Autopsy of lung of an old man shows that the bronchi are lined by stratified squamous epithelium. What is this change –
**Core Concept**
The underlying principle being tested is the process of **metaplasia**, a condition where one type of epithelium is replaced by another, often in response to chronic irritation or injury. In the context of the lung, the normal **ciliated pseudostratified columnar epithelium** lining the bronchi can undergo metaplastic changes.
**Why the Correct Answer is Right**
The correct answer is related to **squamous metaplasia**, a condition where the normal epithelial lining of the bronchi is replaced by **stratified squamous epithelium**. This change is often seen in response to chronic irritation, such as smoking or chronic inflammation, and can be a precursor to more serious conditions.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because it does not accurately describe the metaplastic change observed.
**Option B:** This option is also incorrect as it refers to a different type of cellular change.
**Option C:** This choice is incorrect because it describes a type of tissue change not relevant to the given scenario.
**Option D:** This option is incorrect as it refers to a different pathological process.
**Clinical Pearl / High-Yield Fact**
Squamous metaplasia in the lung is a significant finding, as it can be a precursor to **squamous cell carcinoma**. Recognizing this change is crucial for early detection and management of lung cancer.
**Correct Answer:** D. Squamous metaplasia.