Describe the biochemical mechanism leading to cell membrane damage.

Mechanisms of cell Membrane Damage:

• Reactive oxygen species. Oxygen free radicals cause injury to cell membranes by lipid peroxidation.
• Decreased phospholipid synthesis. The production of phospholipids in cells may be reduced as a consequence of defective mitochondrial function or hypoxia, both of which decrease the production of ATP and thus affect energy-dependent biosynthetic pathways. The decreased phospholipid synthesis may affect all cellular membranes, including the mitochondria themselves.
• Increased phospholipid breakdown. Severe cell injury is associated with increased degradation of membrane phospholipids, probably due to activation of calciumdependent phospholipases by increased levels of cytosolic and mitochondrial Ca2+.
• Cytoskeletal abnormalities. Cytoskeletal filaments serve as anchors connecting the plasma membrane to the cell interior. Activation of proteases by increased cytosolic calcium may cause damage to elements of the cytoskeleton.

What are the morhological types of irreversible cell injury?

Morphological pattern of irreversible cell injury are as follows: 

A. Necrosis

• Coagulative necrosis
• Liquefactive necrosis
• Gangrenous necrosis
• Caseous necrosis
• Fat necrosis
• Fibrinoid necrosis

B. Apoptosis.

What are the causes of cell injury?

Causes of Cell Injury: 

The causes of cell injury range from the external gross physical violence of an automobile accident to subtle internal abnormalities, such as a genetic mutation causing lack of a vital enzyme that impairs normal metabolic function. Most injurious stimuli can be grouped into the following broad categories.

1. Oxygen Deprivation. Causes of hypoxia include reduced blood flow (celled ischemia), inadequate oxygenation of the blood due to cardiorespiratory failure, and decreased oxygen-carrying capacity of the blood, as in anemia or carbon monoxide poisoning (producing a stable carbon monoxyhemoglobin that blocks oxygen carriage) or after severe blood loss.

2. 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.

3. Chemical Agents and Drugs. Oxygen at high concentrations is toxic, Arsenic, Cyanide, Mercuric salts.

4. Infectious Agents. Rickettsiae, Bacteria, Fungi, and higher forms of parasites.

5. Immunologic Reactions. Injurious reactions to endogenous self-antigens are responsible for several autoimmune diseases.

6. Genetic Derangements.

7. Nutritional imbalance. Protein-calorie deficienciency, Deficiencies of specific vitamins, Atherosclerosis, Obesity.

What is cell injury? What are the types of cell injury?

Cell injury:

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.

Types of cell injury:

1. Reversible cell injury.

2. Irreversible cell injury or cell death.