Which one of the following acts as a physiological barrier to the entry of microorganisms 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 need to analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Physiological Barriers**:
- Physiological barriers are mechanisms that prevent the entry of pathogens into the body. They include physical and chemical defenses.

2. **Evaluating the Options**:
- **Option A: Epithelium of Urogenital Tract**:
- The epithelium provides a physical barrier, but it is not primarily a physiological barrier. It does help in protecting against infections but is not classified under physiological barriers.

- **Option B: Tears**:
- Tears contain lysozymes, which are enzymes that break down the cell walls of bacteria. This makes tears a physiological barrier as they actively inhibit the growth of microorganisms.

- **Option C: Monocytes**:
- Monocytes are a type of white blood cell involved in the immune response. They are part of the adaptive immune system and do not act as a barrier to entry.

- **Option D: Skin**:
- Skin acts as a physical barrier to pathogens but is not classified as a physiological barrier in the same way that tears are, which have a biochemical action against microorganisms.

3. **Conclusion**:
- After evaluating all the options, the correct answer is **tears** (Option B) as they contain enzymes that actively prevent the entry of microorganisms.

### Final Answer:
The correct option is **tears**.

---