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PVS > Pathology: Cell Injury > Flashcards

Pathology: Cell Injury Flashcards

1
Q

What can cause cell injury?

A 
Hypoxia
Mechanical trauma
Electricity/radiation
Chemicals/drugs
Pathogens
Immunolgic reactions
Genetic and nutritional deficiencies
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2
Q

What causes hypoxia to cells?

A

Reduced blood. flow (Ischaemia)
Inadequate oxygenation of the blood (CR failure)
Decreased oxygen carrying capacity of the blood (Anaemia, carbon monoxide poisoning, hypovolaemia)

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3
Q

Is degeneration reversible?

A

Yes

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4
Q

What happens to a cell when the ATP is depleted (degeneration)?

A

The cell swells due to failure of the energy dependent ion pumps in the plasma membrane leading to a a loss of K+ and gain of Ca, Na and water

Steatosis (fatty change) where there is abnormal accumulations of neutral lipids (triglycerides) within the parenchymal cells - often seen in the liver

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5
Q

What causes steatosis (fatty change)?

A

Excessive production/mobilisation of lipids: Diabetes mellitus (depleted carb stores lead to a breakdown of fats and protein - increase in FFA’s)

Defective metabolism and export of lipids

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6
Q

Is necrosis reversible?

A

No

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7
Q

When biochemical changes occur in the cell is it reversible?

A

No

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8
Q

What happens when a cell necroses?

A

Denaturation of intracellular proteins and enzymatic digestion of the lethally injured cell (enzymes one from the lysosomes of the dying cells and also from leukocytes)

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9
Q

When a cell necroses and leaks cellular contents what can happen?

A

Inflammation

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10
Q

How can cell necrosis be detected in the blood?

A

Leaked enzymes and proteins can be detected in the blood (Creatinine kinase, alkaline phosphatase…)

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11
Q

What are the biochemical/ultrastuctural changes that occur during necrosis?

A

Depletion of ATP
Mitochondrial damage
Influx of calcium and loss of calcium homeostasis
Accumulation of oxygen derived free radicals
Defects in membrane permeability
Damage to DNA and proteins

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12
Q

What causes depletion of ATP in necrosis?

A

Reduced supply of oxygen, mitochondrial damage, toxins

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13
Q

What causes mitochondrial damage in necrosis?

A

Hypoxia and toxins

It causes a depletion of ATP and a release of pro-apoptotic proteins (cytochrome C)

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14
Q

What causes the influx of calcium in necrosis?

A

Ischaemia and toxins
It causes an increase in mitochondrial permeability (causing mitochondrial damage) and release of cellular enzymes (Phospholipases, proteases, endonuclease ATPases)

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15
Q

Where is most of the calcium in the cell?

A

Low concentrations in the cytoplasm and most intracellular calcium is sequestered in the mitochondria and the endoplasmic reticulum

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16
Q

What causes accumulation of oxygen-derived free radicals?

A

Inflammation, radiation, chemicals

17
Q

What are reactive oxygen species?

A

ROS are produced normally in cells doing mitochondrial respiration and energy generation but they are degraded and removed by the cellular defences (antioxidant and enzymes)

18
Q

What are free radicals?

A

Chemicals that have single unpaired electron in an outer orbit, energy created by this unstable configuration is released through reactions with adjacent molecules

19
Q

What causes the defects in membrane permeability during necrosis?

A

Ischaemia, toxins, viruses, physical/chemical agents

It causes mitochondrial damage, ATP depletion, apoptosis

20
Q

What are the cytoplasmic and nuclear changes that occur in necrosis?

A

Cytoplasmic changes: Increases eosinophilia in HE and cytoplasmic vacuolation

Nuclear changes: Karyolysis/ Pyknosis /Karyorrhexis

21
Q

What is karyolysis?

A

Nuclear fading

22
Q

What is pyknosis?

A

Nuclear shrinkage

23
Q

What is karyorrhexis?

A

Nuclear fragmentation

24
Q

What is coagulative necrosis?

A

The architecture of the dead tissues is preserved as injury denatures the structural proteins but also enzymes so blocks proteolysis
Has a firm texture eg. Infarct

25
Q

What is an infarct?

A

A localised area of coagulative necrosis caused by ischaemia due to vascular obstruction

26
Q

What is liquefactive necrosis?

A

A liquid viscous mass caused by enzymatically digested dead tissue (architecture is not preserved)
Eg. Pus, malacia
Common in microbial infection as the leukocytes liberate the enzymes from cells

27
Q

What is Malacia?

A

Liquefactive necrosis in the CNS

28
Q

What is gangrenous necrosis?

A

A vacation of coagulative necrosis, usually an extremity that has let its blood supply.
Three types: dry, moist and gas

29
Q

What is caseous necrosis?

A

Conversion of cells into a cheese-like mass of necrotic tissue. Typically more chronic than coagulation necrosis.
Seen in TB

30
Q

What is fat necrosis?

A

Focal areas of fat destruction, the fat appears white, firm and chalky like flecks of soap
Typically as a cause of pancreatic releases

31
Q

What is the process of fat saponification?

A

Triglyceride esters are covered to fatty acids by lipase and then are saponificated by calcium

32
Q

Do the cell membranes become permeable in apoptosis?

A

No they remain intact

33
Q

Does apoptosis cause inflammation?

A

No

34
Q

What is apoptosis?

A

Programmed cell death

35
Q

How do cells apoptose?

A

The chromatin condenses and the cell breaks up into apoptotic bodies with inactivity plasma membranes and the apoptotic bodies are removed by phagocytes (usually macrophages)

36
Q

What causes apoptosis?

A

Physiologic: Programed such as elimination of self reactive lymphocytes
Pathologic: DNA damage, accumulation ofmisfolded proteins, viral infections, atrophy in the organs

37
Q

What are the biochemical mechanisms of apoptosis?

A

Activation of capsases (they exist as pro-enzymes and must undergo enzymatic cleavage to become active)

DNA breakdown by endonuclease that are activated by capsases
Protein breakdown by capsases

Membrane alterations to promote phagocytosis

38
Q

What is the intrinsic mechanism of apoptosis?

A

Increased mitochondrial permeability with release of pro apoptotic molecules (eg. Cytochrome C)

PVS (43 decks)

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