Exam 4: Metaplasia Flashcards
What is metaplasia?
Differentiated cells of one type are replaced by a different kind
What is modulation?
Mild phenotypic reversible change of cells in which they temporarily adapt to some new need but remain identifiable as members of their cell type
What are the types of metaplasia?
Epithelial
Connective tissue
What is the etiology of epithelial metaplasia?
Usually due to protracted mechanical trauma or prolonged inflammation
Another cause is hypovitaminosis A
Hormonal imbalance is also a potential cause
What is the pathogenesis of epithelial metaplasia?
Appears to be a protective mechanism wherein gradual changes occur in the proliferating layer of cells over several generations of mitosis until the adult cell derived from this layer is completely changed in type
What is the most common type of change with epithelial metaplasia?
From columaner cells to stratified squamous cells
What are the most common sites of epithelial metaplasia?
Urogenital tract
Respiratory tract
Lining of the ducts of glands
What are the effects of epithelial metaplasia?
Most serious effect is interference with flow of secretions or excretions
May function as a nucleus for concretion formation
Can be precancerous
What is the etiology of connective tissue metaplasia?
Mesenchymal tissues of the body may transform into more highly differentiated cell types
What is the effect of connective tissue metaplasia?
May play in the inflammatory process as an aid to overcoming the irritant and in healing
Often accompanies certain tumor conditions, especially mammary tumors of the canine
What are the mechanisms of metaplasia?
Indirect metaplasia
Direct metaplasia
What is indirect metaplasia?
Progenitor cells stop producing type A cells and switch to producing type B cells
Most common mechanism of mammals
What is direct metaplasia?
Type A cells change into type B cells which is a type of metamorphosis
Evidence is based mostly on research
Which types of cells are better at metaplasia?
In most mammals, it is an event within epithelium and mesenchymal tissues
