Structure through which oxygen must diffuse in passing from alveolar lumen to hemoglobin

Options

A. Surfactant containing liquid
B. Alveolarmembrane, basement membrane
C. Capillary endothelium, plasma and RBC membrane
D. All of the above

Answer

To answer the question regarding the structure through which oxygen must diffuse in passing from the alveolar lumen to hemoglobin, we can break down the process into several key steps:

### Step-by-Step Solution:

1. **Understanding the Alveolar Lumen**: The alveolar lumen is the air-filled space within the alveoli, where gas exchange occurs. Oxygen from the inhaled air enters this space.

2. **Diffusion Across the Alveolar Membrane**: The first structure that oxygen encounters is the alveolar membrane. This thin membrane allows for the diffusion of oxygen from the alveolar space into the bloodstream.

3. **Respiratory Membrane**: Next, oxygen must pass through the respiratory membrane, which consists of the alveolar epithelium and the capillary endothelium. This membrane is crucial for gas exchange as it is very thin, facilitating the diffusion of gases.

4. **Capillary Endothelium**: After passing through the respiratory membrane, oxygen diffuses across the capillary endothelium, which is the inner lining of the capillaries that transport blood.

5. **Plasma**: Once in the capillary, oxygen dissolves in the plasma, the liquid component of blood, allowing it to be transported to red blood cells.

6. **Red Blood Cells and Hemoglobin**: Finally, oxygen binds to hemoglobin within the red blood cells. Hemoglobin is a protein that carries oxygen throughout the body, delivering it to tissues that require it.

### Conclusion:
In summary, the structures involved in the diffusion of oxygen from the alveolar lumen to hemoglobin include the alveolar membrane, respiratory membrane, capillary endothelium, plasma, and red blood cells. Therefore, the correct answer to the question is that all of these structures are involved in the process.