Question
Which of the following is the lining epithelium of the trachea?
| A. |
Simple squamous epithelium |
| B. |
Transitional epithelium |
| C. |
Stratified squamous epithelium |
| D. |
Pseudostratified ciliated columnar |
|
Correct Answer » D Explanation |
 |
The tracheal lining must facilitate both protection and mucociliary clearance.
– Pseudostratified ciliated columnar epithelium possesses cilia and goblet cells, aiding in trapping and removing inhaled debris via the mucociliary escalator.
Why Option A is Incorrect (Simple squamous epithelium):
– Found in sites of passive diffusion (alveoli, endothelium), not protective enough for exposed airways.
– Lacks cilia and goblet cells, so does not function in mucociliary clearance.
– Common in alveoli and blood vessels, not airways.
Why Option B is Incorrect (Transitional epithelium):
– Specializes in stretching, present in the urinary tract (ureters, bladder).
– Not ciliated; absent in respiratory tract lining.
– No tracheal sections have transitional epithelium.
Why Option C is Incorrect (Stratified squamous epithelium):
– Provides protection in areas of abrasion (oral cavity, esophagus); non-ciliated.
– In some upper respiratory regions (e.g., oropharynx), but not the trachea.
– Lacks goblet cells required for mucus production.
Why Option D is Correct (Pseudostratified ciliated columnar epithelium):
– Lines most of the conducting portion of the respiratory tract, including the trachea.
– Features cilia (for mucociliary clearance) and goblet cells (mucus secretion).
– Well adapted for defense against inhaled pathogens/particles.