In lungs, the air is separated from the venous blood through

Options

A. Squamous epithelium `+` tunica external of bllod vessel
B. Squamouns epithelium `+` endotherlium of blood vessel
C. Transitional epithelium `+` tunica media of blood vessel
D. Columnar epithelium `+` 3 layered wall of bood vessel.

Answer

To answer the question "In lungs, the air is separated from the venous blood through," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure Involved**: In the lungs, the primary structures involved in gas exchange are the alveoli. The alveoli are tiny air sacs where oxygen and carbon dioxide are exchanged.

2. **Understand the Layers of the Alveoli**: The walls of the alveoli are made up of a thin layer of squamous epithelium. This type of epithelium is crucial because its thinness allows for efficient gas exchange.

3. **Consider the Blood Vessels**: Surrounding the alveoli are capillaries, which are small blood vessels. The walls of these capillaries are lined with endothelium, another type of thin epithelium.

4. **Gas Exchange Mechanism**: The exchange of gases (oxygen and carbon dioxide) occurs through simple diffusion. This process relies on the concentration gradient and the pressure gradient between the air in the alveoli and the blood in the capillaries.

5. **Identify the Correct Answer**: The air in the alveoli is separated from the venous blood in the capillaries by two main layers: the squamous epithelium of the alveoli and the endothelium of the capillaries. Therefore, the correct answer is that air is separated from venous blood through the squamous epithelium and the endothelium of the blood vessels.

### Final Answer:
In lungs, the air is separated from the venous blood through the squamous epithelium of the alveoli and the endothelium of the capillaries.

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