Foundation - General Pathology Flashcards
Define hyperplasia
Increased number of cells due to increased functional demand
Define hypertrophy
Increased size of cells due to increased functional demand
Define hypoplasia
Decreased number of cells (involution) due to decreased functional demand
Define atrophy
Decreased size of cells due to decreased functional demand
Explain how atrophy could arise
- Lysosome autophagy of worn out organelles
- Ubiquitin-proteosome degradation of cytoskeleton
Explain what happens during autophagy
- Lysosome eats its own worn-out organelles
- Formation of residual bodies
- Residual bodies may accumulate as lipofuscin (wear and tear pigments)
Explain the importance of autophagy
- Eliminate abnormal molecules that may be toxic
- Recycling of components for survival
Define metaplasia
Change in cell type due to change in stress (via reprogramming of stem cells)
Describe the reversible, early stage changes when a cell undergoes stress
Stress = swell
1. Swelling of cytoplasm
2. Fatty changes
3. Nuclear chromatin clumping
4. Mitochondrial and ER swelling
Protein-related
5. Increased expression of protective proteins (e.g. molecular chaperons that protect cell from further damage, ubiquitin that tag damaged proteins for proteolysis)
6. Formation of aggregates of ubiquitin and damaged proteins aka inclusion bodies
Describe the irreversible, late stage changes when a cell is about to undergo apoptosis
- Nuclear condensation/shrinkage → pyknosis
- Nuclear break up → karyorrhexis (karyotype + ex)
- Nuclear dissolution → karyolysis (karyotype + lyse)
- Lysosome rupture
- Amorphous densities in mitochondrial matrix (mitochondria messy and dense)
- Disruption of cell membrane
Describe the main mechanisms of cellular injury/stress
- Cell membrane damage
- Mitochondrial damage
- Ribosomal damage
- Nuclear damage
The consequences of cell injury depend on:
- Time of exposure
- Severity of injury
- Type of injury
State the types of cell death
- Autophagy
- Autolysis
- Necrosis
Define autolysis
Death of cells and tissues after death of whole organism by post-mortem release of digestive enzymes from lysosomes
Define necrosis
Death of body tissues when there is inadequate perfusion/too little blood flowing through it (due to pathological reasons)
Distinguish between apoptosis and necrosis
- Apoptosis involves fewer cells; necrosis involves more cells
- Membrane intact for apoptosis but completely disrupted for necrosis
- Apoptosis is active process; necrosis is passive
- Apoptosis is never with inflammation but necrosis is usually
- Apoptosis is mostly physiological but necrosis is always pathological
- Apoptosis involves controlled dissolution of nucleus; necrosis involves fragmentation of nuclear DNA into nucleosomes
- During apoptosis, cell contents are released in apoptotic bodies within cell but during necrosis, cell contents freely leak out of the cell
State the physiological functions of apoptosis
- Regulating the number of cells in a tissue/organ
- Deletion of self-reactive cells (e.g. lymphocytes) to prevent autoimmunity
- Shedding of endometrial cells in menstrual cycle
Describe the morphological features of cells undergoing apoptosis
Mid-stage: highly eosinophilic due to denatured proteins
Late-stage: very pink, condensed nucleus
Briefly describe the process of necrosis
- Release of hydrolytic enzymes from damaged lysosomes
- Digestion and denaturation of cellular proteins
- Breakdown of cell membrane
- Contents like intracellular enzymes leak freely out of the cell
- Cessation of cell function
- Initiation of inflammatory response
Define anoikisis
When epithelial cells detach from neighbouring cells and ECM during apoptosis/programmed cell death
Define granuloma and its contents
Core of necrosis
1. Epithelioid macrophages (formed when macrophages from tissue stroma fail to engulf the offending agent)
2. Lymphocytes, neutrophil infiltration
3. Multinucleated Langhans giant cells (formed by fused epithelioid macrophages)
Classify the types of necrosis
- Coagulative necrosis
- Haemorrhagic necrosis
- Caseous necrosis
- Suppurative necrosis
- Liquefactive necrosis
- Fat necrosis
- Gangrenous necrosis
- Fibrinoid necrosis
Describe the pathogenesis of coagulative necrosis
Some occlusion → ischaemia → infarction → coagulative necrosis
List the classical presentations of coagulative necrosis
- Affects cell far from blood vessels or solid organs, usually occurs in heart, lungs, liver
- Appears white coz no blood
- GHOST CELLS (intact cytoplasm but no nucleus)
- Cell retains its architecture even with necrosis
Describe the pathogenesis of haemorrhagic necrosis
ENDPOINT: leakage of blood into surrounding tissues
E.g. 1 Occlusion of one blood supply → ischaemia → infarction including endothelium lining vessels of 2nd blood supply → loss of endothelial integrity of 2nd blood vessel → extravascular leakage into surrounding tissues
E.g. 2 Venous congestion → increased pressure → rupture of blood vessels → extravascular leakage
List the classical presentations of haemorrhagic necrosis
- Appears red coz blood flow out
- Affects organs with dual perfusion (e.g. liver, lungs)
Describe reperfusion injury
Reperfusion of ischaemic tissue worsens tissue hypoxic injury due to persisting endothelial defects
Describe the pathogenesis of liquefactive necrosis
Injury/infection/stroke → cell death of glial cells and neurons → myelin sheath breakdown → gelatinous, viscous liquid rich in fats → abscess formation → impaired blood flow