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Pathological Processes > 1. Cell Injury > Flashcards

1. Cell Injury Flashcards

1
Q

Outline the different branches of pathology.

A 
Medical microbiology
Chemical pathology
Haematology 
Immunology
Cellular pathology - histopathology & cytopathology
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2
Q

What is the difference between histopathology and cytology?

A

Histopathology is the assessment of tissue samples, whereas cytology specimens are disaggregated cells which have been scraped or sucked off (NOT tissues).

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3
Q

What fixative is commonly used to process tissue samples?

A

Formalin

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4
Q

Outline some of the advantages of using cytology rather than histopathology.

A
  • Non-invasive or minimally invasive
  • Fast
  • Cheap
  • Generally safe
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5
Q

Outline some of the limitations of cytology.

A
  • Higher error rates

- Used to confirm or exclude cancer than than give a diagnosis

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6
Q

Outline some advantages of using histopathology rather than cytology.

A
  • The architecture of the tissue can also be assessed
  • Differentiate between in situ and invasive malignancy
  • Able to assess completeness of an excision (e.g of a cancer)
  • More complete grading and staging of a cancer
  • Better for immunological and molecular testing
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7
Q

What is the function of tissue fixation?

A

Block autolysis (breakdown of the tissue) :

  • inactivating the tissue enzymes
  • preventing bacterial growth
  • harden tissue
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8
Q

What component of the cell does haematoxylin stain? What colour will this be?

A

Nuclei purple

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9
Q

What does eosin stain? What colour?

A

Cytoplasm and connective tissue, Pink

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10
Q

What is immunohistochemistry used to detect?

A

The prescience of specific substances, usually proteins, by labelling them with antibodies.

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11
Q

How does immunohistochemistry work?

A

Antibodies are used to detect a specific protein or antigen, these are usually conjugated to an enzyme that catalysed a colour-producing reaction. This is usually brown.

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12
Q

Suggest some useful antigenic substances that can be detected using immunohistochemistry.

A
  • Actin, to identify SM cells
  • Cytokeratins, to identify epithelia, fibrous proteins
  • Micro-organisms
  • Hormone receptors, ER and PR
  • HER 2, growth factor receptor
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13
Q

When might it be appropriate to request frozen sections?

A

During an operation, when the result will influence the course of the operation.

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14
Q

What is a disadvantage of using emergency frozen sections?

A

The results are harder to interpret, so it has increased rate of errors and false negatives

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15
Q

Name and describe the 4 causes of hypoxia

A
  1. Hypoxaemic - arterial oxygen content is low
  2. Anaemic - decreased ability of Hb to carry oxygen
  3. Ischaemic - interruption to blood supply
  4. Histiocytic - inability to use oxygen is cells due to disabled oxidative phosphorylation enzymes
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16
Q

What is hypoxia?

A

Oxygen deprivation

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17
Q

Other than hypoxia, what other agents can cause cell injury or death.

A
  1. Physical agents - direct trauma, extreme temperature changes, radiation
  2. Chemical agents and drugs - alcohol
  3. Micro-organisms - bacteria, virus,etc
  4. Immune mechanisms
  5. Dietary insufficiencies or excess
  6. Genetic abnormalities - inborn errors in metabolism
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18
Q

Which 4 cellular components are the principle targets of cell injury?

A
  1. Cell membranes
  2. Nucleus
  3. Proteins- structural proteins and enzymes
  4. Mitochondria
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19
Q

Summarise the steps involved in a hypoxia cell injury.

A
  1. Cell is deprived of oxygen
  2. Mitochondrial ATP production stops
  3. Na+/K+ ATPase pump cannot work
  4. Na+ and water seep into the cell
  5. Cell swells and membrane stretches
  6. Glycolysis is increased
  7. Heat-shock response is initiated
  8. pH decreases as lactate build up
  9. Calcium influx into the cell
  10. Activation of enzymes
  11. ER and organelles swell
  12. Enzymes leak out of lysosomes and attack cytoplasmic components
  13. Cell membranes damaged and show blebbing
  14. Cell death
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20
Q

What enzymes does calcium activate during cell injury?

A

Phospholipases
Proteases - damage cytoskeletal structures and membrane proteins
ATPase - further deplete ATP
Endonucleases - nuclear chromatin clumping

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21
Q

At what stage does prolonged hypoxia damage become irreversible?

A

Mass influx of calcium and activation of destructive enzymes.

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22
Q

What are free radials?

A

Reactive oxygen species

Single unpaired election in their outer shell, making them unstable and hence incredible reactive.

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23
Q

Which 3 free radicals are of particular significance in cells?

A
  • Hydroxyl (OH) = the most dangerous
  • Superoxide (O2-)
  • Hydrogen peroxide (H2O2)
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24
Q

How are free radicals produced?

A
  • normal metabolic reactions
  • inflammation: oxidative burst of neutrophils
  • radiation (H20 to OH’)
  • Fenton reaction
  • Drugs and chemicals
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25
Q

Outline 3 mechanisms that the body uses to control free radicals.

