4. Cell injury Flashcards by Georgia Leggett

Lethal cell injury

Causes cell death

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Sublethal cell injury

produces injury not amounting to cell death

may be reversible or progress to cell death

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Cell stress

can lead to adaptation which may be reversible
inability to adapt will lead to cell injury and death
excess stress leads straight to damage

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Give an example of physiological cell stress

Exercise
Muscle cells increase in size as need more myofilaments to deal with increased work they have to do
Increases size of heart

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Give an example of pathological cell stress

High blood pressure
Causes muscles to adapt (hypertrophy)
Increases size of heart

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List 8 causes of cell injury

Oxygen deprivation
Chemical agents (Inc. drugs)
Infectious agents (Viruses, parasites etc)
Immunological reactions (Inc. Autoimmune)
Genetic defects
Nutritional imbalances
Physical agents
Aging

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Myocardial infarction

Muscle death due to ischaemia

Atheroma blocks artery

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Cellular response to injurious stimuli depends on

Type of injury
Duration
Severity

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Consequences of injurious stimuli depend on

Type of cell

The cell’s status e.g. dividing cells are more vulnerable than non-dividing

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Which 4 intracellular systems are particularly vulnerable to injury?

Cell membrane integrity- separates self from non-self
ATP generation- cells NEED energy
Protein synthesis- essential for growth, enzyme systems
Integrity of the genetic apparatus- DNA & RNA=problems with cell division and protein synthesis

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structural and biochemical components of a cell are integrally related, this means that

multiple secondary effects rapidly occur

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Atrophy

Shrinkage in size of cells (or organs) by loss of cell substance (Cell size and Number)

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5 Cellular adaptations to injury

Atrophy
Hypertrophy
Hyperplasia
Metaplasia
Dysplasia

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Example of atrophy

Dementia: Loss of neurones

Muscle atrophy secondary to denervation

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Hypertrophy

Increase in size of cells and consequently an increase in size of the organ

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Types of hypertrophy and examples of each

Physiological e.g. Pregnancy, Exercise

Pathological e.g. High BP

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What is hypertrophy caused by?

increased functional demand or specific hormonal stimulation

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Hyperplasia

An increase in number of cells in an organ

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Types of hyperplasia

Physiological

Pathological

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Physiological hyperplasia

either hormonal or compensatory

e.g. Proliferative Endometrium

Pathological hyperplasia

usually due to excessive hormonal or growth factor stimulation
e.g. Carcinoma

Metaplasia

A reversible change in which one adult cell type is replaced by another

types of metaplasia

Physiological

Pathological

Physiological metaplasia example

At puberty and during pregnancy cervix expands, opens canal, columnar exposed to acid pH causing columnar to become Squamous
If no pregnancy, cervix closes Squamous become Columnar

How is the Cervix lined?

internally by columnar | Externally by stratified squamous epithelium.

Pathological metaplasia example

Barrett’s Oesophagus | Acid reflux causes Squamous to become Columnar.

How is the oesophagus normally lined?

with stratified squamous epithelium

What happens if Barrets oesophagus is treated with a PPI, which inhibits acid production?

Columnar revert to being Squamous

Dysplasia

Precancerous cells which show the genetic and cytological features of malignancy but not invading the underlying tissue. E.g. High nuclear cytoplasmic ratio Increased mitosis

What are the light microscope changes associated with reversible injury?

Fatty change | Cellular swelling

Alcoholic fatty change

Excessive alcohol leads to fatty change in liver. | If stop drinking, fat goes away

Ballooning degeneration

Cells increase in size as cell membrane is damaged and fluid floods in, cells become swollen

Necrosis

Confluent (lots of cells next to each other) cell death associated with inflammation

What are the 4 light microscope changes associated with irreversible injury?

Coagulative necrosis Liquefactive necrosis Caseous necrosis Fat Necrosis

Coagulative necrosis

Cells dead, but still visible and recognisable

Example of coagulative necrosis

Myocardial infarct

Liquefactive necrosis

Cells die and disappear, with just liquid remaining

Example of Liquefactive necrosis

seen in brain in cerebral infarct

Caseous necrosis

Tissue maintains a cheese-like appearance | On cutting, is ‘creamy’, oozes out

Where is Caseous necrosis often seen?

Pulmonary TB

Fat necrosis

seen in inflammation of pancreas Lipase hydrolyses triglycerides to free fatty acids and glycerol Free fatty acids bind to calcium in ECF to form calcium fat salts which deposit in pancreas (chalky)

When is fat necrosis seen?

In acute pancreatitis

Apoptosis

Programmed cell death Single cell No inflammation Requires ATP

Characteristics of Necrosis

Mass cell death Inflammation Occurs when run out of ATP

Causes of apoptosis

Embryogenesis Deletion of auto-reactive T cells in the thymus Hormone-dependent physiological involution Cell deletion in proliferating populations A variety of mild injurious stimuli that cause irreparable DNA damage that triggers cell suicide pathways

What are the major differences between apoptosis & necrosis?

Apoptosis may be physiological Apoptosis is an active energy dependent process Apoptosis is not associated with inflammation

Necroptosis

Programmed cell death associated with inflammation

What could cause necroptosis?

Viral infection