The respiratory system is the network of organs and tissues that help you breathe. It includes your airways, lungs, and blood vessels. The muscles that power your lungs are also part of the respiratory system. These parts work together to move oxygen throughout the body and clean out waste gases like carbon dioxide.

The lungs are covered by the serous membrane, the pleural membrane, which has the parietal and the visceral layers. The visceral pleura of the lung is lined by a mesothelial layer with underlying connective tissue and elastic fibers.

The trachea lining consists of a type of tissue called pseudostratified (ciliated) columnar epithelium. This single layer of ciliated cells appears stratified because the cells vary in thickness, and their nuclei are located at different levels.

The majority of the respiratory tree, from the nasal cavity to the bronchi, is lined by pseudostratified columnar ciliated epithelium. The bronchioles are lined by simple columnar to the cuboidal epithelium, and the alveoli possess a lining of thin squamous epithelium that allows for gas exchange.

References:

Respiratory System. (2020, January 24). Cleveland Clinic. Retrieved from https://my.clevelandclinic.org/health/articles/21205-respiratory-system

Khan, Y. S., & Lynch, D. T. (2021 May 10). Histology, Lung. National Library of Medicine. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK534789/

Nash, A. A., Dalziel, R. G., & Fitzgerald, J. R. (2015, February 6). Chapter 8 – Mechanisms of Cell and Tissue Damage. ScienceDirect. https://www.sciencedirect.com/topics/medicine-and-dentistry/ciliated-epithelium

Kia’i, N., & Bajaj, T. (2021 May 10). Histology, Respiratory Epithelium. National Library of Medicine. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK541061/