1. Cell injury-3

2. Morphology of irreversible cell injury
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Morphology of irreversible cell injury

3. * Light microscopy of irreversible cell injury
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* Light microscopy of irreversible cell injury
Pyknosis = Shrinkage and darkening of the nucleus.
Karyorrhexis = fragmentation and breakdown of the nucleus, (into "nuclear dust").
Karyolysis = dissolution of the nucleus.

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5. Nuclear pyknosis
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Karyorrhexis
Karyolysis

6. * Types of cell death:
Necrosis: local death of a group of cells within the living body.
Apoptosis: genetically controlled programmed single cell death.

7. * Types of necrosis: Coagulation necrosis. Liquefactive necrosis.
Caseation necrosis.
Fat necrosis.
Fibrinoid necrosis.

8. Coagulative necrosis * Mechanism:
Denaturation and coagulation of structural and enzymatic proteins due to intracellular acidosis.
Denaturation of lysosomal enzymes by intracellular acidosis prevents autolysis.
Preserving cell outlines and tissue architecture.
Acute ischemia is the most common cause.

9. Liquefactive necrosis
* Definition: necrosis with complete loss of cell and tissue structure due to liquefaction by hydrolytic enzymes.
* Mechanism:
Enzymes derived from either cell’s own lysosomes (autolysis) or from Neutrophils and macrophages (heterolysis).

10. Coagulative vs. Liquefactive necrosis
Coagulative necrosis
Focus of liquefactive necrosis

11. Necrotic material
with loss of cellular
architecture
Lung Abscesses

12. Neutrophils
Necrotic tissue

13. Caseation necrosis
It is a combination of coagulative and liquefaction necrosis. The tissue is firm (grossly) and without cellular details or tissue outline (microscopically).
Most commonly associated with tuberculosis

14. Caseous necrosis Lung: tuberculosis
B: Lymph node, mediastinal, histoplasmosis - Gross, cut surface.  The caseous necrosis in this case of fungal infection has a white, cheese-like appearance. Caseous necrosis has a similar appearance, irrespective of the tissue involved.
This patient has miliary tuberculosis. The lesions look like millet seeds.
Lung: tuberculosis

15. Caseous necrosis Lung, pulmonary tuberculosis - Low power:
The area of caseous necrosis appears as amorphous, granular debris without preservation of the tissue architecture. At its edge, granulomatous inflammation with multinucleated giant cells is apparent.
Lung, pulmonary tuberculosis - High power (Glass slide 51)  Caseous nodules are pink and structureless, and unlike coagulation necrosis, architecture and cell outlines have been largely destroyed. Once again, Langhan’s giant cells are prominent. Notice that they have multiple nuclei.
As soon as you see a pinkish material, it is either liquefactive or caseous necrosis.
If it is caseous necrosis, they will ALWAYS show you Langhan’s giant cells.

16. Fat necrosis

17. 1. Traumatic fat necrosis
Secondary to trauma to fatty tissue.
Trauma to fatty tissue  acute inflammatory reaction (neutrophils)  healing by fibrous tissue and dystrophic calcification.
Commonly seen in women with pendulous breasts.
Clinical significance:
Scar tissue feels firm, retracts the overlying skin and shows calcifications on mammography.
“These findings also seen in breast cancer”.

18. 2. Enzymatic fat necrosis
Focal areas of fat destruction due to the action of pancreatic enzyme on fatty tissue located around pancreas.
Occurs as a complication of Acute pancreatitis.

19. Apoptosis

20. Genetically, programmed single cell death.
* Morphologically:
The cell membrane does not rupture.
The cell contents are not released into the extracellular space, and inflammation does not occur.
May be physiological or pathological.

21. * Morphologic appearance of apoptotic cells:
Cell shrinkage.
The cytoplasm becomes deeply esinophilic.
The nucleus becomes pyknotic then fragments.
Formation of cytoplasmic buds.
Each nuclear fragment of go with a cytoplasmic bud and breaking off to form apoptotic bodies.
Phagocytosis of apoptotic bodies by adjacent cells or macrophages.
A lack of inflammatory response.

22. * Physiologic examples of apoptosis:
Embryogenesis.
Development of lumen within hollow organs (e.g bowel and heart).
Hormone-dependent involution in adults.
Post-lactational atrophy of breast.
Prostate atrophy following castration.
Involution of Thymus in the adult.

23. * Pathologic examples of apoptosis:
Councilman bodies = dead hepatocytes in viral hepatitis.
Psammoma bodies: apoptosis of neoplastic cell with subsequent calcification.
Tumor cell death by cytotoxic T cells.
Neurons that are lost in Alzheimer's disease.
HIV-positive T-lymphocytes die by apoptosis.

24. Apoptosis of epidermal Apoptotic cell in liver
cells
Apoptotic cell in liver

25. Apoptosis vs. Necrosis

26. Feature
Necrosis
Apoptosis
Cell size
Enlarged (swelling)
Reduced (shrinkage)
Nucleus
Pyknosis  karyorrhexis  karyolysis
Fragmentation
Cellular contents
Enzymatic digestion; may leak out of cell
Intact, may be released in apoptotic bodies.

27. Feature
Necrosis
Apoptosis
Adjacent inflammation
Frequent No
Physiologic or pathologic role
Always pathologic
Often physiologic, may be pathologic

28. The sequential ultrastructural changes seen in necrosis (left) and apoptosis (right).

29. Good luck