Cell Injury
CELL INJURY: CAUSES OF CELL INJURY, MECHANISMS OF REVERSIBLE AND IRREVERSIBLE CELL INJURY.
CELL INJURY.
Causes of cell injury range from gross mechanical external causes to mild endogenous causes as genetic lack of enzymes etc.
Virtually all forms of tissue injuries start with molecular or structural alterations in cells.
Under normal conditions, the cells are in:
❖ homeostastatic „steady“ state
Normal cell is confined to relatively narrow range of functions and structure by its genetic programme to handle normal physiologic demands.
Cells react to adverse influence by
1- adapting
2- sustaining reversible injury
3- suffering irreversible cellular injury- cell death
More excessive stimuli (either physiologic or pathologic) may cause cellular adaptation -in order to reach
❖ altered steady state
- for example, excessive work stress causes an increase in muscle mass that reflects the increase in size of the individual muscle fiber, results in higher level of metabolic activity –and new equilibrium is reached- hypertrophy
- on the other hand- atrophy- is adaptative response in which there is a decrease in the size and function of the cells- and results from a slow long-lasting decrease of blood supply
❖ if the limits of adaptative mechanisms are exceeded or when no adaptative response is possible- cell injury
• Reversible cell injury denotes pathologic changes that can be reversed when the stimulus is removed and the cellular injury has been mild. Cell injury is reversible only up to certain point.
• Irreversible cell injury denotes pathologic changes that are permanent and cause cell death, they cannot be reversed to normal state
for example: if the blood suply to heart muscles is cut off for 10-15 minutes- the myocardial cell experiences injury but it can recover to normal function, if the blood flow is cut off for longer period- the myocardial fiber dies-necrosis
CAUSES OF CELL INJURY
•
CELL INJURY.
Causes of cell injury range from gross mechanical external causes to mild endogenous causes as genetic lack of enzymes etc.
Virtually all forms of tissue injuries start with molecular or structural alterations in cells.
Under normal conditions, the cells are in:
❖ homeostastatic „steady“ state
Normal cell is confined to relatively narrow range of functions and structure by its genetic programme to handle normal physiologic demands.
Cells react to adverse influence by
1- adapting
2- sustaining reversible injury
3- suffering irreversible cellular injury- cell death
More excessive stimuli (either physiologic or pathologic) may cause cellular adaptation -in order to reach
❖ altered steady state
- for example, excessive work stress causes an increase in muscle mass that reflects the increase in size of the individual muscle fiber, results in higher level of metabolic activity –and new equilibrium is reached- hypertrophy
- on the other hand- atrophy- is adaptative response in which there is a decrease in the size and function of the cells- and results from a slow long-lasting decrease of blood supply
❖ if the limits of adaptative mechanisms are exceeded or when no adaptative response is possible- cell injury
• Reversible cell injury denotes pathologic changes that can be reversed when the stimulus is removed and the cellular injury has been mild. Cell injury is reversible only up to certain point.
• Irreversible cell injury denotes pathologic changes that are permanent and cause cell death, they cannot be reversed to normal state
for example: if the blood suply to heart muscles is cut off for 10-15 minutes- the myocardial cell experiences injury but it can recover to normal function, if the blood flow is cut off for longer period- the myocardial fiber dies-necrosis
CAUSES OF CELL INJURY
•