Response to Injury I Flashcards
What is cell response based on?
The type of response a cell undergoes is based on the type, duration and severity of the noxious stimulus.
The type of response a cell undergoes is based on is cell type, status within the cell cycle, capability to regenerate in turn its genetic profile.
What are the different cell types?
Labile
Stable
Permanent
Define labile cells.
Labile: continually in the cell cycle eg: cells of the epidermis. More susceptible to adaptation.
Define stable cells.
Stable: temporarily exit the cell cycle can be recruited back in eg: liver cells
Define permenant cells.
Permanent: permanently differentiated once lost cannot be replaced eg: cells of the central nervous system, axons, cardiac myocytes. More susceptible to cell death.
What happens when a cell is injured?
Following injury molecular and genetic changes will proceed with functional change. Then structural changes then signs and symptoms.
Adaptative changes may be due to pathological and physiological changes.
Give examples of cellular adaptive response.
Hyperplasia
Hypertrophy
Atrophy
Metaplasia
Dysplasia
Define Hyperplasia.
Increase in the number of cells occurs in tissues capable of cell division.
Eg: proliferation of glandular tissue in puberty/pregnancy or in the case of the prostate during hormonal imbalance. Dental relevance – can be seen in chronic hyperplastic candidiasis.
Define hypertrophy.
Increase in the size of cell.
Eg: skeletal or cardiac muscles. Pathological examples of this is left cardiac hypertrophy following heart failure.
Define atrophy.
Reduction in the size of an organ as a result of the reduction in the number of cells.
Eg: vaginal epithelium undergoes atrophy during menopause.
Define metaplasia.
Change from one differentiated cell type to another differentiated cell type.
Define dysplasia.
Disordered stratification and maturation.
Which cellular adaptive response is reversible.
Hyperplasia, hypertrophy, atrophy and metaplasia are all reversible response once stimulus is removed.
Metaplasia may proceed dysplasia (too a degree is reversible and genetic change leaves it irreversible).
Give examples of Causative agents of cell injury.
*Physical – E.g. trauma, thermal, radiation
*Chemical – E.g. CO, cigarette smoke, ethanol
*Infectious – E.g. toxins, metabolic products, lysis, DNA damage
*Oxygen deprivation – E.g. hypoxia, ischaemia
*Immunologic – E.g. complement activation, cell mediated cytotoxicity, autoimmune
Explain the mechanism of cell injury through ATP depletion.
Most important target of cell injury is disruption of metabolism, through ATP depletion frequently arise from hypoxia.
Mitochondrion is also prone to damage from injury, due to influx of calcium or generation of reactive oxygen species and hypoxic states.