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Irreversible Cell injury(Cell Death)

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CELLS REACT TO INJURIOUS

STIMULI

ADAPTING SUSTAINING REVERSIBLE INJURY SUFFERING IRREVERSIBLE INJURY

AND DYING

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TYPES OF CELLDEATH APOPTOSIS(normal death

or physiologic death)

NECROSIS(premature or

untimely death due to

causes(Pathologic death)

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NECROSIS

It refers to a series of morphologic changes that

follow cell death in living tissues

OR is the gross and light-microscopic

appearances that indicate cell death.

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The surrounding living tissue almost

always show inflammatory reaction

The necrotic cell undergo lysis

Autolysis is the dead cell being self-

digested by its lysosomal enzymes, while

heterolysis is the cell being digested by

the body's living white cells.

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Morphology of Necrotic Cells

Increased Eosinophilia of cytoplasm

- loss of RNA (basophilia)

- denatured cytoplasmic protein bind tightly toeosin

Nuclear Changes

- Pyknosis ( shrinkage & basophilia)

- Karyorrhexis (Fragmentation of pyknotic nuclei)

- Karyolysis (fading of chromatine DNAase effect Myelin figure (EM)

large, whorled phospholipid mass (phospholipidprecipitate)

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HISTOLOGIC FEATURES OF COAGULATIVENECROSIS

Normalcell Reversible

cell injury

withcytoplasmic

& organelle

swelling,

blebbing &

ribosome

detachment

Irreversible

cell injury with

rupture of

membrane &

organelles, &

nuclear

pyknos is

Karyorrhexis

Karyolysis

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Myocardial infarction (coagulative necrosis)

Cytoplasmic eosinophilia & nuclear karyolysis

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Pathogenesis of necrosis1. Denaturation of intracellular proteins

( structural & enzymatic)

2. Enzymetic digestion of the cell

(Auto & Heterolysis)

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Morphologic Pattern of Necrotic

Cell mass

TYPES OF NECROSIS

COAGULATIVE NECROSIS

LIQUEFACTIVE NECROSIS

CASEOUS NECROSIS

FAT NECROSIS

FIBRINOID NECROSIS

GANGRENE

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COAGULATIVE NECROSIS

Death of groups of cells with preservation of

general tissue architecture-tombstone

appearance for at least a few days.

Affected tissue is firm due to denaturation of

structural & enzymatic proteins(intracellular

acidosis)

Example . Ischemic injury of heart, kidney,

,spleen.

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Coagulative necrosis

Preservation of

structure

Firm

Protein

denaturation

Hypoxic tissue

death (except

brain)

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Spleen; Coagulative necrosis

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The microscopy is distinctive. After loss of their

nuclei, the cytoplasm of the cells remains intact fordays. The "tombstones" reveal the structure of the

living tissue. If the patient lives, the edges of the

necrotic area become inflamed, and eventually the

dead cells will be removed by white blood cells

RULE: Unless otherwise specified in this section,

the death of a group of cells will result in

coagulation necrosis (Ischemic necrosis=Infarction)

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Kidney infarct exhibiting coagulative necrosis, with loss of nuclei

and clumping of cytoplasm but with preservation of basic outlines

of glomerular and tubular architecture

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DEATH:

LIGHT MICROSCOPY

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Liquefactive Necrosis

- focal bacterial (or fungal) infections

accumulation of inflammatorycells

- hypoxic death of cells within CNS

Morphologic pattern of Necrotic

Cell mass

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LIQUEFACTIVE NECROSIS

(* "colliquative necrosis" in Europe): Whenthe cells die, they are rapidly destroyed by

lysosomal enzymes, either their own or

those from neutrophilic leukocytes The tissue becomes liquid viscous mass

Material is creamy yellow in color

Seen in ischemia of brain, abscess

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Normal brain Liquefactive necrosis

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CASEOUS NECROSIS

*Type of coagulative necrosis*Tissue is cheesy white in appearance

*All the cells in the area die & surrounded by

inflammatory cells (granulomatousinflammation).

*The tissue architecture is completely

distructed & turn into friable tissue.*Seen in tuberculous infections &certain

fungal infections (as Histoplasmosis)

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A tuberculous lung with a large area ofcaseous

necrosis

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Caseous necrosis of lymph nodes

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Caseous necrosis with Giant cells

http://www.pathology.vcu.edu/education/pathogenesis/images/1b-d.jpg

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Fat necrosis

Not a specific pattern

Focal areas of fat digestion

Usually via release of lipases from pancreas

Lipase releases free fatty acid (saponification)

from the local lipids (membranes, depot

triglyceride).

FFA combine with Ca to produce salt soaps

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Foci of Fat necrosis with saponification in the mesentry . The

areas of white chalky deposits represent calcium soap

formation at sites of lipid breakdown.

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Microscopic appearance of fat necrosis

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FIBRINOID NECROSIS

is a term for damage to the walls ofarteries which allows plasma proteins to

leak out, and precipitate in, the media

FIBRINOID NECROSIS

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FIBRINOID NECROSIS

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GANGRENE

("gangrenous necrosis") is not a separate

kind of necrosis at all, but a term fornecrosis that is advanced and visiblegrossly. The word gangrene comes from

the Latin word gangraena, an eating sore.Gangrene is death and decay of a bodypart mostly ischemic necrosis of limbs

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Gangrene is defined as the gradual destruction

of living tissue, due to an obstruction in thesupply of blood and oxygen to an area of the

body (Ischemia)

Gangrene = ischemic necrosis

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TYPES OF GANGRENE

.DRY GANGRENE

.WET GANGRENE

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Dry gangrene

This is mostly coagulative necrosis

without infection (free of infection). It is

usually brought on by frostbite, or poorcirculation that cause the tissues to

become dry & black.

DRY GANGRENE

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DRY GANGRENE

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dry gangrene (coagulative necrosis)

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WET GANGRENE

there's mostly liquefactive necrosis (i.e.,the typical foul-smelling, oozing foot

infected with several different kinds of

bacteria).

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"wet gangrene in patient with Diabetes

millitus

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Ischemic necrosis of the bowel (bowel infarction)