Metaplasia occurs in all of the following except:
Correct Answer: Stem cells
Description: Ref: Chapter 1. Cellular responses to stress and toxic insults; page: 11: Robbins and Cot ran Pathologic Basis of Disease: 8th editionExplanation:Metaplasia is the results of reprogramming of stem cells that are known to exist in normal tissues, or of undifferentiated mesenchymal cells present in the connective tissue.Metaplasia is a reversible adaptive change in which one differentiated epithelial cell type is replaced by another epithelial cell type of mature type.Example of columnar to Squamous Metaplasia: in chronic smokers, the normal ciliated columnar epithelial cells of trachea and bronchi are replaced by squamous cells.Example of Squamous to columnar Metaplasia: in Barrett esophagus, in which esophageal Squamous epithelium is replaced by intestinal like columnar cells under the influence of refluxed gastric acid.Transitional /uro-epithelium can also undergo Squamous Metaplasia by chronic irritation like in urinary bladder stones.Hence, Metaplasia is basically due to reprogramming of stem cells as adaptive mechanism.Metaplasia is basically classified into two types:- Epithelial Metaplasia- Mesenchymal Metaplasia.The epithelial cells can undergo Metaplasia due to chronic irritation, if they have stem cell reserve component.Mesenchymal Metaplasia is rare: example is Myositis Ossificans, where muscles will undergo chondroid Metaplasia due to improper fracture healing.
Category:
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