A

Anti-oxidant system:

  1. Enzymes - SOD, catalase, peroxidase
  2. Free radical scavengers - Vit A,C,E, glutathione
  3. Storage proteins that sequester transition metals in EC matrix.
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26
Q

How does superoxide dismutase act as an anti-oxidant?

A

Catalyses the reaction of superoxide to hydrogen peroxide, which is significantly less toxic to cells.

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27
Q

How do catalases and peroxidases form part of the anti-oxidant system?

A

They complete the process of free radical removal.

Catalyse the reaction of H2O2 to oxygen and water.

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28
Q

Name 2 examples of sequester proteins and describe their function.

A

Transferrin and ceruloplamin sequester iron and copper, which catalyse the formation of free radicals.

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29
Q

What is ischaemia-reperfusion injury?

A

When blood flow is returned to an ischaemic tissue which is not yet necrotic, it can cause injury that is worse than if the blood flow was not restored.

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30
Q

What 3 mechanisms may explain ischaemia - reperfusion injury?

A
  1. Increased production of free radicals with reoxygenation.
  2. Increased number of neutrophils, more inflammation and tissue injury
  3. Delivery and activation of complement pathway
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31
Q

How do free radicals injure cells?

A
  1. Damage lipids in cell walls by lipid peroxidation, generating an autocatalytic chain reaction .
  2. Oxidase proteins, carbohydrates and DNA
    - molecules become bent, broken or cross linked
  3. Mutagenic and carcinogenic
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32
Q

How do heat shock proteins contribute to the cells protective response against injury?

A

They are activated during stress or damage and aim to repair mis-folded proteins to maintain cell viability.

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33
Q

Give an example of a heat shock protein.

A

Ubiquitin.

34
Q

What 3 changes would be visible in a dying or injured cell under a light microscope?

A
  1. Cytoplasmic changes - pale and swollen
  2. Nuclear changes - pyknosis, karyolysis or karyorrhexis
  3. Abnormal cellular accumulations
35
Q

What is the difference between pyknosis, karyolysis and karyorrhexis?

A

Pyknosis - condensation of nucleus to dark mass
This is followed by…
Karolysis - nucleus disappears due to chromatin dissolution
Karyorrhexis - fragmentation of the nucleus

36
Q

What changes would be visible under an electron microscope in REVERSIBLE cell injury?

A
  • swelling of cell and organelles
  • cytoplasmic blebs
  • clumping of nuclear chromatin
  • ribosome detachment
37
Q

What changes would be visible through an electron microscope during IRREVERSIBLE cell injury?

A
  • Increased swelling
  • Nuclear changes - pyknosis, karyolysis or karyorrhexis
  • myeline figures and membrane defects
  • Lysosome rupture
  • ER lysis
38
Q

Compare Oncosis and necrosis.

A

Oncosis is the spectrum of changes that occur in injured cells PRIOR to necrosis.

Necrosis are the morphological changes that occur after a cell has been dead for some time (12-24 hours)

39
Q

What are the 4 types of necrosis?

A
  1. Coagulative
  2. Liquefactive
  3. Caseous
  4. Fat necrosis
40
Q

What is the mechanistic difference between coagulative and liquefactive necrosis?

A

Desaturation of protein is the dominant mechanism of necrosis in coagulative necrosis.

Enzyme release and autolysis of proteins is the dominant mechanism in liquefactive necrosis.

41
Q

What type of tissues will undergo coagulative necrosis?

A

Solid organs with extensive connective tissue support

E.g Kidney, liver

42
Q

What type of cells are likely to undergo liquefactive necrosis?

A

Loose tissues with little connective tissue support.
E.g brain

Infected tissues - presence of many neutrophils

43
Q

What does coagulative necrosis look like?

A

“Ghost outline” of cells as the architecture is preserved.

Few neutrophils present.

44
Q

What does liquefactive necrosis look like?

A

Tissues are enzymatically digested so no outline visible.

Hole

45
Q

What disease is associated with casous necrosis?

A

Tuberculosis

46
Q

What does caseous necrosis look like?

A

Cottage cheese

Cellular debris visible but not in a uniform cellular outline.

47
Q

What does the term ‘gangrene’ mean?

A

Visible necrosis

48
Q

What does the term ‘infarct’ mean?

A

An area of necrotic tissue which is the result of loss of arterial blood supply.
- Area of ischaemic necrosis

49
Q

What is the difference between dry gangrene and wet gangrene?

A

Dry = necrosis modified by exposure to the air (coagulative necrosis)

Wet = necrosis modified by infection (liquefactive necrosis)

50
Q

What is gas gangrene?

A

Wet gangrene where the infection is with anaerobic bacteria that produce gas

51
Q

Why are some infarcts white?

A

If there is occlusion of an end artery in ‘solid organs’ with good stromal support then no haemorrhage will take place.
Coagulative necrosis.

52
Q

Why are some infarcts red?

A

In loose tissue with a dual blood supply, haemorrhage into the tissue.

53
Q

What are the effects of molecules leaking OUT of the injured cells?

A
  1. Local inflammation
  2. May have general toxic effects
  3. May appear in high concentrations in blood and aid diagnosis
54
Q

Which 3 key molecules can leak out of injured cells?

