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2.1 Necrosis Flashcards

1
Q

Necrosis is?

A

necrosis is the death of cells within the living body

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2
Q

Cellular events in necrosis:

A
  • Pyknosis
  • karyorrhexis
  • karyolysis​
  • cytoplasm
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3
Q

pyknosis:

A

normal nuclear structure is replaced by a very dense, heavily staining, smaller angular mass of chromatin

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4
Q

karyorrhexis:

A

nucleus has broken up into several dense pieces

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5
Q

karyon =

A

nucleus

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6
Q

rhexis =

A

breaking up

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7
Q

karyolysis:

A

nuclear staining with haematoxylin becomes faint and only the ghost outline​ of the nucleus remains

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8
Q

cytoplasm sometimes stains?

A

brighter pink ( more eosinophilic​)
- pH drops and becomes more acidoc

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9
Q

Describe whats ​happening in pyknosis:

A
  • clumping of chromatin
  • general swelling of cell / ER due to water

Has a smaller nucleus and no nucleolus

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10
Q

Describe what’s​ happening in karyolysis:

A
  • dissolution of nuclear structure
  • rupture of cell membrane
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11
Q

Pyknosis: Which one is normal and infected? How can you tell?

A

A: infected: surrounded by darker pink cytoplasm
B: normal

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12
Q

Karyorrhexis: What are these cells? How can you tell?

A

Necrotic cells: dark blue/ black = fragmented nucleus material

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13
Q

3 main causes of necrosis?

A
  1. loss of blood supply - tissues need blood to supply to remain alive
  2. living agents - bacteria, virus, fungi, parasites
  3. Non-living​ agents - chemicals or physical injuries
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14
Q

loss of blood supply causes:

A
  • hypoxia
  • ischemia
  • infarction
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15
Q

hypoxia:

A

reduced oxygen supply

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16
Q

ischemia​:

A

loss of blood supply
- complete loss

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17
Q

infarction:

A

sudden loss of blood supply to a portion of a tissue or organ

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18
Q

The consequences​​ of ischaemia depend on:

A
  • Type of cell: essential functioning cells (parenchyma) much more susceptible than the connective tissue supportive cells (stroma)
  • the metabolic activity of the tissue: very active organs are more susceptible ex: heart, liver, lungs
  • whether or not there is a good or potential collateral blood supply ex: kidney​ (important) vs lung not much difference
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19
Q

Tissue ischemia​ occurs in 3 different ways:

A
  1. compression of the blood vessels from outside
  2. narrowing of the vessel lumen due to mural (wall) thickening
  3. blockage of the vessel lumen
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20
Q

ischemia in tissues: intestinal torsion - compression of the blood vessels

A
  • venous outflow impeded
  • organ swells due to congestion
  • swelling impedes the arterial flow and arterial flow stops
  • tissue undergoes ischaemic necrosis
  • intestinal blood barrier compromised​
  • bacterial toxins absorbed - death or intestine friable: prone to rupture with peritonitis
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21
Q

ischemia in tissues: narrowing of the vessel lumen - Arteriosclerosis

A
  • may occur in hypertension
  • rare in animals ( occasionally dogs with hypothyroidism or diabetes)
  • arteries harden
22
Q

ischemia in tissues: blockage of the lumen

A
  • important in animals: thrombosis and embolism
23
Q

Physical agents causing necrosis:

A
  • burns
  • cold/frostbite
  • x-rays
  • pressure
  • pinching or crushing tissue
24
Q

chemical agents causing necrosis:

A

directly caustic or corrosive in action or exert their effect when absorbed​ and metabolized to a more toxic substance

25
Living agents that cause​ necrosis: Black disease
infectious necrotic hepatitis - clostridium novyi type B spores germinate in anaerobic environment created by the ​migration of liver fluke
26
Black disease histology: 3 zones
- Normal liver - Zone of inflammation (arrows) - central​ zone of necrosis
27
Gross and histological features of necrotic tissues:
- color change: dead tissues tend to be paler due to loss of circulation - consistency (texture): will vary according to the type of agent responsible, the tissue in which it is acting **appearance may give clue to agent responsible, and type of necrosis based on their gross appeaernce
28
What are the 3 main gross types/descriptions
1. coagulative necrosis - remains firm 2. liquefactive necrosis - becomes liquid 3. caseous necrosis - looks like cottage cheese Others - fat necrosis - hard soap like appearance of affected body fat - Gangrene - mostly a post -necrotic changhe
29
What necrosis gross appearnace​ is this?
Coagulative: firmer and drier on the cut surface but will still resemble​ in outline the adjacent viable tissue
30
Describe coagulative microscopic necrosis:
- architecture of the tissue is preserved - cells may appear somewhat larger and their outline may be lost - cytoplasm appears structureless and homogenous - important nuclear changes
31
What causes coagulative necrosis?
bacteria which produce toxins (clostridiuam spp) infarction, and some foci of viral replication ex: herpes virus
32
2 types of liquefactive necrosis:
1. malacia - CNS 2. abscesses - anywhere in the
33
liquefactive necrosis: abscesses
- pyogenis (pus producing) - bacteria causes necrosis and attract vast numbers of neutrophils which they alos kill
34
dying neutrophils release?
proteolytic enzymes - which digest necrotic tissue - kill further tissue cells - kill other incoming neutrophils
35
Pus =
dead dying neutrophils, dead tissues and organisms
36
Caseous necrosis gross appearance:
- cheese like necrosis - white to yellowish color - dry and crumbling to cottage cheese ** really a mix of coagulation and liquefactive necrosis
37
Caseous is caused by?
specific organisms ex: mycobacteria
38
Caseous necrosis: mycobacteria tuberculosis
- Microscopic: complete loss of architecture - purplish necrotic material due to nuclear and cytoplasmic components that stain with H&E - large portion composed of macrophages
39
Mycobacteria have a high?
high lipid cell wall which resists digestion and allows replication​ within macrophage and evasion of phagolysis - organisms burst the macrophage and engulf by other macrophages
40
Sequelae to necrosis:
- surface necrosis can be shed basement membrane intact: epithelium regenerates = erosion - basement membrane breached, host inflammatory response​ --> tissue repair by fibrosis = ulceration
41
small foci replaced by fibrous tissue =
scarring
42
larger foci are replaced by fibrous tissue =
sequestrum
43
Fat necrosis: gross appearance​
- areas of focal opacity - very hard consistancy
44
Fat necrosis: enzymatic
release of pancreatic enzymes lipase from a damaged pancreas into the adjacent mesenteric fat ex: pancreatitis
45
fat necrosis: traumatic
In subcutaneous tissue following trauma to the area - common in brisket of animals due to prolonged pressure
46
Fat necrosis: diet related
rarley in cats associated with diets lacking antioxidants ex: vitamin E
47
Gangrene:
post-necrotic change (ex: putrefaction of tissues
48
wet gangrene:
primary: agent which initially kills the tissue, further putrefies secondary: dead tissue being invaded by organisms which putrefy​ it
49
dry gangrene
type of mummification - occurs on the extremities - air passing over the extremity removes the fluid content of the dead tissue - appears lethery
50
Can be a feature of granulomatous disease
Caseous necrosis: It is a prominent feature of granulomatous tuberculosis in cattle, the necrosis being composed of dead macrophages and organisms

Pathology (7 decks)

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