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

Options

A. Transitional epithelium of alveoli + squamous
epithelium of blood vessel
B. Swuamous epithelium of alveoli + endothelium
of blood vessel
C. Squamous epithelium of alveoli + cubical
epithelium of blood vessel
D. Cubical epithlium of alveoli + columnar
epithelium of blood vessel

Answer

To answer the question "In lungs, the air is separated from the venous blood through," we need to understand the structure of the lungs and the specific layers involved in gas exchange.

### Step-by-Step Solution:

1. **Identify the Structures Involved**:
- The primary structures involved in the separation of air from venous blood in the lungs are the **alveoli** (air sacs) and the **blood capillaries**.

2. **Understand the Layers**:
- The walls of the **alveoli** are made up of **squamous epithelium**, which is a thin layer of flat cells that facilitates gas exchange.
- The walls of the **blood capillaries** are lined with **endothelium**, which is also a thin layer of cells that allows for the efficient transfer of gases between the blood and the air in the alveoli.

3. **Recognize the Interstitial Space**:
- Between the alveolar epithelium and the capillary endothelium, there is a very thin **interstitial space**. This space is crucial for the diffusion of gases (oxygen and carbon dioxide) between the air in the alveoli and the blood in the capillaries.

4. **Evaluate the Options**:
- The question provides multiple-choice options. We need to identify which option correctly describes the layers that separate air from venous blood.
- The correct option must include the **squamous epithelium of the alveoli** and the **endothelium of the blood vessels**.

5. **Select the Correct Answer**:
- After evaluating the options, the correct answer is **squamous epithelium of alveoli and endothelium of blood vessels**. This option accurately reflects the two layers that separate the air in the alveoli from the venous blood in the capillaries.

### Final Answer:
The air in the lungs is separated from the venous blood through the **squamous epithelium of alveoli and endothelium of blood vessels**.

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