[A] 1.38 Necrosis & Apoptosis Flashcards
Give the forms of necrosis
- Death
- Necrosis
- Necrobiosis
- Apoptosis (active process)
Necrosis
Localised irreversible cessation of life in the living organism
- Morphological changes due to enzymatic degradation process in the injured cells
Responses of cells to injury is dependent on…
- Cell type
- Injury type
Give the responses of cells to injury
- Adaptation
- Degeneration
- Cell death
Responses to injuries: Degeneration of the cell may be due to…
- Damage beyond adaptation capacity
- Severe/longlasting injury
- Malnutrition
- Mutation in important cell elements
Stages of cell reaction
- Reversible stage: Can be repaired, normal function returns
- Irreversible stage: “Point of no return” → Cell death
Give the types of cell death
- Physiological
- Passive
- Regulated
- Active
When is physiological cell death seen?
- Embryonic development
- In skin cells & enterocytes
Passive cell death
Necrosis
- The cell stops the vital functions
- Due to stimuli
Regulated cell death
Necrobiosis
Active cell death
Apoptosis
- Elimination of unwanted cell
- “Suicide” of the damaged cell
What can necrosis affect?
- Cell elements
- Single cells
- Tissue parts
- Whole tissues
- Circumscribed areas of organs
- Whole organs
- Body parts
- Damaged tissues
Give the categories of necrosis localisation
- Focal
- Regional
- Multifocal
- Massive
- Zonar
Causes of necrosis
- Acquired - External/Internal
- Genetically programmed
Acquired external necrosis
- Mechanical trauma (Blood vessels)
- Thermal effects (Burns & frostbites)
- Chemical (Acids & bases)
- Coagulation & colliquation of proteins
- Toxins
- Inhibition of enzymes
- Pathogens
Acquired internal necrosis
- Hypoxia
- Ischaemia, hypoxaemia, prestasis, stasis
- Trophoneurotic disorders
- Injury, paralysis of nerves
- Pancreatic enzymes (lipase)
Ultrastructural signs of necrosis
- Ribosomes detach from ER
- Mitochondria and other organelles are swollen
- Membranes are fragmented
- Reduced density of chromatin
Histopathological signs of necrosis
- Nucleus
- Hyperchromatosis of membrane
- Karyopycinosis
- Karyorrhexis
- Karyolysis
- Cytoplasm
- Glycogen disappears
- Increased eosinophilia
- Cytoplasmolysis
Necrosis: Macroscopic changes
- Coagulation necrosis and special forms
- Zenker necrosis
- Caseation
- Liponecrosis
- Colliquation necrosis
Coagulation necrosis
- In the cytoplasm: Protein denaturation
- IC space: Denaturation due to lysosomal enzymes leaving cels
- Nuclear changes
- Occurence:
- Liver, Kidney & spleen
- Causes:
- Bacterial toxins
Pathological signs of coagulation necrosis
- Sharp edges
- Elevated surface
- Dry cut surface
- Driable
- Colour: Dependent on blood content
Special forms of coagulation necrosis
- Zenker necrosis
- Caseation
- Liponecrosis
- Blackleg disease (muscles & clostridia)
Zenker necrosis: Characters
Necrosis of the contractile elements of muscle cells
- Cooked meat-like
- Pale & dry
Zenker necrosis: Causes
- Nutrition
- Se or Vit. E deficiency
- Inproper circulation
- Vasoconstriction
- Improper functional hyperaemia
- Physical effects
- Burns, frost & trauma
Caseation
- Fatty infiltration before necrosis
- Lipochromes stain the necrotic mass
- Tuberculosis & Pseudotuberculosis
Colliquation necrosis
- Enzymatic effect following the disintegration of cells
- Not too much protein
- Necrotic area:
- Pulpy
- Smeary
Colliquation necrosis can be caused by…
Strong alkalic pH
Coagulation necrosis + Secondary colliquation (heterolysis) →
Colliquation necrosis
Give the consequences of necrosis
- Regeneration
- Calcification
- Sequestration
- Cicatrix (organisation)
- Lysis
- Desquamation, erosion & ulceration
- Secondary infection
Apoptosis: Causes
- Physiological:
- Removal of unnecessary cells & tissue homeostasis
- Removal of defective cells (genetic defects)
- Biochemical Effects:
- Activated caspases (cysteine proteases)
- Necrosis: Swollen
- Apoptosis: Shrunken
- Necrosis: Pyknosis → Karyorrhexis → Karyolysis
- Apoptosis: Breaks into fragments
- Necrosis: Damaged
- Apoptosis: Intact, different structure
- Necrosis: Enzymatic lysis, get out of the cell
- Apoptosis: Intact, inside apoptotic bodies
- Necrosis: Often
- Apoptosis: None
- Necrosis: Always pathologic
- Apoptosis:
- Often physiological, elimination of extra cells
- Pathologic after cell damage
