Why are the desmosomes connecting the keratinocytes so important?

The epithelium of the respiratory tract is mostly of the pseudostratified columnar ciliated type, but in the alveoli, the tiny sacs where oxygen and carbon dioxide are exchanged between the blood and inhaled air, the epithelium is simple squamous. Explain the functional significance of this histological difference. That is, why do the alveoli not have the same kind of epithelium as the rest of the respiratory tract? Explain your answer in 4 to 5 sentences. Indicate the reference/s of your answer.

How do ceruminous glands release its secretion (merocrine, apocrine, holocrine)?

is non-keratinized stratified squamous epithelium watertight?