Degeneration and Necrosis Flashcards
Cell Injury
Any biochemical or structural alteration that impairs the ability of the cell to function normally.
Four common causes of cell injury
- Hypoxia
- Free radicals and activated O2 species
- Some chemicals
- Viruses
Total loss of oxygen
anoxia
Deficiency of oxygen in the tissue
hypoxia
Inadequate oxygen in the presence of adequate blood supply
Anoxic anoxia
Decrease arterial blood flow and pressure with stagnation and decrease oxygen delivery
Ischemic anoxia
Failure of the cell to use available oxygen
Cytotoxic anoxia
Why are consequences of hypoxic anoxia greater in brain, heart, liver, and kidney?
-High metabolic rate
-With elaborated vascular system which shunts, anastomoses and double supply that protects them from hypoxia
-Duration and form of oxygen deficit are important determinants of cell injury
-Heart muscle extract 100% of the O2 from the whole volume of blood circulating in the myocardial capillaries.
Cellular changes in anoxia
- Mitochindrial shutdown
- Ion shifts in the cytoplasm
- Metabolic shift
- Membrane lyse
Define degeneration
means deterioration, Abnormal morphological changes or “sicked cells” . In general, considered as reversible if the function returns to normal
Patterns of cell degeneration
- Water loading
- Metabolite loading
- Storage loading
What pattern of cell degeneration is described as acute cell swelling and hydropic degeneration?
Water loading
Glycogen degeneration, fatty degeneration, and hyaline degeneration are what pattern of cell degeneration?
Metabolite loading
Lipidosis, mucopolysaccharidosis, mineralization and pigment loading are seen in what pattern of cell degeneration?
Storage loading
Describe the degenerative changes in the cell membrane
Forms variety of configuration due to peroxidation of unsaturated lipids in the CM by free radicals that leads to degeneration of the phospholipids layer and protein components of the cell
Separation of intracellular junction
Formation of holes which is fatal to the cell
Injury that leads to the Na and CL into the cell together with water
Describe the degenerative changes in the mitochondria
Loss of mitochondrial junction due to decrease ATP
Condensation with contraction of matrix
Swelling after ion and water movement inside with rupture of the outer membrane
Tubular formation from inner membrane
Calcium and phosphate deposition
Sometimes formation of the megamitochondrion
Degenerative changes seen in the endoplasmic reticulum
May lose ribosomes, break up or become greatly dilated into vesicular structures or may form a dense whorls when injured
Degenerative changes seen in the lysosomes
Become quite prominent due to
Needs for digestion
Removal of particles brought into the cells by the process of heterophagy
Removal of degenerative components within the cell by the process of autophagy
One of the earliest recognizable microscopic changes following injury, Universal manifestation of cell injury
Acute cellular swelling
Severe acute cell swelling in which free water dilutes the cytoplasm. Common in epithelium and is called “ballooning degeneration”
Associated with blisters as seen in burns, bacterial toxins and epitheliotrophic viral diseases (FMD, VE,SVD. SVS)
Hydropic degeneration
Membrane bound pumps rapidly moves ions and water out of the cytosol into the cisternae of the ER, which expands to create large filled cytoplasmic vacuoles. Very much like Hydropic degeneration except that water in large cytoplasmic vacuoles
Vacuolar degeneration
What happens during glycogen degeneration?
Major deposits of glycogen in the liver, muscle, and kidney and this condition is essentially limited to these organs
Abnormal accumulation of fat in the cytoplasm of the parenchymal cell. Liver is the best known location of this lesion lesser in the renal tubular epithelium and in the myocardium. Also known as lipidosis or fatty liver.
Fatty degeneration
Excess lipids in the cells suggest that
-Long standing elevation of blood lipids
-Chronic hypoxia inhibiting lipid metabolizing enzymes
-Acute sub lethal injury that suppresses lipid pathways or,
-Chronic progressive metabolic disease arising from defective cell enzymes.
-Liver and kidney are apt to be involved in acute injury or metabolic disease.
Fatty liver is well known in diabetes in?
dogs
Fatty liver is well known as ketosis in?
Bovine
Also known as fatty replacement. The presence of fat in adipose cell that accumulate in tissues in which they are not normally present usually replacing atrophied tissues.
Fatty infiltration
A form of fatty infiltration in large areas of muscle having a pale or mottled color due to fatty infiltration
Steatosis
Cell death can occur in two ways, these are?
