Responses to Cell and Tissue Injury Flashcards by Morgan Eriksson

What is sublethal injury?

Reversible cell injury

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What are the causes of sublethal injury?

1- Oncosis: hydropic change

2- Steatosis: fatty change

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What can sublethal injury lead to over a longer amount of time

1- Autophagy

2- Atrophy

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What is autophagy?

1- Intracellular degradation system
2- ‘Self-eating’
3- If the contents of the cell are too much in comparison the the energy provided, cell down-sizes

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What is atrophy?

Wasting away of cells or tissue

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What is necrosis?

The death of tissues following bioenergetic failure and loss of plasma membrane integrity

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What kind of response can necrosis evoke?

Inflammatory response

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What are the six different types of necrosis?

1- Coagulative
2- Colliquative
3- Caseous
4- Gangrenous
5- Fibrinoid
6- Fat necrosis

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What are the three main causes of necrosis?

1- Ischaemia
2- Metabolic disorders
3- Trauma

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What is coagulative necrosis?

1- Most common, can happen in most tissues
2- Involves coagulation of cellular proteins
3- Firm pale area with ghost outlines on microscopy, appearance develops over time
4- Initially firm but later soft
5- Leads to an inflammatory response

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What is colliquative necrosis?

1- Liquefaction with formation of cystic spaces

2- Proteolysis dominates over coagulation

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What is caseous necrosis?

1- Characteristic of TB

2- Soft and white cheese-like dead tissue

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What is gangrenous necrosis?

1- Necrosis with putrefaction
2- Wet and dry forms
3- Gas gangrene due to C perfringens

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What is fibrinoid necrosis?

1- Histological observation/phenomenon

2- Most commonly associated with malignant hypertension

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What is fat necrosis?

1- As a result of trauma
2- May cause a mass
3- May come after or due to pancreatitis and appear as multiple white spots

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What is lethal injury?

1- Cell’s complete loss of ability to release sodium or water due to loss of plasma membrane integrity, leading to cell bursting
2- Irreversible, permanent death

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What is apoptosis?

1- Programmed cell death
2- Removes a cell discreetly
3- Removes individual cells rather than groups of tissues
4- Preserve function as best as possible

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What are indications of reduced apoptosis?

1- Neoplasia
2- Autoimmune disease
3- Virus infection

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What are indications of increased apoptosis?

1- Neurodegenerative disorders

2- HIV infection of T lymphocytes

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Compare the induction of apoptosis and necrosis.

1- Apoptosis: physiological or pathological

2- Necrosis: pathological

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Compare the extent of the effect of apoptosis and necrosis.

1- Apoptosis: single cells

2- Necrosis: cell groups/tissue

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Compare the biological events of apoptosis and necrosis.

1- Apoptosis: energy-dependent fragmentation of DNA

2- Necrosis: abnormal ion homeostasis

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Compare the cell membrane integrity during apoptosis and necrosis.

1- Apoptosis: maintained

2- Necrosis: lost

Compare cell morphology in apoptosis and necrosis.

1- Apoptosis: shrinkage and fragmentation

2- Necrosis: swelling and lysis

Compare the inflammatory response in apoptosis and necrosis.

1- Apoptisis: none/never | 2- Necrosis: normally present/usual

Compare the fate of dead cells in apoptosis and necrosis.

1- Apoptosis: phagocytosed by neighbouring cells | 2- Necrosis: phagocytosed by inflammatory cells

What is pyroptosis?

1- Part apoptosis but then necrosis | 2- Associated with salmonella infection

What is pyroptosis usually associated with?

Salmonella infection

What three options may happen after injury?

1- Death 2- Healing 3- Repair

In regards to cell repair, what are the three types of cells?

1- Labile 2- Stable 3- Permanent

What is labile tissue?

Tissue which is able to carry out a lot of cell proliferation, leading to quick cell regeneration

Give three examples of labile tissue.

1- Blood 2- Skin 3- Gut

What is stable tissue?

Cells which do not carry out constant proliferation, but rather remain at rest and only regenerate when needed.

Give two examples of stable tissue.

1- Liver | 2- Kidney

What is permanent tissue?

Tissue which does not regenerate under any circumstances.

Give two examples of permanent tissue.

1- Neurons | 2- Skeletal muscle

What factors favour resolution?

1- Minimal cell death and tissue damage 2- Occurence in tissue or organ with regenerative capacity 3- Rapid destruction of causal agent 4- Rapid removal of fluid and debris by good local vascular drainage

What is organisation?

Repair of specialised tissue by formation of a scar

What three steps are involved in organisation?

- Formation of granulation tissues 2- Removal of dead tissue by phagocytosis 3- Wound contraction and scarring

What factors favour organisation?

1- Large amounts of fibrin 2- Substantial necrosis 3- Exudate and debris cannot be removed or discharged

Describe the structure of granulation tissues.

1- An intermediate substance 2- Contains loops of capillaries, myofibroblasts, collagen and inflammatory cells 3- Organised by the deposition of collagen and contraction

What is healing by first intention?

1- Healing of a clean wound without cell death or tissue loss 2- Basement membrane may be disrupted

What are the steps of healing by first intention?

1- Incisional space fills with blood 2- Scab forms 3- Neutrophils move towards clot 4- Epidermis thickens at its cut edges 5- Epidermal cells migrate along cut lines of dermis 6- Epithelial cells fuse in the midline beneath the surface scab 7- On day 3, neutrophils are largely replaced by macrophages 8- On day 5, granulation tissue invades incision space 9- Collagen fibres bridge the incision 10- Epidermis recovers to normal thickness

What happens on day three of healing by first intention?

Neutrophils are replaced by macrophages

What happens on day five of healing by first intention?

Granulation tissue invades incision space

What happens during the second week of healing by first intention?

1- Proliferation of fibroblasts 2- Collagen accumulation 3- Leucocytes infiltrate, oedema reduced 4- Vascularity virtually disappears

What happens after the first month of healing by first intention?

1- Scar consists of cellular connective tissue | 2- Tensile strength increased

What is healing by second intention?

1- Healing of wounds with separate edges 2- Extensive cell loss 3- Usually present when there is a large tissue defect 4- Much larger amounts of granulation tissue

What factors favour healing by second intention?

1- Large amounts of fibrin 2- A lot of necrotic tissue 3- If the inflammatory reaction was more intense

With regards to healing by second intention, what plays an important role in reducing the size of defect?

Wound contraction

What is wound contraction?

When a normal healing process leads to physical deformity and functional limitations.

What are the three steps of bone healing?

1- Repair 2- Remodelling 3- Resolution

What systemic factors influence wound healing?

``` 1- Age 2- Nutrition 3- Metabolic status e.g. diabetes 4- Circulatory status 5- Hormones ```

What local factors influence wound healing?

1- Infection 2- Mechanical factors (e.g. early movement of wounds delay healing) 3- Foreign bodies 4- Size, location and type of wound

What three things may happen which exhibit abnormal wound repair?

1- Deficient scar formation 2- Excessive formation of repair components 3- Formation of contractures

What are two examples of deficient scar formation?

1- Dehiscence (wound rupture) | 2- Ulceration

What is a keloid scar?

1- A type of scar which stands proud of the skin | 2- Due to excessive fibroblast proliferation and overproduction of collagen