Question

The cavities of alveoli of lungs are lined by

• A. cuboidal epithelium
• B. columnar epithelium
• C. stratified cuboidal epithelium
• D. squamous epithelium

Answer 1

Answer: (D)

There are $300$ millions of alveoli (also called acini) in two lungs. The alveoli have very thin wall consisting of squamous epithelium. The wall of alveoli has an extensive network of blood capillaries interspersed with elastic and reticular connective tissue fibres. Due to very intimate contact of blood capillaries with the alveoli, the exchange of gases takes place easily.