Question

Which one of the following epithelial cell types is primarily located in the tracheal mucosa of a healthy adult human?

• A. Transitional
• B. Keratinized stratified squamous
• C. Simple squamous
• D. Ciliated pseudostratified columnar

Hint:

Think about what the trachea must do every second: sweep mucus and trapped dust upward. That needs cilia.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We need to identify which epithelial tissue type lines the mucosa of the trachea in a normal, healthy adult.

Step 2: Key Formula or Approach:
Epithelium type in the airway is matched to its job: the trachea must move mucus and trapped particles up and out (mucociliary clearance), and different epithelial types are built for different jobs (protection from friction, stretching, or moving fluid).

Step 3: Detailed Explanation:
The tracheal mucosa is lined by ciliated pseudostratified columnar epithelium, often called "respiratory epithelium". It looks layered (hence "pseudostratified") but every cell actually touches the basement membrane, it just looks layered because the nuclei sit at different heights. The cells carry hair like cilia on their free surface, and goblet cells scattered among them make mucus. The cilia beat in one direction and sweep the mucus, along with trapped dust and germs, up toward the throat to be swallowed or coughed out. Transitional epithelium (option A) lines the urinary bladder and ureters, where it needs to stretch a lot, not the airway. Keratinized stratified squamous epithelium (option B) lines the skin, where its job is to resist wear and stop water loss, not to move mucus. Simple squamous epithelium (option C) is a single thin layer of flat cells, found in the alveoli and blood vessel linings, built for fast gas or fluid exchange, not for a mucus escalator.

Step 4: Final Answer:
The tracheal mucosa is lined by ciliated pseudostratified columnar epithelium, option (D).