General Pathology Flashcards
An increase in stress on an organ leads to
Increase in organ size via:
- Hypertrophy
- Hyperplasia
A decrease in stress on an organ leads to
Atrophy
A change in stress leads to
Metaplasia (change in cell type)
Mechanism(S) involved in hypertrophy
- Gene activation
- Protein Synthesis
- Production of organelles
Mechanisms involved in hyperplasia
New cells from stem cells
Mechanism involved in metaplasia
Reprogramming of stem cells
Cells that cannot undergo hyperplasia
- Cardiac cells
- Skeletal muscle
- Neurons
Decrease in the number of cells occur via
Apoptosis
Decrease in cell size occur via
Ubiquitin proteosome degradation of cytoskeleton and autophagy of cellular components
Metaplasia involves change in
One surface epithelium to another (squamous, columnar, or urothelial)
Is metaplasia reversible or irreversible
Reversible
Which vitamin deficiency can result in metaplasia
Vit.A deficiency
Example of mesenchymal tissue that can undergo metaplasia
Muscle: myositis ossificans (connective tissue within muscle changes to bone during healing or trauma)
Dysplasia
Disordered cell growth
Aplasia
Failure of cell production during embryogenesis
Hypoplasia
Decrease in cell production during embryogenesis, resulting in a relatively small organ (streak ovary in Turner Syndrome)
When does cellular injury occur
When a stress exceeds a cells ability to adapt
Common causes of cellular injury
Inflammation Nutrition deficiency or excess Hypoxia Trauma Genetic mutations
What is hypoxia?
Low oxygen delivery to tissue
What is the function of oxygen in the ETC
Act as a electron acceptor
Consequence of impaired oxidative phosphorylation
Decreased ATP
Consequences of low ATP
Disruption of:
- Na/k pump, resulting in sodium and water buildup in the cell
- Ca2+ pump, resulting in high cytosolic ca concn. (Enzyme activation)
- Aerobic glycolysis, resulting in switch to anaerobic glycolysis. Lactic acid buildup results in low pH, which denatures proteins and precipitates DNA
Causes of hypoxia
Ischemia
Hypoxemia
Decrease o2 carrying capacity
What is Ischemia
Decrease blood flow through an organ
Causes of ischemia
- Decrease arterial perfusion (atherosclerosis)
- Decrease venous drainage (Budd-Chiari Syndrome)
- Shock (generalized HypoTN resulting in poor tissue perfusion)
What is hypoxemia
Low partial pressure of oxygen in blood (PaO2 <60mm Hg, SaO2 <90%)
Causes of hypoxemia
- High altitude: decrease ATM pressure, decrease PAO2
- Hypoventilation: increased PACO2, decreased PAO2 (COPD)
- Diffusion defect: cannot push O2 into blood due to thick barrier
- V/Q mismatch : blood bypasses oxygenated lung (right to left shunts); oxygenated air cannot reach blood (atelectasis)
Causes of decrease O2 carrying capacity
Hb loss or dysfunction:
- Anemia (decrease RBC mass) normal PaO2 & SaO2
- Carbon monoxide poisoning: binds more avidly to Hb (decr. SaO2)
- Methemoglobinemia: Fe3+ cannot bind O2 (decr. SaO2)
CO poisoning C/F
Cherry- red skin
Early sign of CO exposure
Headache
Methemoglobinemia
When Fe2+ is oxidized to Fe3+ which cannot bind O2
Causes of metHB
- Oxidant stress: sulfa and nitrate drugs or newborn
C/F of methemoglobinemia
Cyanosis with chocolate colored blood
Treatment for methemoglobinemia
Methylene blue (reduces Fe3+ back to Fe2+)
Hallmark of reversible cellular injury
- Cytosolic swelling: effacement of microvill &membrane blebs
- rER swelling: decrease protein synthesis
Hallmark of irreversible cellular injury
Membrane damage:
- Plasma membrane: enzymes leak, calcium enters cell
- Mitochondrial membrane: loss of ETC (IMM), cytochrome c leaks
- Lysosomes membrane: enzymes leak and become activated by high intracellular calcium
