Cellular Adaptation. Adaptation generally means change for good. In the case of cells, change is not always beneficial.
dysplasia disorderly growth of cells. replacement by morphologically abnormal cells
atrophy - loss of cell volume OR reduction in cell number
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
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.
metaplasia - cells are replaced. conversion of one cell type to another. meta meaning beside. reversible
Aplasia - decrease in cell number
neoplasia - abnormal cell division, leading to cancer and tumours.
(1) atrophy - due to being immobile.
(3) ischemia - will eventually cause cell death but will also cause cellular atrophy
endocrine stimulation
(4) inadequate nutrition/nutrient starvation
physiological aspects of atrophy
aging. example, the thymus gland in early adulthood. the uterus after menopause
pathologic aspects of atrophy
chronic ischemic - an interruption in blood supply
a spinal injury leading to lower limb atrophy
extra cell material is disposed of by autophagic vacuoles which isolate and destroy organelles. some material stays and remains as residual bodies (ex. brown pigment / lipofuscin / age spots).
(2) denervation
(5) persistent cell injury
- 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
example, aplastic anemia - cessation of production of blood cells
associated with benzene, antibiotic toxicity, radiation, and other unknown factors.
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
pathologic hyperplasia abnormal proliferation of cell growth ---> can lead to malignant cell growth
physiologic hyperplasia - found in the sex organs during puberty
click to edit
both hypertrophy and hyperplasia lead to increase in tissue and organ mass, but by differing means
thyroid or prostate growth
- 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
- cells are abnormal in appearance (in size, shape, and arrangement). implies tissue may become neoplastic as they have potential to turn into cancerous cells
- occurs often in hyperplastic squamous epithelium
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.
example - screening of women for cervical cancer when scarping cervix to look for dysplasic cells.
does not mean cancer - it is an abnormal cell at the morphological level. it means there is an increased risk for cancer but that it is not a sure thing
can be pathological and physiological
heterotopia - replacement by foreign cell type due to disturbed differentiation
pseudo metaplasia a change in cuboid epithelium to another type due to pressure - just need to know the name.
For example --> when a nucleaus swells up and fills the entire cell that is abnormal and thus dysplasic