Final answer:
Metaplasia involves the adaptation of cells to chronic stress by replacing one cell type with another via changes in gene expression and signal transduction pathways. Chronic irritation, inflammation, hormonal changes, and nutritional deficits are common causative factors.
Step-by-step explanation:
Metaplasia and Its Causes
The primary mechanism in metaplasia is the change in the phenotype of differentiated cells, usually as an adaptation to chronic stress or injury. This process involves the replacement of one differentiated cell type with another that can better survive the conditions. For example, in the respiratory tract, chronic irritation from smoking can cause normal columnar ciliated epithelial cells to be replaced with stratified squamous epithelial cells, which are more capable of withstanding the toxic environment. The trigger for metaplasia often involves alterations in signal transduction pathways and changes in gene expression, leading to the differentiation of stem cells or reprogramming of existing cells into a different cell type.
Causative factors for metaplasia include chronic irritation and inflammation, hormonal changes, and nutritional deficiencies, which can all induce signaling pathway alterations and consequent cell reprogramming. The development of metaplasia is a complex process involving various cellular processes such as cellular adhesion, migration, proliferation, and interactions with the extracellular matrix.