☆Alveoli:

》These are the structural and functional unit of lungs.

》These are vascularised membranous bag-like structure,which is the actual site of exchange of air between the atmosphere and lining of blood vessels.

》About millions of alveoli are present inside the lungs.

》Alveoli are thin walled structure lined by various cells which make the path easy for exchange.

》Lining of alveoli: -

• Simple squamous cells(Type-I pnuemocytes)= These are responsible for the exchange of gases, passing via the basement membrane and the endothelium of blood vessels.
• cuboidal cells(Type-II pnuemocytes) = They secrete surfactant(lecithin or any phospholiped) which make the walls smooth hence, increasing the rate of diffusion.

so the answer is:

Type I Squamous epithelium is involved in?

‐ exchange of air.

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