Accidental cell (necrosis), Programmed cell death
When the cell injury progressed to the point where irreversible cell injury occurs or passed the point of “no return”. Death of cells and tissues in the living animal
Necrosis
Involves the shrinkage or condensation of a cell with increased nuclear compactness or density. Nucleolus is no longer visible,
Loss of internal structure
Pyknosis
Fragmentation of chromatin into tiny basophilic granules due to rupture of the nuclear membrane
Fragmented bits may remain in the original place of the nucleus or scattered throughout the cytoplasm
Karyorrhexis
Refers to the earlier stage of cell death
Karyolysis
Karyolysis
-Nucleus appear as hollow sphere surrounded by a faint outline, or ghost of nuclear membrane
-Dissolution or lysis of the nuclear chromatin by nucleases from leaking lysosomes of dead cells
-Solubilized chromatin diffuses out of the leaky nuclear membrane into the cytosol and interstitial fluid
-When complete, nuclear membrane disappears
Nuclear changes during necrosis
loss of nucleus
Changes in the cytoplasm during nercosis
Depletion of the cytoplasmic glycogen
Increased eosinophilia of the cytoplasm
The cytoplasm tends to become less dense and ultimately disappears completely
Cyoplasmolysis
Changes in the whole cell during necrosis
-Loss of cell outline
-Loss of differential staining
-Loss of cell
Gross characteristic of a necrotic tissue
Dead tissue is paler than healthy one
Black if filled with blood
Dead tissue has less tensile strenght because of the enzymatic digestion of the cytoskeleton
Odors of putrefaction may emanate from or caused by saprophytic bacteria after gangrene or postmortem autolysis
Forms of necrosis
- Coagulative necrosis
- Liquefactive necrosis
- Caseous necrosis
Sequence of events during necrosis
Necrosis begins with cell swelling, the chromatin gets digested, the plasma and organelle membranes are disrupted, the ER vacuolizes, the organelles break down completely and finally the cell lyses, spewing its intracellular content and eliciting an immune response (inflammation).
Occurs when cells die due to a lack of blood supply
Coagulative necrosis
How can you identify coagulative necrosis grossly?
Tissue is gray to white unless filled with blood, it is firm, dense and often depressed compared to the normal tissue
Focal necrotic areas are ussually surrounded by zones of inflammation.
How can you identify coagulative necrosis microscopically?
The normal architecture of the tissue with its cellular components is recognizable, but the nuclie appear karyolitic, pyknotic, karyorrhectic or absent
The cytoplasm is strongly acidophilic
Rapid enzymatic dissolution of the cells that result in complete destruction. It occurs in bacterial infection that lead to suppuration or pus formation when proteolytic enzymes released from WBC converts dead WBC and cellular debris into liquid amorphous materials.
Liquefactive necrosis
How can you identify liquefactive necrosis grossly?
Lesion is a cavity with wall, small or large containing fluid that is usually yellow white and opaque
Wall cavity are frayed and irregular and more or less soft
Usually drained away by the lymphatic
Abscess is a localized collection of LN caused by suppuration deep in the tissue
How can you identify liquefactive necrosis microscopically?
Necrotic tissue appear as empty space without definitive lining with frayed and irregular edge that may show some feature of necrosis
Pink staining proteinaceous precipitate may or may not remain in the fluid
Abscess contain large number of neutrophils whose enzyme liquefied areas of dead tissues and themselves, leaving liquefied mass of cellular debris
It occurs when dead cells are converted into granular friable mass resembling cottage cheese. Occurs as part of typical lesions of tuberculosis, tularemia, syphilis, ovine caseous lymphadinitis, adenitis, and other granulomas.
Caseous necrosis
How can you identify a caseous necrosis microscopically?
There is loss of cell outline and differential staining
Cell wall and other histologic structures disappears, and the tissue disintegrates to form finely granular mass that has purplish color with H&E. resulting from the mixture of blue chromatin material with red material derived from the cytoplasm.
The normal architectural pattern is totally obliterated.
How can you identify caseous necrosis grossly?
White, grayish, or yellowish and is suggestive of milk curds or cottage cheese
Necrotic tissue is dry, slightly greasy and firm without any cohesive strength, rendering it easily separable into granular fragments with blunt instrument.
Fat is often decomposed into fatty acid and glycerin
Fat combine with metallic ions Na, K, and calcium to form soap-like compounds
Fat necrosis
a severe glassy or waxy hyaline degeneration or necrosis of striated muscle in acute infectious diseases.
Zenkers necrosis
serous atrophy of fat in the coronary groove of the heart. This lesion is commonly seen in cachexia.
Myxomatous Degeneration
Localized area of necrosis resulting from sudden obstruction of blood supply to the affected area.
Infarcts
Types of infarcts
Red/Hemorrhagic
Pale/Anemic
Infarcts in the kidney
Typically conical with the apex near the corticomedullary junction and the path of the arcuate arteries, anemic, multiple and often heal leaving only a narrow fibrous scar
Infacts in the spleen
almost always hemorrhagic, many shallow subcapsular infarcts – seen in hog cholera
Infacts of the myocardium
– rare in animals than in humans