Cell Injury and Death

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Questions and Answers

What characterizes necrosis?

Cell shrinkage and a reduction in intracellular protein synthesis

Self-digestion of cells leading to tissue repair

Programmed cell death under normal physiological conditions

Cell swelling, protein denaturation, and organellar breakdown (correct)

Which mechanism of cell injury is associated with inadequate oxygenation of blood?

Genetic defects

Trauma from physical agents

Hypoxia specifically (correct)

Chemical alteration of membrane permeability

In which of the following scenarios does apoptosis occur?

During an anaphylactic shock reaction

Following exposure to severe physical trauma

As a natural part of physiological processes (correct)

When there is a sudden lack of nutrients

Which intracellular system is NOT vulnerable to injury?

Blood vessel elasticity Signup and view all the answers

What is the main role of the cytosolic free calcium level in cells?

To be maintained at extremely low levels Signup and view all the answers

Which type of injury results from the body's immune system's response?

Immunologic reactions Signup and view all the answers

What is one of the consequences of increasing levels of cytosolic calcium?

Induction of apoptosis Signup and view all the answers

Which condition is closely linked to atherosclerosis due to dietary factors?

Diets high in animal fats Signup and view all the answers

What is the primary cause of cytoplasmic eosinophilia?

Cytoplasmic acidosis Signup and view all the answers

Which type of necrosis is characterized by preservation of cell structural outlines?

Coagulative necrosis Signup and view all the answers

What kind of injury leads to fatty change in liver and myocardial cells?

Chemical injury Signup and view all the answers

What describes Karyorrhexis in nuclear changes?

Fragmentation of a pyknotic nucleus Signup and view all the answers

What is the primary process involved in necrosis?

Enzymatic digestion and protein denaturation Signup and view all the answers

Which statement about gangrenous necrosis is true?

It describes ischaemic coagulative necrosis with superimposed infection. Signup and view all the answers

Which structure undergoes dilatation and detachment of ribosomes during necrosis?

Endoplasmic reticulum Signup and view all the answers

What type of necrosis is primarily associated with tuberculous infection?

Caseous necrosis Signup and view all the answers

What role do free radicals play in cellular injury?

They mediate chemical and radiation injuries. Signup and view all the answers

Which chemical species is a product of the reduction of molecular oxygen during redox reactions?

Superoxide radicals Signup and view all the answers

Which of the following is NOT a consequence of oxygen free radical interactions with cellular components?

Increased cellular ATP production Signup and view all the answers

What causes the rapid breakdown of the endoplasmic reticulum when carbon tetrachloride is metabolized in the liver?

Membrane phospholipid peroxidation Signup and view all the answers

What is the main feature of hydropic changes seen in reversible cell injury?

Presence of clear vacuoles in the cytoplasm Signup and view all the answers

Which of the following best describes the process of chemical injury in cells?

Reactive metabolites must be generated from certain chemicals. Signup and view all the answers

What is a primary factor that leads to oxidative damage in cells?

Formation of unstable free radicals Signup and view all the answers

How do transition metals like Copper and Iron contribute to free radical formation?

They accept or donate electrons. Signup and view all the answers

What characterizes fat necrosis following acute pancreatitis?

Hydrolysis of triglyceride esters within fat cells Signup and view all the answers

What triggers the process of apoptosis?

Activation of certain receptors like FAS and TNF Signup and view all the answers

What is the result of apoptotic cell death?

Formation of apoptotic bodies for phagocytosis Signup and view all the answers

In which situation would apoptosis typically occur?

In the deletion of autoreactive T cells in the thymus Signup and view all the answers

What is a common feature of intracellular accumulations?

They can result from both normal and abnormal substances Signup and view all the answers

Which of the following statements about apoptosis is true?

The nuclear chromatin becomes condensed during the process Signup and view all the answers

What can lead to abnormal intracellular accumulation?

Normal substance produced at an inadequate metabolic rate Signup and view all the answers

Which condition indicates a storage disease?

Inadequate enzymatic function leading to accumulation Signup and view all the answers

What term refers to the deposition of calcium in dead or dying tissues despite normal serum calcium levels?

Dystrophic calcification Signup and view all the answers

Which process involves an increase in cell size due to increased synthesis of structural proteins?

Hypertrophy Signup and view all the answers

What causes metastatic calcification to occur?

Hypercalcæmia Signup and view all the answers

Which condition is NOT a cause of hypercalcemia?

Inadequate nutrition Signup and view all the answers

In which organs is metastatic calcification predominantly found?

Kidneys and lungs Signup and view all the answers

What is atrophy characterized by?

Shrinkage in the size of the cell Signup and view all the answers

Which cellular adaptation results from a normal physiological response to hormonal stimulation, such as in pregnancy?

Hypertrophy Signup and view all the answers

What is the consequence of extensive nephrocalcinosis?

