Exam 2 · Week 3 · BIO 280 Pathophysiology
M3 · Cell Injury & Cancer
How cells adapt before they die, the difference between the two kinds of cell death, and what makes a tumor malignant.
▸M3Cell Injury & CancerWeek 3
💡 The one idea
A cell under stress adapts first and dies second. Every adaptation on this page is reversible if the stress is removed — which is exactly why catching it early matters.
Adaptation is survival. Death is what happens when adaptation runs out.
🥚 The five adaptations
| Change | What happens | Example |
|---|---|---|
| Atrophy | Cells shrink — less work, less blood, less stimulation | A limb in a cast; muscle after bed rest |
| Hypertrophy | Cells get bigger (not more numerous) | Cardiac muscle in hypertension; skeletal muscle with training |
| Hyperplasia | More cells | Endometrium under estrogen; BPH |
| Metaplasia | One mature cell type replaced by another that tolerates the stress better | Airway cells in a smoker; Barrett esophagus in reflux |
| Dysplasia | Disordered growth — abnormal size, shape and organization | Cervical dysplasia on a Pap. Pre-cancerous. |
Dysplasia is the turning point. The first four are orderly responses. Dysplasia is the cell losing the plot, and it is the step before malignancy.
🚨 Hypoxia is the most common cause of cell injury
No oxygen → no ATP → the sodium–potassium pump stops. Sodium and water flood in, the cell swells, and lysosomes rupture.
Other causes: physical and chemical agents, infection, immune reactions, genetic defects, nutritional imbalance, and free radicals. Reperfusion injury is the cruel one — restoring blood flow floods damaged tissue with oxygen and free radicals and can do more harm than the ischemia did.
☠️ Necrosis vs apoptosis
| Necrosis | Apoptosis | |
|---|---|---|
| Why | Injury — unplanned | Programmed — normal and controlled |
| Cell | Swells and bursts | Shrinks and is packaged up |
| Contents | Spill out | Stay contained, cleared by macrophages |
| Inflammation | Yes — always | No |
| Scale | Groups of cells | Single cells |
Types of necrosis worth knowing: coagulative (most solid organs after ischemia), liquefactive (brain, and abscesses), caseous (TB — cheese-like), fat (pancreatitis), gangrenous (limbs).
⭐ Benign vs malignant
| Benign | Malignant | |
|---|---|---|
| Growth | Slow | Rapid, unpredictable |
| Border | Encapsulated, well defined | Invasive, no capsule |
| Cells | Well differentiated — look like the parent tissue | Poorly differentiated (anaplastic) |
| Metastasis | Never | Yes — this is the defining feature |
| Recurrence | Rare after removal | Common |
Naming: -oma is usually benign (lipoma, adenoma).
Carcinoma = epithelial origin. Sarcoma = connective
tissue, bone, muscle. Leukemia / lymphoma = blood and
lymph. Exceptions that are malignant despite the ending: melanoma, lymphoma,
myeloma.
🧬 How cancer starts and how it spreads
Three steps: initiation (a mutation in the DNA), promotion (something makes the mutated cell divide), progression (it invades and metastasises).
- Oncogenes — the accelerator stuck on.
- Tumor suppressor genes (p53, BRCA) — the brakes, and they have failed.
Metastasis travels three ways: the bloodstream, the lymphatics, and direct seeding of a body cavity. The commonest destinations are lung, liver, bone and brain — they have the blood supply.
CAUTION — Change in bowel or bladder · A sore that does not heal · Unusual bleeding · Thickening or lump · Indigestion or trouble swallowing · Obvious change in a wart or mole · Nagging cough or hoarseness.
🎯 Module quiz
Questions for this module.
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