Cell Injury

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Cell injury
In this topic we are going to cover
Cell injury
Causes of cell injury
Mechanism of cell injury
Morphologic alterations in cell injury
Morphologic types of necrosis
Objectives
Describe cell injury
List the causes of cell injury
Discuss how depletion of ATP causes cell injury
Describe how mitochondrial damage cause cell injury
Explain the mechanism of cell injury by free radicals
Discuss how calcium ion influx cause cell injury

Cell injury
cell injury results when cells are stressed so severely that they are no longer able to adapt or when cells are exposed to inherently damaging agents or suffer from intrinsic abnormalities. Injury may progress through a reversible stage and culminate in cell death   Reversible cell injury.

In early stages or mild forms of injury, the functional and morphologic changes are reversible if the damaging stimulus is removed.   

Cell injury
The hallmarks of reversible injury are reduced oxidative phosphorylation with resultant depletion of energy stores in the form of adenosine triphosphate (ATP), and cellular swelling caused by changes in ion concentrations and water influx. In addition, various intracellular organelles, such as mitochondria and the cytoskeleton, may also show alterations. Causes of Cell Injury

Oxygen Deprivation.
Hypoxia is a deficiency of oxygen, which causes cell injury by reducing aerobic oxidative respiration. Hypoxia is an extremely important and common cause of cell injury and cell death. Causes of hypoxia include ischemia, cardiorespiratory failure, and decreased oxygen-carrying capacity of the blood, after severe blood loss. Depending on the severity of the hypoxic state, cells may adapt, undergo injury, or die.

Causes of Cell Injury
Physical Agents.
Physical agents capable of causing cell injury include mechanical trauma, extremes of temperature (burns and deep cold), sudden changes in atmospheric pressure, radiation, and electric shock. Chemical Agents and Drugs.

From simple chemicals such as glucose and salt or oxygen to poisons and environmental chemicals can cause cell injury. Causes of Cell Injury
Infectious Agents.
Virus to large helminthes cause cell injury.
Immunologic Reactions.
Immune reaction and autoimmunity can cause cell injury
Genetic Derangements. chromosomal anomaly, enzyme defects in inborn errors of metabolism, accumulation of damaged DNA or misfolded proteins can cause cell injury. Nutritional Imbalances.
Nutritional imbalances continue to be major causes of cell injury. Malnutrition (under nutrition and over nutrition

Mechanisms of Cell Injury
The mechanisms responsible for cell injury are complex.
There are, however, several principles that are relevant to most forms of cell injury:  The cellular response to injurious stimuli depends on the nature of the injury, its duration, and its severity.  The consequences of cell injury depend on the type, state, and adaptability of the injured cell. The cell's nutritional and hormonal status and its metabolic needs are important in its response to injury.

Mechanisms of Cell Injury
When the striated muscle cell in the leg is deprived of its blood supply, it can be placed at rest and preserved; not so the striated muscle of the heart. Exposure of two individuals to identical concentrations of a toxin, such as carbon tetrachloride, may produce no effect in one and cell death in the other. This may be due to genetic variations affecting the amount and activity of hepatic enzymes that convert carbon tetrachloride (CCl4) to toxic by-products.

Mechanisms of Cell Injury
With the complete mapping of the human genome, there is great interest in identifying genetic polymorphisms that affect the responses of different individuals to injurious agents.    Cell injury results from different biochemical mechanisms acting on several essential cellular components.

Mechanisms of Cell Injury

The cellular components that are...
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