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Cellular Adaptation. Adaptation generally means change for good. In the…
Cellular Adaptation. Adaptation generally means change for good. In the case of cells, change is not always beneficial.
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hyperplasia - increase in cell number due to an increased rate of division. Not due to an increased size of individual cells. Only cells capable of dividing become hyperplasic
compensatory hyperplasia occurs when tissues have lost their mass. example - in the liver toxicity can lead to death of hepatocytes - hyperplasia leads to their replacement
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hypertrohpy - increased cell size, usually due to a net increase in cellular protein content, NOT an increase in cell number. Hypertrophy is a cellular response due to increased cell demand.
- there is an increased workload placed on the cell.
physiologic hypertrophy Example - when you work out your muscle cells increase in size b/c the number of contractile filaments increases. organelles such as mitochondria also may increase
- hypertrophy involves DNA and protein synthesis
pathologic hypertrophy Example, in the heart when increased myocardial mass can occur, leading to heart muscle fatigue, eventual heart failure. known as cardiac hypertrophy
causes include: hypertension, infectious processes, hormonal stimuli
both hypertrophy and hyperplasia lead to increase in tissue and organ mass, but by differing means
metaplasia - cells are replaced. conversion of one cell type to another. meta meaning beside. reversible
- it's considered an adaptation to a hostile environment
- example, in the respiratory tract when columnar goblet cells are replaced by stratified squamous epithelium which are better suited for environmental irritation
- some metaplasia is related to maglignant activities
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pseudo metaplasia a change in cuboid epithelium to another type due to pressure - just need to know the name.
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neoplasia - abnormal cell division, leading to cancer and tumours.
KEY POINTS:
- adaptive cellular responses indicate cellular stress caused by altered functional demand or chronic sublethal injury
- hypertrophy and hyperplasia are generally a result of increased functional demand
- atrophy results from decreased functional demand or chronic ischemia
- metaplasia and dysplasia result from persistent injury
neoplasia - means new growth. it implies abnormality of cellular growth and may be used interchangeably with the word tumour.