Professional and Linguistic Assessments Board (PLAB) Practice Exam

What type of metaplasia is characterized by changes from stratified squamous to columnar epithelium?

1. Adipose metaplasia

2. Columnar metaplasia

3. Squamous metaplasia

4. Respiratory metaplasia

The correct answer is: Columnar metaplasia

The transformation from stratified squamous epithelium to columnar epithelium is known as columnar metaplasia. This type of metaplasia commonly occurs in response to chronic irritation or inflammation, particularly in areas such as the respiratory tract or esophagus, where the normal squamous cells are replaced by columnar cells that may be better suited to the new environmental conditions. Columnar metaplasia is often seen in conditions such as gastroesophageal reflux disease (GERD), where the acidic environment prompts the squamous lining of the esophagus to undergo a change to a columnar type that can better withstand such irritation. This adaptation, while potentially protective, can also lead to pathological changes and conditions like Barrett's esophagus, which is a risk factor for esophageal cancer. The other options do not accurately describe this specific transformation: adipose metaplasia refers to the conversion of tissue to adipose (fat) tissue; squamous metaplasia generally describes the reverse process where columnar epithelium changes to squamous; and respiratory metaplasia typically refers to changes related to epithelial cells in the respiratory tract, but does not specifically denote a change from squamous to columnar.