1. 2- Cell Death
Apoptosis
Necrosis

2. Apoptosis
Programmed cell death: plays an important role in many physiological and diseased conditions.
Death of aged cells.
Embryonic remodeling.

3. Human neutrophils are constantly produced in the bone marrow and released into the blood to search for invading pathogens.
After only one day, they "commit suicide" and are replaced by younger cells.

4. The apoptotic neutrophil undergoes a series of changes including violent membrane blebbing, and fragmentation of DNA creating a vacuolar nucleus.
Apoptotic cells shrink in size, break into smaller pieces called apoptotic bodies that are recognized by phagocytes.

5. Membrane blebbing
Cell shrink
Cell fragmentation

6. Morphological changes with apoptosis
shrik
Morphological changes with apoptosis
Membrane blebbing
Cell shrinking.
Cell fragmentation (apoptotic bodies).
Phagocytosis

7. MORPHOLOGY OF NECROSIS

8. Pyknosis Shrunken nucleus with dark staining
Seen in a necrotic (dead) cell

10. Karyorrhexis
Fragmentation of pyknotic nucleus

11. Karyolysis
Extensive hydrolysis of pyknotic nucleus with loss of staining
Represents breakdown of the denatured chromatin

12. Karyolysis

13. Types of Necrosis Coagulative Necrosis Liquefactive Necrosis
Caseous Necrosis
Fat Necrosis
Fibrinoid necrosis
Haemorrhagic Necrosis
Gangrenous Necrosis:
Dry Gangrene: Drying of dead tissue associated with peripheral vascular diseases. Necrosis is separated from viable tissue by line of demarcation.
Wet Gangrene: Coagulative necrosis by ischemia + liquifactive necrosis by superimposed infection.
Gas Gangrene: Gas is produced in necrotic tissue by anaerobic bacteria.

14. 1- Coagulative Necrosis
Dead cells remain as ghost-like remnants of their former self
Classically seen in an Myocardial Infarction
Cardiac muscle fibers
Kidney (necrotic renal tubules)

15. 2- Liquefactive Necrosis
The dead cells undergo extensive autolysis, caused by the release of lysosomal hydrolases (proteinases, DNases, RNases, lipases, etc.)
Seen classically in the spleen and brain following infarction.

16. Liquefactive Necrosis

17. (A) Coagulative vs. (B) Liquefactive Necrosis

18. 3- Caseous Necrosis (Casein - Cheesy)
Resembles cottage cheese
Soft, friable, whitish-grey
Present within infected tissues
Seen in Tuberculosis (Mycobacterium tuberculosis)

19. 4- Fat Necrosis
Leakage of lipases from dead cells attack triglycerides in surrounding fat tissue and generate free fatty acids and calcium soaps
These soaps have a chalky-white appearance
Seen in the pancreas following acute inflammation

20. Causes of cell and tissue necrosis
- Physical agents
- Chemicals and drugs
- Infectious pathogens
- Immunologic reactions
- Genetic mutations
- Nutritional imbalances