Cellular Injury

Cellular Injury

• Cells are complex units and can be injured in many ways. 
•  A person’s state of wellness and disease is reflected in cells. Injury to any of the cells’ components can lead to illness. 
•  The mechanisms responsible for cell injury leading to necrotic cell death are numerous and interrelated.  They are dependent on a delicate balance between intracellular and extracellular events.  Whether the cell is reversible or irreversible is dependent on intensity and duration of the injury and the type of cell involved.

Stresses damage cells by DNA damage, damage to vital cell proteins including enzyme

Lipid peroxidation and injury to cell membranes

Remember TIPD

Toxic injury – endogenous exogenous

Infectious injury – viral bacterial

Physical – thermal - mechanical

Deficit injury –  water oxigen nutrients

Causes: 

Hypoxia:	oxygen deprivation resulting in interruption of oxidative metabolism and generation of ATP.
Physical Agents:	responsible for cell and tissue injury from mechanical forces, extremes of temperature and electrical injuries. cellular membrance are injured by direct contact with cellular and chemical components of immune and inflammatory responces, temp extreme, electrical ionizing rad, illumination of florescent lighting, mechanical injury and noise, AC more dangerous violent muscle contrations
Chemical Agents and Drugs:	Multiple chemical agents are found in the environment. Drugs such as ethylene alcohol (ETOH), prescription or “over the counter” drugs and street drugs can be injurious cells and tissues. – deficit alcohol
Biologic Agents:	Virus’, bacteria and parasites can replicate and continue tissue disruption. – infection,  produce injury by invading and destroying cells producing toxins inducing hypersensitivity
Ionizing Radiation:	Can cause ionization of atoms or molecules in the cell, directly hit target molecules in the cell or aid in the production of free radicals that interact with critical cell function
Nutritional Imbalances:	Excess and deficiencies predispose the cells to injury

Mechanisms: Complex and varied. Most injuries fall under one of three major categories.

Depletion of ATP:	Usually associated with hypoxia and chemical cellular injury.
Free Radical Injury:	Formation: Unstable chemical species with a unpaired electron in the outer orbit. Effects: Wide ranging effects including lipid perioxidation, oxidative modification of proteins, and DNA effects. Defenses against Free Radicals: Under normal circumstances cells have chemical mechanisms that protect against the effects of free radicals. Free radical scavengers include Vitamins E, A and C.
Impaired calcium homeostasis:	ischemia and certain toxins disrupt the normally low intracellular calcium levels predisposing damaging effects on the cell.