Metaplasia (1)

Metaplasia (1)

1. METAPLASIA Presented By: Maryam Manzoor Lecturer Pharmacology Rashid Latif College of Pharmacy

2. DEFINITION Metaplasia is a reversible change in which one adult cell type ( epithelial or mesenchymal ) is replaced by another adult cell type. A cell type sensitive to a particular stress is replaced by another cell type better able to withstand the adverse environment.

3. Metaplasia is thought to arise by the reprogramming of stem cells to differentiate along a new pathway. EXAMPLES Epithelial metaplasia -------------- smokers- ------ciliated columner epithelial cells of trachea are replaced by stratified squamous epithelial cells--------------- important protective functions like ciliary clearance of particulate matter is lost.

4. Squamous cells replace columnar cells

5. 2- Chronic gastric reflux-----------the normal stratified squamous epithelium of the lower esophagus converts to metaplastic gastric or intestinal-type columnar epithelium----- esophageal carcinoma. 3- In mesenchymal cells--------------- fibroblasts form osteoblasts and chondroblasts to form bone and cartilage.

6. UNDERLYING MECHANISM Metaplasia occurs from genetic reprogramming of stem cell. This genetic reprogramming is brought about by changes in signal generated by mixture of cytokines , growth factors, and extracellular matrix component in cell environment . The external signal induce specific transcription factors that lead the cascade of phenotype specific genes toward a fully differentiated cell. W hen stimulus stops metaplastic changes reverse.

7. The influences that induce metaplastic change in an epithelium , if persistent, may predispose to malignant transformation .

8. DYSPLASIA Atypical proliferative changes due to chronic irritation or inflammation Gradual loss of differentiation Morphological characteristics are lost. Premalignant change

9. Mild dysplasia Moderate dysplasia Marked dysplasia DYSPLASIA IN THE CERVIX

10. ANALPASIA Anaplasia is a condition of cells with poor cellular differentiation, losing the morphological characteristics of mature cells and their orientation with respect to each other and to endothelial cells. Complete loss of differentiation. irreversible Nuclei are large and disproportionate to the cell size.

11. HYPOPLASIA Incomplete development of an organ so that it fails to reach adult size. Similar to aplasia but less severe.

12. APLASIA Aplasia is a condition marked by the incomplete development, or absence, of an organ or tissue. Severe than hypoplasia. Occurs due to inherited genetic defects. EXAMPLES Aplastic anemia Thymic aplasia