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MD2001 > Responses to Cell and Tissue Injury > Flashcards

Responses to Cell and Tissue Injury Flashcards

1
Q

What are possible causes to sub-lethal injury ?

A

Hydropic change

Fatty change/steatosis

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2
Q

What happens if sub-lethal injury occurs over a long period of time ?

A 
Autophagy (cell shrinks in size because cell delivers cytoplasmic constituents to lysosomes) 
or Atrophy (wasting away because of degeneration of cells)
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3
Q

What are possible reasons for hydropic change or fatty change to occur ?

A

Failure of membrane functional integrity, blockage of metabolic pathways, interruption of protein synthesis.

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4
Q

In microscopy in liver cells, how does hydropic change look ?

A

Cells bigger and no longer pink since proteins (which may it pink) now diluted

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5
Q

In microscopy in liver cells, how does hydropic change look ?

A

Nucleus is no longer visible since fatty pushes nucleus to the side.

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6
Q

Which of lethal or sublethal injury is reversible ?

A

Sublethal injury

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7
Q

What is necrosis ? What are possible causes for it ? What is the consequence of it ?

A

Uncontrolled death of tissue following bioenergetic failure and loss of plasma membrane integrity

  • May be caused by ischaemia, metabolic or trauma
  • Results in inflammation since contents of the cell leaks (hence scarring and possible loss of function) and repair
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8
Q

What are the different kinds of necrosis ?

A

Coagulative necrosis - seen in most tissues. Involves coagulation of cellular proteins. Initially firm but later soft. Firm pale areas with ghost outlines in microscopy
Colliquative necrosis- seen in the brain. Dead area liquified (proteolysis dominates over coagulation) with formation of cystic spaces. Not much inflammation because cells are dead.
Caseous necrosis- seen in tuberculosis. Pale yellow semi-solid material.
Gangrenous necrosis- necrosis with putrefaction following vascular occlusions or certain infections. Black. May be wet or dry.
Fibrinoid necrosis- seen as a microscopic feature in arterioles in malignant hypertension.
Fat necrosis- May follow trauma and cause a mass, or follow pancreatitis and cause multiple white spots.

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9
Q

What are the main features of apoptosis ? What are the steps of it ?

A

Removal of cells discreetly without inflammatory response.
Takes out individual cells rather than groups of them
Requires energy
-Cell condenses, shrinks, loses water and breaks up. Fragments are still membrane bound until phagocytosed (e.g. by macrophage), so no inflammation.

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10
Q

What is the difference between Programmed Cell Death and Apoptosis ? Give examples of PCD.

A

PCD is about intent, Apoptosis is a morphological process. PCD usually through apoptosis but not always..

-lumen of tubes, menstrual cycle, death of neutrophils, T and killer cell responses, self destruction in autoimmune diseases, HIV and activated R cell death, prevention of mutations to prevent tumors

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11
Q

What are other types of PCD ?

A
  • Ferroptosis
  • Necroptosis
  • Pryoptosis (part apoptosis but then necrosis, associated with salmonelle infection)
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12
Q

In microscopy, how can you recognize a cell undergoing apoptosis ?

A

It is shrinking and its nucleus also shrinking.

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13
Q

Can apoptosis go wrong ? In which specific conditions?

A

1) Reduced apoptosis in: neoplasia, autoimmune disease, viral infection or cancer.
2) Increased apoptosis in: neurodegenerative disorders and HIV infection of T lymphocytes

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14
Q 
What are the main differences between necrosis and apoptosis in terms of: 
Induction
Extent 
Biochem events
Cell membrane integrity
Morphology
Inflammatory response
Fate of dead cells
A

Apoptosis :

  • Pathological or physiological
  • Single cells
  • Energy dependant fragmentation of DNA
  • Maintained
  • Cell shrinkage and fragmentation
  • None
  • Phagocytosed by neighbouring cells
Necrosis: 
Always pathological
Groups of cells
Abnormal ion homeostasis
Lost
Cell swelling and lysis
Usual
Phagocytosed by inflammatory cells
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15
Q

What occurs after injury ?

A

Either death, healing, or repair

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16
Q

What are the categories of cells used to describe their ability to be be replaced when lost ?

A

Labile and stable may be replaced

Permanent may not

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17
Q

What is healing ? Give examples.

A

Restitution with no or minimal residual defect. Abrasion to skin healing by first intention

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18
Q

What is repair ? Give examples.

A

When there is tissue lost, healing by second intention. Heart or lung damage result in a fibrous scar.

19
Q

Why can labile populations be replaced ? Give examples of labile populations.

A

Because constant proliferation and turnover.

Skin, blood, gut.

20
Q

Why can stable populations be replaced ? Give examples of stable populations.

A

Because although might have long time for turnover, able to regenerate if need be.
Liver, kidney.

21
Q

Why can’t permanent populations be replaced ? Give examples of permanent populations.

A

Because their ability to proliferate is close to 0.

Neurones, skeletal muscle.

22
Q

What is granulation tissue?

