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Pathology > Necrosis > Flashcards

Necrosis Flashcards

1
Q

What are the causes of cell injury?

A
  • hypoxia due to ischaemic, inadequate oxygenation and anaemia
  • living irritants like bacteria, fungus, virus and parasites
  • physical irritant
  • chemical irritant
  • immunological reactions
  • nutritional deficiencies
  • genetic and enzymatic abnormalities
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2
Q

What causes necrosis AND inflammation?

A
  • chemical irritant
  • physical irritant
  • living irritant
  • immunological reactions
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3
Q

What is the definition of necrosis?

A

local death of cells ir tissues in the living body

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4
Q

What are the causes and pathogenesis of necrosis?

A

same as reversible cell injury

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5
Q

What is the gross picture of necrosis?

A

necrotic tissue appears opaque, white or yellow area surrounded by red zone of acute inflammation even if the cause does not cause inflammation

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6
Q

What is the microscopic picture of necrosis?

A

immediately after necrosis, dead cells appear more or less normal then followed by autolytic (post-necrotic) changes that take place due to the effect of lysosomal enzymes (after 6 hours)

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7
Q

What are the autolytic changes that take place during necrosis?

A
  • nuclear changes
  • cytoplasmic changes
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8
Q

What are the nuclear changes that take place in necrosis?

A
  • pyknosis
  • karyorrehxis
  • karyolysis
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9
Q

What is pyknosis?

A

nucleus becomes small, irregular and deeply stained

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10
Q

What is karyorrehxis?

A

fragmentation of nucleus into small pieces

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11
Q

What is karyolysis?

A

dissolution of nuclear fragments

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12
Q

What are the cytoplasmic changes that take placeduring necrosis?

A
  • the cells swell (except nucleus) (cytomegaly), the cytoplasm becomes homogenous and the cells lose their cell membrane
  • necrotic cells now appear as homogenous structureless area
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13
Q

What are the types of necrosis?

A
  • coagulative necrosis
  • liquefactive necrosis
  • caseous necrosis
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14
Q

What happens in coagulative necrosis?

A
  • necrotic tissues appear firm and dry
  • caused by cut of blood supply
  • at first, there is loss of cellular details and preservation of architecture for some time
  • later on, there is loss of both
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15
Q

What happens in liquefactive necrosis?

A
  • necrotic tissue appears as liquid
  • not found in all tissues
  • in case of CNS infarction, the cause of liquefaction is the high lipid and fluid content
  • in case of pyogenic abscess, the cause of liquefaction is the lysosomal enzymes released from dead polymorphs (pus cells)
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16
Q

What happens in caseous necrosis?

A
  • begins as coagulative necrosis followed by slow partial liquefaction
  • necrotic area appears semi-solid semi-fluid like casein of milk
  • commonly seen in tuberculosis and syphilis
  • the cause of necrosis is antigen-antibody reaction
  • there is loss of cellular details followed by loss of architecture
17
Q

What are the types of fat necrosis?

A
  • enzymatic fat necrosis
  • traumatic fat necrosis
18
Q

How does enzymatic fat necrosis occur and when does it occur?

A
  • occurs in acute haemorrhagic liquetising pancreatitis
  • lipase enzyme escapes from ruptured pancreatic ducts and acts on fat in abdominal cavity, splitting it into fatty acids and glycerol
  • glycerol is absorbed and fatty acids combine with calcium from blood plasma and become deposited as opaque white patches
  • a person can die from hypocalcaemia
  • affected fat cells are swollen and surrounded by foreign body giant cell reaction and fibrosis
19
Q

How does traumatic fat necrosis occur and when does it occur?

A
  • occurs as a result of trauma to fatty areas as the female breast or any tissue that has fat and trauma
  • self digestion of fat splits it into fatty acid and glycerol
  • glycerol is absorbed and fatty acids combine with calcium and become deposited and induces fibrosed hard mass
  • malignant tumours occur in dry and hard mass in breast
  • affected fat calls are swollen and surrounded by foreign body giant cell reaction and fibrosis
20
Q

What is the definition of apoptosis?

A

a special type of death affecting a single cell or a small group of cells and is sometimes referred to as cell suicide

21
Q

What are the morphological changes that take place during apoptosis?

A
  • shrinkage of nucleus
  • condensation and fragmentation of chromatin
  • chromatin fragments are enclosed in parts of cell membrane to form apoptotic bodies and are phagocytosed by macrophages or adjacent phagocytic cells
22
Q

Why does apoptosis occur?

A
  • normal cell turn over (all tissues except brain CNS)
  • programmed cell death during embryonic development
  • endocrine dependent tissue involution: menstrual cycle (endometrial involution)
  • in some pathologic conditions
23
Q

What are the pathologic conditions that lead to apoptosis?

A
  • cell death by cytotoxic lymphocytes (no inflammation)
  • liver cells in viral hepatitis
  • radiation cell injury
  • pathological atrophy
24
Q

What are the types of pathological calcification?

A
  • dystrophic calcification
  • metastatic calcification
25
Q

What is dystrophic calcification?

A

deposition of calcium salts in dead and degenerating tissues and it is more common than metastatic calcification

26
Q

What causes dystrophic calcification?

A
  • local alkalinity of dead tissue and increased phosphatase activity
  • occurs with normal calcium level
27
Q

What are examples of dystrophic calcification?

A

areas of…
- necrosis
- fibrosis
- hyalinosis
- thrombosis
- tuberculosis
(anything that ends with -osis)

28
Q

What is metastatic calcification?

A

deposition of calcium salts in living tissues and is less common than dystrophic calcification

29
Q

What causes metastatic calcification?

A
  • high blood calcium level due to increased calcium intake or hypervitaminosis D
  • increased calcium mobilisation from bone as in hyperparathyroidism and bone tumours
  • relative alkalinity of affected tissue
30
Q

What are the sites of metastatic calcification and why?

A

stomach, kidney and lungs because these organs secrete acidic secretions and their wall is always relatively alkaline

Pathology (5 decks)

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