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Overview. + Stress. Normal cell. Adapted Cell. - Stress. +Stress. Injury. - Stress. Reversibly injured cell. Apoptosis. Irreversibly Injured cell. Dead cell. Necrosis. LO. Define necrosis Enlist types of necrosis

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Adapted Cell

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Overview

+ Stress

Normal

cell

Adapted

Cell

- Stress

+Stress

Injury

- Stress

Reversibly

injured cell

Apoptosis

Irreversibly

Injured cell

Dead cell

Necrosis


LO

  • Define necrosis

  • Enlist types of necrosis

  • Identify morphological (gross and microscopic) features of different types of necrosis on image.

  • Enlist three stages in loss of nucleus resulting in cell death

  • Define apoptosis


(1) Definition: Localized death of cell or tissue occurring in the living body.


(2) Cell death is recognized by:

①Ultrastructural changes

  • Margination or progressive loss of nuclear chromatin

  • Focal rupture of the nuclear membrane

  • Breakdown of the plasmalemma.

  • Development of flocculent densities in mitochondria.


②Changes in the nucleus.

  • Pyknosis: condensation of chromatin of chromatin and shrinkage of the nucleus.

  • Karyorrhexis: fragmentation of the nucleus.

  • Karyolysis: dissolution of the nucleus.


Normal Pyknosis Karyorrhexis Karyolysis

(参照武忠弼 病理学规划教材第一版 人民卫生出版社1979,修改)


③Changes in cytoplasm staining

  • Opacification: denaturation of proteins lead to aggregation with resultant opacification of the cytoplasm.

  • Eosino0.philia: exposure of basic amino groups results in increased affinity for acidic dyes such as eosin.


④Biochemical changes

  • Release of K+ by dead cells.

  • Release of enzymes into the blood. e. g. increased plasma levels of creatine kinases, lactic dehydrogenase and aspartate aminotransferase.

  • Release of protein or protein breakdown products into the blood.


Morphology of Necrotic Cells

  • Increased Eosinophilia

    - loss of RNA (basophilia)

    - denatured cytoplasmic protein

  • Nuclear Changes

    - Pyknosis

    - Karyorrhexis

    - Karyolysis

  • Myelin figure

    – large, whorled phospholipid mass (phospholipid precipitate)


HISTOLOGIC FEATURES OF COAGULATIVE NECROSIS

Karyorrhexis

Normal cell

Reversible cell injury with cytoplasmic & organelle swelling, blebbing & ribosome detachment

Irreversible cell injury with rupture of membrane & organelles, & nuclear pyknosis

Karyolysis


Morphologic pattern of Necrotic Cell mass

  • Coagulative necrosis special types of coagulative necrosis

  • Liquefactive necrosis

  • Caseous necrosis

  • Fat necrosis

  • Fibrinoid necrosis


Types:

① Coagulative necrosis:

Gross features: The necrosis area is swollen, firm and pale.

LM: cell detail is lost, but architecture preserved. The dead cells retain their outline but only indistinctly.

This type of necrosis is frequently caused by lack of blood supply and is exemplified well in infarcts of solid organs, e. g. heart, spleen, kidney.


This is an example of coagulative necrosis. This is the typical pattern

with ischemia and infarction (loss of blood supply and resultant tissue

anoxia). Here, there is a wedge-shaped pale area of coagulative necrosis

(infarction) in the renal cortex of the kidney.


Coagulative necrosis of the left ventricular wall

(From ROBBINS BASIC PATHOLOGY,2003)


Ischemic necrosis of the myocardium

A, Normal myocardium.

B, Myocardium with coagulation necrosis


Special types of coagulative necrosis

B. Gangrene

Definition: necrosis of big tissue with superadded putrefaction, black, fou-smelling appearance.

Necrosis of big tissue putrefactive black, green

Or organ or limb organisms infection appearance

(black or green due to breakdown of haemoglobin)


Types of gangrene:

a. Dry gangrene:

Conditions: only occurs on the skin surface following arterial obstruction. It is particularly liable to affect the limbs, especially the toes.

Character: mummification


Dry gangrene


Types of gangrene:

b. Wet gangrene:

Conditions: Both arterial and venous obstruction; wet in environment;

Character: wet swollen, foul-smelling, black or green.

Commonly in small intestine, appendix, lung, and uterus, also in limbs.


Moist gangrene


Types of gangrene:

c. Gas gangrene:

Conditions: deep contaminated wounds in which there is considerable muscle damaged by gas formation bacteria.

Character: swollen obviously, gas bubbles formation. The infection rapidly spreads and there is associated severe toxaemia.

Only occasionally in civilian practice but is a serious complication of war wounds.


②Liquefactive necrosis:

Soft and liquid grossly. Enzymes digest the cell and convert it to a formless proteinaceous mass. Ultimately, discharge of the contents forms a cystic space. i. e. central nervous system after ischemic injury; abscesses.


Morphologic Pattern of Necrosis

  • Caseous necrosis

    :gross appearance

    :microscopic – granulomatous inflammation


A tuberculous lung with a large area of caseous necrosis


Tuberculous granuloma showing an area of central necrosis, epithelioid cells, multiple Langhans-type giant cells, and lymphocytes.


Special type:

Fat necrosis:

Grossly: Opaque and chalky

LM: outline of necrotic fat cells filled with amorphous basophilic material (calcium soaps).

i. e. Digestion of peritoneal fat by pancreatic enzymes in pancreatic inflammation.


Foci of fat necrosis with saponification in the mesentery


Fibrinoid necrosis:

  • Definition: This is not a true degeneration but a strongly eosinophilic stain like fibrin.

  • Location: interstitial collagen and blood vessels (small artery and arteriole)

  • Nature: one kind of necrosis.

  • e. g. in allergic reactive diseases: active rheumatism, polyarteritis nodose.

  • in non-allergic reactive diseases: malignant hypertension.


Fibrinoid change in blood vessel


(4) Consequences of necrosis

① Acute or chronic inflammation

② Immunological reactions to sub cellular components released by dead tissue or self-antigens altered by denaturation.


③ lysis and absorption

④ Isolation and discharge: ulceration and cavity formation

⑤ organization

⑥encapsulation, calcification.


Apoptosis

  • Programmed cell death

  • Physiologic

  • pathologic


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