A

A tissue produced as part of a repair phenomenon.
Made of loops of new capillaries, proliferating myofibroblasts, possible inflammatory cells and collagen.
This tissue contacts to reduce wound size, which may result in stricture.
If a scar forms then it’s repair but not healing

23
Q

Which factors favour resolution ?

A

Minimal cell death and tissue damage
Occurrence in organ/tissue with regenerative capacity
Rapid destruction of causal agent
Rapid removal of fluid and debris by good local vascular drainage

24
Q

What is organisation ?

A

Repair of specialised tissued by formation of scar.

25
Q

What are the steps to organisation ?

A

1) Formation of granulation tissue, new blood vessels and macrophage conducting fibroblasts
2) Removal of dead cells by phagocyotsis
3) Wound contraction and scarring (may limit movement in joint)

26
Q

Which factors favour organisation ?

A

Maximal cell death and tissue damage
Exudate and debris cannot be removed or discharged
Large amounts of fibrin

27
Q

Which kind of post-injury does acute lobar pneumonia result in? Is there any exception to that?

A

Complete healing.
If S. Aureus infection then toxins cause necrosis of epithelial cells and enzymes of those dead cells may destroy collagen of alveolar cells.

28
Q

What is the diagnostic feature of healing by primary intention ?

A

Edges come together (opposite edges).

29
Q

What are the initial state of an injury healing by primary intention ?

A

Limited cell death but BM disrupted

30
Q

What is the diagnostic feature of healing by secondary intention ?

A

Wounds with separate edges (means we cannot minimise inflammation)

31
Q

What are the initial state of an injury healing by secondary intention ?

A

Extensive cell lost

32
Q

What are the major differences of healing by secondary intention compared to healing by primary intention ?

A
  • More haemorrhage
  • More necrotic tissue
  • More fibrin
  • Inflammation reaction more intense (so more macrophages, fibroblasts, new blood vessels, more collagen = BIG SCAR)
  • Much larger amount of granulation tissue
  • Contraction occurs to reduce size of the defect thanks to myofibroblasts (does not occur in healing by primary intention)
  • Skin regenerates from sides across granulation tissue rather than bottom up.
33
Q

What are the similarities between healing by primary and secondary intention ?

A

Large tissue defect which must be filled.

34
Q

When would healing by secondary intention be chosen over healing by primary intention ?

A

If there is a risk of foreign body or infective agent being left in the incisional space promoting inflammation and formation of an abscess.

35
Q

Which kind of tissue is bone (labile, stable or permanent ?)

A

Stable, able to proliferate if necessary

36
Q

What are the steps involved in bone healing ?

A

Fracture —> haemorrhage/necrosis/inflammation —> granulation tissue produced = new vessels + myofibroblasts + oedema + collagen (if acute inflammation lasts enough to turn into chronic inflammation) —> Osteoid also produced so this specialised granulation tissue morphs into bone matrix —> matrix becomes calcified —-> Remodelling of scar —> HEALING AND RESOLUTION (through repair + remodelling)

37
Q

What is the name given to the specialised granulation tissue in bone healing ?

A

Callus

38
Q

What are the steps to liver repair ?

A

Necrosis —> Regeneration —> Fibrous scarring —> Architectural disruption

39
Q

How does cirrhosis occur ?

A

Repeated damage (Scar tissue + regeneration) over time —> chronic inflammation —-> activated fibroblasts new vessel formation granulation tissue = Scar formation (fibrosis)

40
Q

How does wound strength alter over time ?

A

Suture removed at end of week 1- 10% initial strength (weak collagen)
Strength rapidly increase over following 4 weeks then rate of increase slows
3rd month- 70-80% (stronger collagen)
Full strength may never be recovered

41
Q

What are factors affecting wound healing ?

A

Systemic factors which include-

  • Age
  • Nutrition (affects protein and collagen synthesis)
  • Metabolic status (healing delayed in diabetics)
  • Circulatory status (adequate blood supply essential)
  • Hormones (glucocorticoids are anti-inflammatory but impair collagen synthesis)
  • Genetics

Local factors which include)

  • Infection
  • Foreign bodies (e.g sutures or glass)
  • Mechanical factors (early movement of wounds delays healing)
  • Size, location and type of wound (heals better in richly vascularised areas)
42
Q

What are examples of abnormal wound ?

A

-Deficient scar formation
Dehiscence (collagen not strong enough)
Ulceration

-Excess formation of repair components 
      Keloid scar (excessive fibroblast proliferation and collagen production resulting in huge scars)

-Formation of contractures (=”abnormal shortening of muscle tissue, rendering the muscle highly resistant to stretching”)
Exaggerated contraction
Deformity of the wound and surrounding tissues

43
Q

What are the pros of scars ?

A
  • Provides permanent patch

- Allows surrounding tissue to continue to function

44
Q

What are the cons of scars ?

A

-Cosmetic problems
-Functional problems
Site- E.g. Stricture (“abnormal narrowing of a body passage”)
Size- E.g. Healed myocardial infarct

MD2001 (35 decks)

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