Question

The epithelial layer of the upper respiratory tract is mostly comprised of pseudostratified ciliated columnar cells. Whereas, in the alveoli, the tiny sacs where gas change occurs, the epithelium is comprised of single squamos cells.

- Explain the functional significance of this difference in the tissues? Why don't the alveoli have the same kind of epithelium as the rest of the respiratory tract?

Answer 1

Pseudostratified columnar epithelia are tissues formed by a single layer of cells that give the appearance of being made from multiple layers. The nuclei of these epithelial cells are at different levels leading to the illusion of being stratified.

The presence of pseudostratified columnar epithelium in the upper respiratory tract (composed of the nose, trachea and bronchi) protects the lungs from these irritants. Goblet cells of the epithelium secrete mucus to trap particles and prevent them from traveling further down respiratory passages.

Alveoli are sites for gas exchange In the lungs and made up of simple squamous epithelium, which allows easy diffusion of gases from capillaries to Alveoli, hence it is made up of simple squamous epithelium.