Flashcards in 14. Cellular Adaptation Deck (24):
what kind of changes does cellular adaptation include?
4. metabolic activity
why do cells need to adapt?
due to changes in the environment or demand
what is the purpose of cellular adaptation?
to acquire a new, steady state of metabolism and structure
better equips cells to survive in a new environment
failure of adaptation may lead to sub-lethal or lethal cell injury
what determines a cell's susceptibility to damage?
the type of cell it is -
labile and stable populations adapt easily due to active stem cell population
some cells don't need to adapt, they survive severe metabolic stress without harm
permanent cells cannot adapt, they are terminally differentiated and have a highly specialised function. easily damaged by environmental change
what are the 2 types of cellular adaptation?
physiological - responding to normal changes in physiology or demand
pathological - responding to disease related changes
what are the 3 types of cellular adaptive response?
1. increased cellular activity
2. decreased cellular activity
3. change of cell function and morphology
how can cells increase activity?
1. hypertrophy- increases synthesis of structural components and metabolism. characteristic of permanent cell populations (cardiac and skeletal muscles)
2. hyperplasia - possible in stable and labile populations
these 2 can co-exist.
these 2 don't only exist on a cellular level, sub-cellular components can also become enlarged
how can cells reduce activity?
decrease size of cells
decrease number of cells
what is atrophy?
reduction in size of an organ or tissue by decrease in cell size and number. this can either be physiological or pathological
BUT not all reduced cell mass is due to atrophy, it can also be related to developmental abnormalities
examples of pathological atrophy
1. decreased workload - disuse atrophy
2. loss of innervation - denervation atrophy
3. diminished blood supply
4. inadequate nutrition
5. loss of endocrine stimulation
what are the mechanisms of atrophy?
1. reduction in volume of individual cells, leaving behind a residual body
2. death of individual cells, via apoptosis or involution
what is involution?
physiological atrophy by apoptosis
what is metaplasia?
transformation of one differentiated cell type into another
eg. transdifferentiation of stem cells
what is the consequence of metaplasia?
better adaptation to new environment
it may form the basis on which neoplasia develops
which tissues can adapt by metaplasia?
epithelium and mesenchymal tissues
is metaplasia physiological or pathological?
what metaplastic effect does cigarette smoke have on the body?
pseudo stratified ciliated cells of the airway -> squamous
what metaplastic effect do calculi, bladder catheters and schistosomiasis have on the body?
transitional epithelium -> squamous
what metaplastic effect does chronic trauma have on the body?
fibrocollagenous tissue -> bone
what metaplastic effect does acid reflux have on the body?
squamous -> columnar
what is dysplasia?
the enlargement of an organ or tissue by the proliferation of cells of an abnormal type, as a developmental disorder or an early stage in the development of cancer. it is the earliest morphological manifestation of multistage process of neoplasia
is dysplasia reversible or irreversible?
what is the difference between dysplasia and malignancy?
it is an in-situ disease, non-invasive
shows cytological features of malignancy but there is no invasion