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Summary Robbins Basic Pathology - Chapter 2

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Summary Chapter 2 - Cell Injury, Cell Death and Adaptations of Robbins Basic Pathology 10th edition.

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  • Hoofdstuk 2
  • May 23, 2020
  • 12
  • 2019/2020
  • Summary

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Overview of cellular responses to stress and noxious stimuli
 Adaptation
o Caused by physiological stresses and potentially injurious conditions
o Result is a new steady state and preserving viability and function
 Cell injury
o Caused by exceeded adaptive capability or harmful/excessive external stress
o Results in reversible injury → cell can return to stable baseline
o Results in irreversible injury, when stress is severe, persistent or rapid in
onset
 Cell death
o Caused by irreversible injury, ischemia (lack of blood flow), infections, toxins
and immune reactions.
o Also, normal and essential process in embryogenesis and maintenance of
tissue homeostasis

Causes of cell injury
 Hypoxia and ischemia
o Hypoxia = oxygen deficiency
 Anemia or CO poisoning
 Ischemia = reduced blood supply
 Arterial obstruction → ischemia → hypoxia
 Results in deficiency of essential nutrients and buildup of toxic
metabolites
 Toxins
 All substances used excessively or inappropriately can be toxic
 Air pollutants, insecticides, CO, cigarette smoke, ethanol, glucose, salt,
water and oxygen
 Infectious agents
 All types of disease-causing pathogens
 Viruses, bacteria, fungi and protozoans
 Immunologic reactions
 Autoimmune reactions against one's own tissues
 Allergic reactions against environmental substances
 Excessive or chronic immune responses to microbes
 Elicit inflammatory reactions, which are often the cause of damage to
cells and tissues
 Genetic abnormalities
 Can result in pathologic changes
 Congenital malformations as in Down Syndrome
 Single amino acid substitution in hemoglobin giving rise to sickle cell
anemia
 May cause cell injury as a consequence of deficiency of functional
proteins
 Enzymes in inborn errors of metabolism, accumulation of damaged
DNA or misfolded proteins → all trigger cell death when beyond repair

 Nutritional imbalances
o Protein-calorie insufficiency → cell injury
o Specific vitamin deficiencies
o Excessive dietary intake may result in obesity → type 2 diabetes and
atherosclerosis
 Physical agents
o Trauma, extremes of temperature, radiation, electric shock and sudden
changes in atmospheric pressure → wide range of effects

,  Aging
o Cellular senescence results in a diminished ability of cells to respond to stress
and eventually, the death of cells and of organism.
Sequence of events in cell injury and cell death
Reversible Cell Injury
Reversible injury is the stage of cell injury at which the deranged function and morphology of
the injured cells can return to normal if the damaging stimulus is removed.
 Failure of energy-dependent ion pumps → inability of maintaining ionic and fluid
homeostasis → taking in too much water → swollen cells
 Degenerated organelles and lipids may accumulate inside the injured cell
 Induce specific alterations in cellular organelles
o Smooth ER is involved in metabolism of various chemicals
o Cells exposed to these chemicals show hypertrophy (increase in volume) of
ER → adaptive response → important functional consequences.
o Cells adapted to one drug demonstrate an increased capacity to metabolize
other compounds handled by the same system.
 With persistent or excessive noxious exposure → point of no return → cell
death
o If biochemical and molecular changes that predict cell death can be identified,
the transition from reversible to irreversible can be prevented
 No definitive morphological or biochemical correlates of irreversibility,
but characterized by three phenomena
1. Inability to restore mitochondrial function
2. Loss of structure and functions of plasma membrane
and intracellular membranes
3. Loss of DNA and chromatin structural integrity
Morphology
 Cellular swelling → increased permeability of plasma membrane. Causes pallor,
increased turgor and increase in organ weight.
 Fatty change → appearance of triglyceride containing lipid vacuoles. Involved in lipid
metabolism.
 Plasma membrane alterations → blebbing, blunting or distortion of microvilli
 Mitochondrial changes → swelling and phospholipid rich amorphous densities
 Dilation of ER → detachment of ribosomes and dissociation of polysomes
 Nuclear alterations → clumping of chromatin

Cell Death
When cells are injured, they die by different mechanisms, depending on the nature and
severity of the insult.
 Severe disturbance (loss of oxygen and nutrients supply or action of toxins) cause a
rapid and uncontrollable form of death called accidental cell death
o Accidental cell death = necrosis
o Commonly encountered injuries, resulting from ischemia, exposure to toxins,
infections and trauma.
o Inevitable end result of severe damage that is beyond salvage and is not
thought to be regulated by specific signals or biochemical mechanisms
o Happens accidentally, because injury is too severe to be repaired
 When the injury is less severe, or cells need to be eliminated during normal
processes, they activate a precise set of molecular pathways that culminate in
death.
o These cell deaths can be manipulated by therapeutic agents of genetic
mutations
o Regulated cell death → apoptosis
o Necroptosis → some features of necrosis and apoptosis

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