irreversible cell injury

Reversible If stressor removed, and

If cell damage mild: cells survive

Irreversible --> cell death. Types:Apoptosis: normal (leaves falling) as in

menses, aging PROGRAMMED

Necrosis: patho-logical...

Autolysis: after death of entire organism (dissolution of dead

cells by its own digestive enzymes)

The first is the inability to

reverse mitochondrial dysfunction (lack

of oxidative phosphorylation and ATP

generation) even after resolution of the original

injury.

The second is the development of profound

disturbances in membrane function.

DEFINITION:

Death of a group of contiguous

cells within a living tissue or organ

Affect both nucleus and cytoplasm

Unregulated cell death with

inflammation

Cytoplasmic

Nuclear

Cytoplasmic changes :

Cytoplasmic eosinophilia due to loss of normal basophilia& increased binding of eosin to denaturatedproteins

(Granular or homogenous glassy)

Nuclear changes:

Pyknosis: shrinkage-increased staining with haematoxylin

Karyorrhexis: fragmentation

Karyolysis: total disappearance

Coagulative

Liquefactive

Caseation

Fat

In: infarcts of kidney, heart, spleen

Gross: pale , yellow, opaque, firm

Mic.: All cellular details are lost but general

architecture of the tissue is preserved

Surrounding tissue----acute inflammation

Ex: Infarction - heart

Infarction - kidney

In: centers of pyogenic abscess

amoebiasis

infarcts of C.N.S.

Necrotic tissue---completely liquified---turbid

fluid----absorbed----space

Ex: Brain - infarction

Amoebiasis ---liver

In: Tuberculosis

Necrotic tissue is partially liquefied---cheesy

material (caseation)

Mic: Both cellular details & general architecture of

dead tissue are lost---structureless eosinophilic

material

Traumatic: in female breast

Enzymatic: in acute hemorrhagic

pancreatitis

Gross: opaque & white

fat cells appear cloudy, surrounded by

chronic inflammatory

cells, histiocytes, foreign body giant cells

(programmed cell death)

Definition: death of individual cells

surrounded by viable cells

when a cell dies through activation of an

internally suicide program

It is an active process—energy dependent

Does not elicit inflammatory response

May be physiologic or pathologic

PHYSIOLOGIC

During embryogenesis e.g. removal of

interdigital webs during embryonic development

of toes and fingers

Hormone-dependent e.g. endometrial cellloss in

menstruation

PATHOLOGIC

Irradiated tissues

Cell death induced by cytotoxic T-lymphocytes

Viral infections e.g. viral hepatitis

Cell death in tumours

Necrosis

Death of groups of cells

A passive process—not energy-dependent

Elicits inflammatory response

Always pathologic

Apoptosis

Death of individual cells

Active process—energy-dependent

Does not elicit inflammatory response

May be pathologic or physiologic

Definition:

-abnormal accumulation of triglycerides within parenchymal cells

Sites:

Liver (the most common)

Others, heart, kidney,--

Pathogenesis:

Excessive accumulation of triglycerides within the liver may result from defects in any one of the events in the sequence from fatty acid entry to lipoprotein exit

Congestive heart failure

Diabetes mellitus

Severe anaemia

Ischaemia

Septicaemia

Poisons

malnutrition

In all organs, fatty change appears as clear

vacuoles within parenchymal cells

Due to fat solvents used in paraffin

embedding

To identify fat, frozen tissue sections are

stained with Sudan IV or Oil Red-O---orange-

red colour

When mild - - - no effects on cell function

Severe - - - - - -impair cell function