Cell Injury Flashcards
Define cell injury
If the limits of adaptive responses to a stimulus are exceeded or if the cells are exposed to injurious agent or stress , deprived of essential nutrients or become compromised by mutations that effect the essential cellular constituents a sequence of reactions follows called as cell injury
Different tissue responses to cell injury
1.Altered physiological stimuli: cellular adaptation. Hyperplasia
Hypertrophy atrophy metaplasia
2.acute reversible injury : cellular swelling
Fatty change
Acute Irreversible injury: necrosis and apoptosis
3. Chronic injury: intracellular accumulations, calcification
4. Sublethal injury over a long span: cellular aging
Mechanism of cell injury
- Atp depletion
- Membrane damage/ defects in memb permeability
- Mitochondrial damage
- Accumulation of reactive o2 species……
- Influx of intracellular Ca++ causing damage to dna nd proteins
Role of ca++
Failure of ca++ pump leads to influx of ca++ causing activation of various enzymes that have damaging effects
Phospholipase
Protease
Endonuclease
Atpase….
Why does inflammation occur in necrosis
Necrotic cells lose their membrane integrity leading to the release of intracellular contents into the extracellular space
What are free radicals
Free radicals are chemical species that have a single unpaired electron in their outermost orbit
Generation of free radicals
1radiant energy absorption: uv rays and x rays
2. Reduction oxidation reactions
3. During inflammation
4. Transition metals like iron copper
5. Enzymatic metabolism
6. Nitric oxide
Pathological effects of free radicals
- Lipid peroxidation in membranes
- Oxidative modification of proteins
- Lesions in dna
Neutralization of free radicals
- Spontaneous deacy: these are inherently unstable.
O2^- decays into O2 in presence of water - Non enzymatic: antioxidants in the cytosol- lipid soluble vitamins like A and E
Ascorbic acid
Glutathione
Iron copper
Transferin lactoferin ferritin ceruloplasmin - Enzymatic:
.Catalase: h2o2 into o2 and h20
.Superoxide dismutase:
mn sod and cu zn sod
. Glutathione peroxidase
What are fatty changes
The term steatosis or fatty change refers to the abnormal accumulation of TG within parenchymal cells
Causes of fatty change
Alcohol abuse
Toxins
Protein malnutrition
DM
Obesity
Anoxia
Sites of fatty change
Liver
Heart
Muscle
Kidney
What causes fatty change in heart
Hypoxia eg. anaemia
Myocarditis eg. Diptheria
Pathological calcification
It is the abnormal tissue deposition of ca salts with smaller amts of other mineral salts
2 forms: dystrophic cal
Metastatic calc.
Dystrophic calcification causes
When deposition occurs locally in dying tissue despite normal serum levela of ca and in absence of derrangement in ca metabolism
1. In areas of necrosis
2. Atheromas of advanced atherosclerosis
3. Aging or damaged heart valves
4. Tuberculous lymphnode
Metastatic calc causes
The deposition of ca salts in otherwise normal tissues.
1. Inc secretion of pth
2. Resorption of bone tissue
3. Vit D related disorders
4. Renal failure
5. Milk alkali syndrome
6. Al intoxication
Sites of metastatic calc
Intestinal tissues if gastric mucosa
Kidneys
Lungs
Systemic arteries
Pulmonary veins
Chemical agents causing cell injury
Glucose or salt in hypertonic solution
O2 in high concentration
Env and air pollutants
Insecticides
Herbicides
Industrial or occupational hazard
Recreational drugs
Imp free radicals
Reactive o2 species
Superoxides
Hydrogen peroxide
Hydrxyl ion
Reactive nitrogen species
No
Onoo-
No2-
Ccl3 derived from ccl4
Define necrosis
Spectrum of morphological changes that follows cell death in living tissue largely resulting from progressive degradative action of enzymes on lethally injured cell
Apoptosis define
It is a pathway of cell death that is induced by a tightly regulated intracellular program in which cells that are destined to die activate enzymes that degrade the cells own nuclear dna and cytoplasmic proteins
Nuclear changes in necrosed cell
1.Karyolysis: basophilia of chromatin may fade reflecting dnase activity
2. Pyknosis: nuclear shrinkage and increased basophilia
3. Karyorrhexis: pyknotic or partially pyknotic nucleus undergoes fragmentation and disappears totally
Define gangrene
It is necrosis of tissue with superimposed putrefaction
Types of gangrene
Dry gangrene : because of lack of arterial blood supply.
Moist gangrene: due to obstruction of both arterial and venous drainage. Particularly in moist areas
Gas gangrene: caused mainly by clostridium perfringes
Rarely by c. Histolyticum
C. Novyi and c. Septicum
