Pathology: Necrosis and Apoptosis Flashcards
Define hypertrophy
An increase in cell size
Define hyperplasia
An increase in cell numbers
Define atrophy
Reduction in cell size
Define hypoplasia
A below-normal number of cells
What factors overwhelm cell stress coping mechanisms such as hyperplasia and hypertrophy?
- Rapidity of stress
- Quantity of stress
What are the 2 possible outcomes of the cell stress coping mechanisms being overwhelmed?
- Apoptosis
- Necrosis
Describe necrosis
- Requires no energy
- Always pathological
- Uncontrolled cell death
List the types of necrosis
- Coagulative necrosis
- Liquefactive necrosis
- Caseous necrosis
Describe coagulative necrosis
- The cell outline is preserved
- So the tissue still has some structure
- Common with hypoxic, ischemic/infarction injury
- Cells are consumed by enzymes
- Doesn’t occur in the brain
- Cell is NOT destroyed by proteolysis via its enzymes
What kinds of injury commonly causes coagulative necrosis?
- Hypoxic
- Ischemic, infarctions
Describe liquefactive necrosis
- Cells form a liquid (no cell structure remains)
- Pus
- Associated with localised bacterial/fungal infections
- Brain necrosis is liquefactive
- After/if pus clears leaves a cavity
Describe caseous necrosis
- Cheesy necrosis
- Granulomatous inflammation with central necrosis
- Associated with TB
Define apoptosis
Programmed cell death in response to specific signals
Describe apoptosis
- Requires energy
- Can be physiological or pathological
- Can be triggered by intrinsic or extrinsic factors
- Mechanism relies on caspase cascade
Give examples of pathological apoptosis
- Some autoimmune disorders
- Infective disease
- Cancer
- In response to trauma
Give an example of physiological apoptisis
- Growth and development
e. g. finger development - Removal of self-reactive lymphocytes
- Involution of the uterus
Describe the extrinsic pathway for apoptosis
- Initiated by the activation of an death receptor (Fas or TNFR)
- The fas receptor is activated by a fas ligand on another cell (often a type of T-Lymphocyte)
OR - The TNF receptor (TNFR) can is activated by TNF
- Both mechanisms are mediated by fas associated death domain (FADD)
- Causes a caspase cascade
Describe the mitochondrial mechanism for the intrinsic pathway for apoptosis
- Normally cell survival signals promote anti-apoptotic molecules in the mitochondrial membrane
- These inhibit Bax, Bak
- When the signals stop the Bax is free to form channels in the membrane allowing the contents to escape
- Cytochrome C escapes
Describe the role p53 plays in apoptosis
- Involved at cell cycle checkpoints
- Checks for errors in DNA
- If error found, repair is attempted
- If it fails then apoptosis is induced
List the risks of not having enough apoptosis
- Cancer
- Autoimmune disease
List the risks of having too much apoptosis
- Neurodegenerative disorders
-
Describe the morphological changes that occur during apoptosis
- Cell shrinks
- Pyknosis (irreversible chromatin condensation)
- Nucleus breaks up
- Apoptotic blebs form
- Apoptotic bodies (blebs after they break off)
What cell type phagocytose apoptotic bodies?
Macrophages
What are the causes of cellular aging
- Oxidative stress
- Accumulation of metabolic by-products
