
- **Option D: Skin** - The skin acts as a physical barrier, but it is not classified as a physiological barrier in the same way as tears.

2. **Identifying the physiological barrier**:
- Physiological barriers are those that actively work to prevent the entry of pathogens through biochemical means.
- Among the options, tears are known to contain lysozyme, which actively inhibits the growth of bacteria by breaking down their cell walls.

3. **Conclusion**:
- Based on the analysis, the correct answer is **Option B: Tears**, as they contain lysozyme which serves as a physiological barrier to the entry of microorganisms.

### Step-by-Step Solution:
1. Analyze each option provided in the question.
2. Identify which options act as barriers to microorganisms.
3. Focus on the definition of physiological barriers and their functions.
4. Conclude that tears, due to the presence of lysozyme, are the correct answer.