Which of the following is not a character of
respiratory surface?

Options

A. Thin, permeable to gases
B. Extensive
C. Least vascular
D. Moist

Answer

To determine which of the following is not a character of a respiratory surface, we need to analyze each option provided:

1. **Thin and permeable to gases**:
- A respiratory surface must be thin to allow for efficient gas exchange. The alveoli in the lungs are thin-walled structures that facilitate the diffusion of oxygen and carbon dioxide. Therefore, this characteristic is true for respiratory surfaces.

2. **Extensive**:
- The respiratory surface should have a large surface area to enhance gas exchange. The lungs contain numerous alveoli, which increase the surface area available for diffusion. Thus, this characteristic is also true for respiratory surfaces.

3. **Least vascular**:
- This statement is incorrect. A respiratory surface must be highly vascularized to ensure that oxygen can be transported efficiently from the lungs to the bloodstream and that carbon dioxide can be removed. The presence of a rich network of blood vessels (capillaries) is essential for effective gas exchange. Therefore, this characteristic is not true for respiratory surfaces.

4. **Moist**:
- A moist surface is crucial for gas exchange as it allows gases to dissolve and diffuse more easily. The alveoli are lined with a thin layer of moisture, which aids in the diffusion process. Hence, this characteristic is true for respiratory surfaces.

**Conclusion**: The option that is not a character of a respiratory surface is **least vascular**.