Responses to Cell and Tissue Injury Flashcards by Morgan Eriksson

What are the major causes of disease on a cellular level?

Change in homeostasis caused by;

Retaining more water within the cell- oncosis

Accumulating of fat- steatosis

Autophagy

Atrophy

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What is autophagy?

Cells eating itself up

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What is atrophy?

Decrease in cell size through autophagy

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What are examples of sublethal injury?

Energy failure

Mechanical disruption

Damage to cell membrane caused by free radicals

Blockage of metabolic pathways

Failure of membrane integrity

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What are the different types of nature of the injury?

Acute vs chronic

Mild versus severe

Cell type affected

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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 does necrosis induce?

Inflammation and repair.

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What can cause necrosis?

Ischaemia, metabolic and trauma.

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What are the different categories of necrosis?

Coagulative, colliquative, caseous, gangrene, fibrinoid and fat.

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What is coagulative necrosis?

Can happen in most tissues. Appears as a firm pale area.

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Where is colliquative necrosis seen?

Seen in the brain.

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What is observable in colliquative necrosis?

The dead area is liquified.

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Which disease is associated with caseous necrosis?

Tuberculosis

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What is observable with caseous necrosis?

There is a pale yellow semi-solid material.

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What is putrefaction?

The process of decay or rotting in a body.

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Which necrosis involves putrefaction?

Gangrene necrosis.

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What does gangrene necrosis follow?

Vascular occlusion or certain infections.

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What colour is observable with gangrene necrosis?

Black

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What is fibrinoid necrosis?

A microscopic feature in arterioles in malignant hypertension.

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What may fat necrosis follow?

Trauma or pancreatitis.

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What may be seen with fat necrosis after pancreatitis?

Multiple white spots.

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What may be seen with fat necrosis after trauma?

A mass.

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Define apoptosis.

The death of cells which occurs as a normal and controlled part of an organism’s development.

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What causes reduced apoptosis?

Neoplasia, autoimmune disease and virus infection

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What causes increased apoptosis?

Neurodegenerative disorders and HIV infection of T lymphocytes.

What does apoptosis effect?

Single cells

What does necrosis effect?

Cell groups

What are the biochemical events of apoptosis?

Energy-dependent fragmentation of DNA

What are the biochemical events of necrosis?

Abnormal ion homeostasis

Is the cell membrane integrity maintained in apoptosis?

Yes

Is the cell membrane integrity maintained in necrosis?

What is the morphology in apoptosis?

Cell shrinkage and fragmentation

What is the morphology in necrosis?

Cell swelling and lysis

What is the fate of dead cells with apoptosis?

Phagocytosed by neighbouring cells

What is the fate of dead cells in necrosis?

Phagocytosed by inflammatory response

What is the commonest type of necrosis?

Coagulative necrosis

What is involved in coagulative necrosis?

Involves coagulation of cellular proteins

What is involved in colliquative necrosis

Liquefaction with formation of cystic spaces

What dominates over coagulation?

Proteolysis

Define proteolysis

The breakdown of proteins or peptides into amino acids by the action of enzymes

What is gas gangrene due to?

C perfringens

What is fibrinoid necrosis most commonly associated with?

Malignant hypertension

What is pyroptosis?

A highly inflammatory form of programmed cell death

When does pyroptosis occur most?

Infection with intracellular pathogens

What stages of response does pyroptosis fall into?

Part of apoptosis but then necrosis

What infection is pyroptosis associated with?

Salmonella infection

Define healing.

Restitution with no, or minimal, residual defect.

What is repair?

Is necessary when there is tissue loss: healing by second intention.

Which tissues can heal?

Blood, skin and gut.

Which tissues can repair?

Liver and kidney.

What is the function of granulation tissue?

Actively contracts to reduce wound size which may result in a stricture later.

What needs to be rapid in order to favour resolution?

Rapid destruction of casual agent and rapid removal of fluid/debris by good local vascular drainage.

Where should injury happen to favour resolution?

In an organ or tissue with regenerative capacity e.g. liver.

What is a factor that favours resolution of an injury?

Minimal cell death and tissue damage.

Define organisation.

Repair of specialised tissue by formation of a scar.

What is formed during organisation?

Granulation tissue.

What is removed during organisation?

Dead tissue by phagocytosis.

What happens to the wound during organisation?

Wound contraction and scarring

What substance favours organisation?

Large amounts of fibrin

What is fibrin?

An insoluble protein formed from fibrinogen during the clotting of blood

What event favours organisation?

Substantial necrosis.

What is granulation tissue formed of?

Loops of capillaries, myofibroblasts, collagen and inflammatory cells.

What organises granulation tissue?

Deposition of collagen and contraction?

What moves towards a clot in healing by first intention?

Neutrophils.

How much cell death is there in healing by first intention?

Limited cell death

What happens to the epidermis in healing by first intention?

It thickens at its cut edges

What do epidermal cells do in healing by first intention?

They migrate along cut margins of dermis.

What do epithelial cells do in healing by first intention?

They fuse in the midline beneath the surface of the scab.

By day 3 what has happened in healing by first intention?

Neutrophils largely replaced by macrophages.

What has happened by day 5 in healing by first intention?

Granulation tissue invades incision space

What happens before the epidermis has recovered normal thickness in healing by first intention?

The collagen fibres bridge the incision.

What is there an accumulation and proliferation of during the second week of healing by first intention?

Accumulation of collagen and proliferation of fibroblasts

What has happened by the end of the 1st month in healing by first intention?

Scar consists of cellular connective tissue. (Tensile strength now increases).

What is healing by first intention?

Wound with opposed edges.

What is healing by second intention?

Wounds with separated intention

Is there extensive cell loss in healing by second intention?

Yes

What is the common denominator in healing by second intention?

A large tissue defect that must be filled

What plays an important role in reducing the size of defect in healing by second intention?

Wound contraction

What is there more of in healing by second intention?

More fibrin and more necrotic tissue

What differentiates between first and secondary healing?

Wound contraction

What has been contraction been ascribed to?

The presence of myofibroblasts.

What are the stages of bone healing?

Repair, remodelling and resolution.

What happens when the liver is damaged?

Necrosis, regeneration, fibrous scarring and architectural disruption.

What are the systemic factors that influence wound healing?

Age, nutrition, metabolic status, circulatory status and hormones.

Why does nutrition affect wound healing?

Affects protein and collagen synthesis

How can hormones affect wound healing?

Glucocorticoids anti-inflammatory but impair collagen synthesis

What local factors may influence wound healing?

Infection, mechanical factors, foreign bodies, size, location and type of wound

What are the two forms of deficient scar formation?

Dehiscence and ulceration

What is a keloid scar?

A tough heaped-up scar that rises above the rest of the skin.

Define oncosis.

Cellular swelling

Define steatosis.

Abnormal condition of fat, any change to pH or other conditions causes a different way of producing fat

What is autophagy?

A process in which lysosomes decompose damaged organelles to reuse their organic monomers.

Define atrophy.

To waste away

What is an acute injury?

An injury with sudden onset and short duration.

What is a chronic injury?

An injury that develops over a long period of time.

What is an hydropic change?

Damage leads to water entering cells to be sequestered into vacuoles.

What defines a mild injury?

Regeneration and no scarring.

What defines a lethal injury?

Irreversible injury that causes cell death

What is a severe injury?

Fibrinous exudate

What is ischaemia?

Lack of blood to a part of the body

What are some examples of apoptosis?

Embryology, lumen of tubes. HIV AIDS-activated T cell death

What cells can be replaced if lost?

Labile and stable

What are the types of permanent tissues?

Neurones and skeletal muscle