outline causes and pathogenesis of cell injury/death
describe the morphological changes of cell injury/death
Describe the process of apoptosis
Adapt or die!
Reaction patterns in a given cell/tissue is often limited
Degree of injury is a function of type, duration and severity of insult
Types of insult - hypoxia
Local e.g. embolus
Systemic e.g. cardiac failure
Oxygen problems e.g. altitude
Haemoglobin problems e.g. anaemia
E.g. cyanide poisoning
Types of insult - chemical
Many of the common poisons (arsenic, cyanide, mercury) interfere with cellular metabolism. If ATP levels drop below critical levels, affected cells will die.
The list of pharmaceuticals that may have toxic effects on cells is enormous. Some act directly, but most have their effect through breakdown metabolites. Metabolism of alcohol (a type of drug) to acetaldehyde is one example.
E.g. viruses can take over protein translation machinery and subvert it entirely to the production of new virions.
Types of insult - Physical
Direct Physical Effects
Exposure of tissue to extreme heat or cold results in direct injury that is often irreversible, resulting in a pattern of coagulative necrosis (see later).
Sudden changes in pressure can cause cellular disruption (e.g. a hammer blow to the thumb).
Electrical currents can cause direct breakdown of cellular membranes that may be irreversible.
Types of insult –immune
Inflammatory mediators such as interferons and interleukins
can alter both gene expression and cellular metabolism. The effects are designed to help cells combat an infectious process, but the resulting stress to the cells can be highly injurious and sometimes deadly.
Activation of complement
can result in direct attack on a cell's surface membrane.
Cytotoxic T-cells and NK cells
can mediate a direct attack on a target cell's and initiate the self-destruct cascade within a target cell.
Types of insult - nutrition
of protein, vitamins and/or minerals can lead to injury at the cellular level due to interference in normal metabolic pathways.
can likewise lead to cellular and tissue alterations that are detrimental e.g. fat is the biggest offender, or excess ingestion of "health supplements"