Mild impairment of organ function Signup and view all the answers

Study Notes

Cell Injury

Cell injury occurs when cells are unable to adapt to stress or stimuli.
Two main types of cell death:
- Necrosis: Cell death due to injury, characterized by swelling, protein denaturation, and organelle breakdown.
- Apoptosis: Programmed cell death occurring normally or under specific conditions.
Causes of Cell Injury:
- Hypoxia: Inadequate oxygen supply affecting aerobic respiration.
- Physical agents: Trauma, temperature extremes, radiation, electric shock, pressure changes.
- Chemicals and drugs: Alter membrane permeability, osmotic balance, or enzyme function.
- Microbiologic agents: Viruses, bacteria, and parasites.
- Immunologic reactions: Immune system responses causing cell damage.
- Genetic defects: Inherited disorders like Down syndrome and sickle cell anemia.
- Nutritional imbalances: Protein-calorie deficiency, vitamin deficiencies, and high animal fat diets.
- Aging: Cellular processes decline with time.

Mechanisms of Cell Injury

Cell response to injury depends on type, duration, and severity.
Four main intracellular systems are vulnerable:
- Cell membrane integrity: Affects ionic and osmotic balance.
- Aerobic respiration: Energy production.
- Protein synthesis: Producing essential molecules.
- Genetic apparatus: DNA function and repair.

Free Radical Mediation of Cell Injury

Free radicals: Unstable molecules with unpaired electrons, highly reactive.
Implicated in chemical and radiation injury, oxygen toxicity, aging, microbial killing, inflammation, and tumor destruction.
Sources of free radicals within cells:
- Absorption of radiant energy (e.g., water hydrolysis to OH• and H•).
- Redox reactions (normal metabolism, generating superoxide radicals, hydrogen peroxide, and hydroxyl radicals).
- Enzymatic catabolism of oxygenous chemicals (e.g., CCl4 conversion to CCl3• in the liver).

Chemical Injury

Two main mechanisms:
- Direct combination with critical components: Mercury binding to sulfhydryl groups, inhibiting ATP transport.
- Conversion to reactive metabolites: P-450 oxidases in the SER convert chemicals to toxic forms (e.g., CCl4 to CCl3•).

Patterns of Acute Cell Injury

Reversible Cell Injury:
- Light microscopic changes:
  - Cell swelling (hydropic changes or vacuolar degeneration).
  - Cytoplasmic eosinophilia (acidic cytoplasm and loss of ribosomes).
  - Fatty change (seen in hypoxic and chemical injury in liver and heart).
- Ultrastructural changes:
  - Plasma membrane blebbing, microvilli distortion, loosened intercellular attachments.
  - Mitochondrial swelling and amorphous densities.
  - Endoplasmic reticulum dilatation, ribosome detachment, and polysome dissociation.
  - Nuclear alterations (disaggregation of granular elements).

Necrosis

Morphologic changes following cell death in living tissue.
Result of enzymatic digestion and protein denaturation.
Cytoplasmic changes: Eosinophilia, glassy appearance, vacuolation, and calcification.
Nuclear changes: Karyolysis (DNA digestion), pyknosis (nuclear shrinkage and increased basophilia), karyorrhexis (pyknotic nucleus fragmentation).

Types of Necrosis

Coagulative necrosis: Preservation of structural outlines due to protein denaturation (e.g., myocardial infarction).
Liquefactive necrosis: Caused by bacterial or fungal infections, leading to liquefaction (e.g., brain).
Gangrenous necrosis: Ischemic coagulative necrosis with superimposed infection (wet gangrene).
Caseous necrosis: Cheesy, white appearance seen in tuberculosis, with amorphous granular debris.
Fat necrosis: Focal fat destruction due to pancreatic enzymes (e.g., pancreatitis).

Apoptosis

Programmed cell death occurring in normal and pathological conditions.
Features: Single or clusters of cells with intense eosinophilic cytoplasm, condensed nuclear chromatin, karyorrhexis, cell shrinkage, and fragmentation into apoptotic bodies.
Does not elicit inflammation.
Initiation: Withdrawal of growth factors, receptor engagement, injury by radiation, toxins, and free radicals, intrinsic protease activation.

Intracellular Accumulations

Normal cells may accumulate abnormal substances.
Categories:
- Excess normal endogenous substance (e.g., fatty change in the liver).
- Accumulation due to metabolic defects (storage diseases).
- Deposition in dead or dying tissues (dystrophic calcification).

Metastatic Calcification

Occurs in normal tissues due to hypercalcemia.
Causes: Hyperparathyroidism, tumors, vitamin D intoxication, milk alkali syndrome, sarcoidosis, renal failure.
Location: Interstitial tissues, kidneys, lungs, gastric mucosa.

Cellular Adaptations of Growth and Differentiation

Atrophy: Shrinkage of cell size due to loss of cell substance.
Causes: Decreased workload, loss of innervation, decreased blood supply, inadequate nutrition, loss of endocrine stimulation, aging.
Biochemically: Decreased synthesis, increased catabolism, or both.

Hypertrophy

Increase in cell size due to increased protein synthesis and organelles.
Leads to an increase in organ size.

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Description

Explore the concepts of cell injury, focusing on necrosis and apoptosis. This quiz covers the causes of cell injury, including hypoxia, physical agents, chemicals, microbiologic agents, immunologic reactions, and nutritional imbalances. Test your knowledge on how these factors lead to cell damage and death.