A
  1. Potassium
  2. Enzymes
  3. Myoglobin
55
Q

When does apoptosis occur physiologically?

A

Embryogenesis

56
Q

When does apoptosis occur pathologically?

A

Graft versus host disease - post-transplant

57
Q

Initiation of apoptosis results in the activation of which enzymes?

A

Caspases

  • control and mediate apoptosis
  • cause cleavage of DNA and proteins of the cytoskeleton
58
Q

How is the intrinsic apoptotic pathway initiated and carried out?

A
  • initiating signal from within the cell
  • p 53 protein is activated, causing outer mitochondrial membrane to become leaky
  • cytochrome c is released, causing activation of caspases
59
Q

What commonly triggers the intrinsic pathway of apoptosis?

A
  • irreparable DNA damage

- withdrawal of growth factors or hormones

60
Q

What are the 3 phases of apoptosis?

A
  1. Initiation (intrinsic + extrinsic)
  2. Execution
  3. Degradation & phagocytosis
61
Q

How is the extrinsic apoptotic pathway initiated and carried out?

A
  • Initiated by extracellular signals

- TNFa is one of the signals, binds to membrane ‘death receptor’ and activates caspases

62
Q

What usually triggers the extrinsic apoptotic pathway?

A

Cells that are in danger - e.g tumour cells, virus-infected cells

63
Q

How are apoptotic bodies phagocytosed?

A

Both pathways lead to cell shrinkage and budding into apoptotic bodies.

  • Apoptotic bodies express proteins on their surface
  • Recognised by phagocytes or neighbouring cells
64
Q

Contract the differences between apoptosis and oncosis.

A

Apoptosis:

  • Cell shrinkage and chromatin condensation
  • membrane integrity maintained
  • budding
  • lysosomal enzymes not involved
  • apoptotic bodies phagoctyosed
  • no inflammation
  • Often physiological

Oncosis:

  • Cell swelling
  • Blebbing and cell membrane disruption
  • Release of proteolytic enzymes
  • Inflammation
  • Pathological
65
Q

Where do abnormal cellular accumulations come from?

A

If a cell can’t metabolise something, it will remain within the cell.
Derive from -
cell’s own metabolism, extracellular space (e.g spilled blood), outer environment (e.g dust)

66
Q

What are the 5 main groups of intracellular accumulations?

A
  • Water and electrolytes
  • Lipids
  • Carbohydrates
  • Proteins
  • ‘Pigments’
67
Q

When does fluid accumulate in cells?

A

Low energy - hypoxia, as sodium pump will stop and sodium and water will flood into cell.

Indicates severe cellular distress

68
Q

Where in the body is fluid accumulation a particular problem?

A

Brain, enclosed in a skull so becomes compressed and blood supply compromised due to increased pressure.
= cerebral oedema

69
Q

When do lipids accumulate in cells and what are the common causes?

A
  • Steatosis (triglyceride accumulation)
  • Liver (major organ of fat metab)
  • excess cholesterol stored in vesicles

Causes: alcohol, diabetes mellitus, obesity, toxins.

70
Q

In what conditions do proteins accumulate in cells?

A
  • Alcoholic liver disease - Mallory’s hyaline (damaged keratin filaments)
  • a1-antitrypsin deficiency - incorrectly folded so cannot be packaged. Accumulates
71
Q

What are the 2 types of pathological calcification, how do they differ ?

A
  1. Dystrophic - occurs in area of dying tissue or damage. A local change or disturbance favours nucleation of hydroxyapatite crystals.
  2. Metastatic - body-wide disturbance.Hydroxyapatite crystals are deposited across the tissues when there is hypercalcaemia secondary to disturbances in calcium metabolism.
72
Q

What chromosomal component is responsible for cellular aging?

A

Telomeres at the ends of chromosomes.

Shorten as the cell replicated until it reaches a critical length when the cell can no longer divide.

73
Q

What molecule accumulates in jaundice?

A

Bilirubin

74
Q

Where would you expect to see fat necrosis?

A

Pancreatitis

Breast tissue

75
Q

What would be elevated in the blood during hepatitis?

A

Raised: CRP
ALT
AST (loss of hepatocyte integrity- leaking)
Bilirubin
Reduced albumin
Raised PT (reliant on factors 2,7,9,10 from liver)

76
Q

What would you expect to be raised/lowered in the blood of a patient with acute pancreatitis?

A

Serum amylase
Serum lipase
Hypocalcaemia possible - precipitation of salts in fat necrosis

77
Q

Which organs would you expect to see coagulative necrosis?

A

Liver

Kidney

78
Q

Infarcts in the lung are usually haemorrhagic. True or False?

A

True

79
Q

Apoptosis is seen in the liver in hepatitis. True or False?

A

True.

Virus-infected cells killed by extrinsic T- killer cell signals.

80
Q

Would lysosomal disruption be visible in reversible cell injury?

A

No

81
Q

Are nuclear changes visible during reversible injury?

A

No

82
Q

In anthracosis, where is the pigment located?

A

Alveolar macrophages

Pathological Processes (12 decks)

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