its for pathology

1. Causes and Types of cell
injury

2. Causes
• Physical agents such as heat or radiation can damage a cell by literally
cooking or coagulating their contents.
• Impaired nutrient supply, such as lack of oxygen or glucose, or impaired
production of adenosine triphosphate (ATP) may deprive the cell of
essential materials needed to survive.
• Metabolic: Hypoxia and Ischemia
• Chemical Agents
• Microbial Agents:-Virus & Bacteria
• Immunologic Agents: Allergy and autoimmune diseases such
as Parkinson's and Alzheimer's disease.
• Genetic factors: Such as Down's syndrome and sickle cell anemia

3. Types of damage
• Some cell damage can be reversed once the stress is removed or if compensatory
cellular changes occur. Full function may return to cells but in some cases, a
degree of injury will remain.
• Reversible
• Cellular swelling: Cellular swelling (or cloudy swelling) may occur due
to cellular hypoxia, which damages the sodium-potassium membrane pump; it is
reversible when the cause is eliminated
• Fatty change: The cell has been damaged and is unable to adequately metabolize
fat.

4. Irreversible
• Necrosis:
• Necrosis is characterised by cytoplasmic swelling, irreversible damage to the
plasma membrane, and organelle breakdown leading to cell death.
• Apoptosis:
• Apoptosis is the programmed cell death of superfluous or potentially
harmful cells in the body.

5. Repair
• When a cell is damaged the body will try to repair or replace the cell to continue
normal functions.
• If a cell dies the body will remove it and replace it with another functioning cell,
or fill the gap with connective tissue to provide structural support for the
remaining cells.
• The motto of the repair process is to fill a gap caused by the damaged cells to
regain structural continuity.
• Normal cells try to regenerate the damaged cells but this cannot always happen.
• Asexual reproduction is what repairs cells

6. Regeneration
• Regeneration of parenchyma cells, or the functional cells, of an organism. The
body can make more cells to replace the damaged cells keeping the organ or tissue
intact and fully functional.
• Replacement
• When a cell cannot be regenerated the body will replace it with stromal connective
tissue to maintain tissue/organ function. Stromal cells are the cells that support the
parenchymal cells in any organ. Fibroblasts, immune cells, pericytes, and
inflammatory cells are the most common types of stromal cells.

7. Biochemical changes in cellular injury
• ATP (adenosine triphosphate) depletion is a common biological alteration that
occurs with cellular injury.
• This change can happen despite the inciting agent of the cell damage. A reduction
in intracellular ATP can have a number of functional and morphologic
consequences during cell injury. These effects include:
• Failure of the ATP dependent pumps (Na+/K+ pump and Ca2+ pump), resulting in a
net influx of Na+ and Ca2+ ions and osmotic swelling.
• ATP-depleted cells begin to undertake anaerobic metabolism to derive energy
from glycogen which is known as 'glycogenolysis'.
• A consequent decrease in the intracellular pH of the cell arises, which mediates
harmful enzymatic processes.
• Early clumping of nuclear chromatin then occurs, known as 'pyknosis', and leads
to eventual cell death.