Pathology Cheat Sheet
Adapt, Age, or Progress
Cellular adaptations and ageing for NEET-PG: atrophy, hypertrophy, hyperplasia, metaplasia, dysplasia, telomere shortening, and replicative senescence.
MedNext Academy | 3 min read
Adapt, Age, or Progress
Cellular adaptations and ageing for NEET-PG: atrophy, hypertrophy, hyperplasia, metaplasia, dysplasia, telomere shortening, and replicative senescence.
Reversible cellular adaptations to stress and the molecular mechanisms of cellular ageing.
High-yield lines
- Hypertrophy is an increase in cell size without an increase in number and occurs in tissues with limited proliferative capacity such as cardiac muscle.
- Hyperplasia is an increase in cell number and requires cells capable of division, unlike neurons or cardiac myocytes.
- Metaplasia is the reversible replacement of one differentiated cell type by another through reprogramming of stem cells.
- Barrett oesophagus is glandular intestinal metaplasia of squamous mucosa caused by chronic acid reflux, with risk of adenocarcinoma.
- Squamous metaplasia of bronchial epithelium in smokers loses ciliary clearance and may progress to squamous cell carcinoma.
- Dysplasia is disordered maturation with nuclear atypia confined to the epithelium and is not invasion.
- Atrophy results from decreased protein synthesis and increased degradation through the ubiquitin-proteasome system and autophagy.
- Hyperplasia regresses when the stimulus is removed, which distinguishes it from autonomous neoplastic growth.
- Each cell division shortens telomeres, and critically short telomeres trigger replicative senescence known as the Hayflick limit.
- Telomerase maintains telomere length in stem and germ cells and is reactivated in most cancers to confer replicative immortality.
- Cellular ageing reflects accumulated DNA damage, telomere shortening, defective proteostasis, and mitochondrial decline.
- The most common cause of left ventricular hypertrophy is systemic hypertension producing pressure overload.
Mapped competency codes
- PA2.6
- PA2.7
Continue into the full chapter
This summary maps to PA2-cell-injury-and-adaptation.
Frequently Asked Questions
What is the difference between hypertrophy and hyperplasia?
Hypertrophy is an increase in cell size with the same number of cells, while hyperplasia is an increase in the number of cells; both can occur together in tissues capable of division.
What type of adaptation is Barrett oesophagus?
Glandular (intestinal) metaplasia, in which squamous oesophageal epithelium is replaced by columnar epithelium with goblet cells, carrying adenocarcinoma risk.
How does metaplasia differ from dysplasia?
Metaplasia replaces one normal mature cell type with another normal mature cell type, whereas dysplasia is disordered maturation with nuclear atypia.
What limits the number of divisions a somatic cell can undergo?
Progressive telomere shortening with each division, which eventually triggers replicative senescence, the Hayflick limit.
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