What is the first layer of the diffusion membrane made of?

Step-by-step solution

The gradient is present for CO2 in the opposite direction, i.e., from tissues to blood and blood to alveoli. As the solubility of CO2 is 20-25 times higher than that of O2, the amount of CO2 that can diffuse through the diffusion membrane per unit difference in partial pressure is much higher compared to that of O2 . The diffusion membrane is made up of three major layers namely, the thin squamous epithelium of alveoli, the endothelium of alveolar capillaries and the basement substance (composed of a thin basement