AIM • STEP 10
3rd Year MBBS
Foundation
3rd Year MBBS
Foundation
Student Memory Support
Cellular Adaptation, Necrosis, Apoptosis and Cellular Ageing
High-yield memory reinforcement and last-minute revision for KMU 3rd Year MBBS.
1. High-Yield Flashcards
Tap each question to reveal the answer.
What is hypertrophy?
Increase in the size of individual cells due to increased synthesis of proteins and organelles.
What is hyperplasia?
Increase in the number of cells in a tissue capable of cell division.
What are the two major mechanisms responsible for cellular atrophy?
Reduced protein synthesis and increased protein degradation, with autophagy contributing to loss of cellular components.
How does metaplasia develop?
Persistent stress reprograms stem or precursor cells to differentiate into another mature cell type better able to tolerate the stress.
What does smooth endoplasmic reticulum hypertrophy indicate in hepatocytes?
Increased synthesis of drug-metabolizing enzymes in response to repeated chemical or drug exposure.
What are the three main nuclear changes seen in necrosis?
Pyknosis, karyorrhexis and karyolysis.
Why does coagulative necrosis temporarily preserve tissue architecture?
Protein and enzyme denaturation limits proteolytic digestion, allowing dead tissue outlines to remain recognizable.
Which necrotic pattern is characterized by extensive enzymatic digestion of tissue?
Liquefactive necrosis.
Which necrotic pattern is classically associated with tuberculosis?
Caseous necrosis.
What produces the chalky deposits seen in fat necrosis?
Fatty acids combine with calcium to form calcium soaps through saponification.
Which enzymes are central to apoptosis?
Caspases, including initiator and executioner caspases.
What key mitochondrial event occurs in the intrinsic apoptotic pathway?
Increased mitochondrial permeability causes release of cytochrome c into the cytoplasm.
How is the extrinsic apoptotic pathway initiated?
Binding of extracellular death ligands to cell-surface death receptors activates initiator caspases.
Why does apoptosis produce little inflammation?
Cellular contents remain enclosed within membrane-bound apoptotic bodies that are rapidly phagocytosed.
How does telomere shortening contribute to cellular ageing?
Critically shortened telomeres trigger permanent growth arrest and replicative senescence.
What does lipofuscin accumulation indicate in ageing cells?
Accumulated products of previous oxidative and lipid damage; it is a marker of cellular wear.
2. Mnemonics
Mnemonic Title: Major Cellular Adaptations
HHAM
Meaning: Hypertrophy, Hyperplasia, Atrophy, Metaplasia.
Mnemonic Title: Nuclear Changes in Necrosis
PKK
Meaning: Pyknosis → Karyorrhexis → Karyolysis.
Mnemonic Title: Major Mechanisms of Cellular Ageing
DTPN
Meaning: DNA damage, Telomere shortening, defective Protein homeostasis, altered Nutrient sensing.
3. Memory Tables
Hypertrophy vs Hyperplasia
| Feature | Hypertrophy | Hyperplasia |
|---|---|---|
| Main change | Increased cell size | Increased cell number |
| Cell division required | No | Yes |
| Major mechanism | Protein and organelle synthesis | Growth-factor/hormone-driven proliferation |
Necrosis vs Apoptosis
| Feature | Necrosis | Apoptosis |
|---|---|---|
| Cell size | Swelling | Shrinkage |
| Membrane | Disrupted | Remains intact around fragments |
| Cell contents | Leak out | Contained in apoptotic bodies |
| Inflammation | Prominent | Minimal or absent |
| Core mechanism | Severe irreversible injury | Caspase-mediated regulated death |
4. Rapid Revision Points — Last-Minute Revision
- Hypertrophy = increased cell size; hyperplasia = increased cell number.
- Atrophy results from reduced protein synthesis plus increased protein degradation.
- Metaplasia occurs through reprogramming of stem or precursor cells.
- Smooth-ER hypertrophy increases drug-metabolizing capacity.
- Necrosis causes membrane rupture, intracellular leakage and inflammation.
- Coagulative necrosis preserves tissue outline; liquefactive necrosis destroys it by digestion.
- Pyknosis → karyorrhexis → karyolysis is the classic nuclear sequence in necrosis.
- Intrinsic apoptosis involves mitochondrial permeability and cytochrome c release.
- Extrinsic apoptosis begins at cell-surface death receptors.
- Executioner caspases dismantle nuclear and cytoskeletal proteins.
- Ageing involves DNA damage, telomere shortening and impaired protein maintenance.
- Ageing reduces cellular functional reserve and the ability to respond to stress.
KMU Trap: Metaplasia is an adaptive and potentially reversible change in cell phenotype; it is not a form of cell death.
5. Clinical Memory Hooks
Long-standing hypertension → increased cardiac workload → myocardial hypertrophy.
Prolonged immobilization → reduced workload → skeletal muscle atrophy.
Chronic respiratory irritation → precursor-cell reprogramming → squamous metaplasia with loss of specialized function.
Ischemic injury in a solid organ → protein denaturation → coagulative necrosis with preserved tissue outline.
Severe DNA damage → intrinsic apoptotic pathway → mitochondrial cytochrome c release → caspase activation.
6. ⭐ High-Yield Exam Points
- ⭐ Hypertrophy is especially important in cells with limited ability to divide, such as cardiac myocytes.
- ⭐ Coagulative necrosis is typical of ischemia in most solid organs, while brain ischemia produces liquefactive necrosis.
- ⭐ Caseous necrosis is classically associated with tuberculosis.
- ⭐ Fat necrosis may produce calcium soaps by saponification.
- ⭐ Apoptosis causes cell shrinkage, chromatin condensation and apoptotic-body formation with minimal inflammation.
- ⭐ Intrinsic apoptosis is controlled at the mitochondria by BCL-2 family proteins and cytochrome c release.
- ⭐ Both intrinsic and extrinsic pathways converge on caspase activation.
- ⭐ Telomere shortening contributes to replicative senescence and reduced regenerative capacity with ageing.