Cell death Flashcards
Name the 2 concurrent processes which cause necrosis
- Enzymatic digestion of the cell
- Denaturation of proteins
What is necrosis?
Morphological changes that follow cell death
Define the following:
- Autolysis
2. Heterolysis
- Lysosomal enzymes of the dying cell itself
2. Enzymes from infiltrating leukocytes
Describe the morphological features of necrotic cells
- Increased eosinophilia
- Pyknosis = nuclear shrinkage
- Fragmentation of the pyknotic nucleus
Which type of necrosis is being described?
- Dominant feature = denaturation of proteins
- In hypoxic cell death
- Preservation of cell outline
Coagulative necrosis
Describe liquefactive necrosis
- Dominant feature = enzymatic digestion
- With focal bacteria and fungal infections
- Complete digestion of cells to liquid mass
Which type of necrosis is being described?
- Complete obliteration of tissue architecture
- Surrounded by distinctive inflammatory cell border
Caseous necrosis
Describe fat necrosis
Focal destruction of adipose tissue
Due to release of pancreatic enzymes
Fatty acids combine with calcium -> visible white chalky areas
What is apoptosis?
Programmed cell death to eliminate host cells
What are the morphological features of apoptosis?
- Cell shrinkage
- Chromatin condensation
- Phagocytosis of apoptotic cells
What are some biological features of apoptosis?
- protein cleavage
- protein cross-linking
- DNA breakdown
- phagocytic recognition
Describe the initiation stage of apoptosis
- By apoptotic stimuli
- Signals are transmitted across the plasma membrane to intracellular regulatory molecules
- Signals address targets within cells e.g. glucocorticoids, heat, viral infections
What is able to suppress apoptosis?
- hormones
- growth factors
- cytokines
What is able to activate apoptosis?
- Receptor ligand interaction
What is the ultimate outcome of pro-apoptotic signals?
Cytochrome C release from mitochondria -> caspase cascade
What occurs in the execution phase of apoptosis?
- Mediated by caspases
- Functional division into initiator and execution caspases
- Disruption of cytoskeleton
- Destruction of nuclear proteins
Compare the histological changes in necrosis and apoptosis
Necrosis:
- Whole fields of cells affected
- Loss of cell borders with irregular fragmentation
- Swelling and loss of surface structures
Apoptosis:
- Individual cells affected
- Formation of round bodies
- Chromatin condensation
- Preservation of internal and external membranes
Describe phagocytosis in apoptosis
- No release of pro-inflammatory breakdown products
- Ingestion by adjacent cells or tissue macrophages
- No scarring
What is activation induced cell death?
Activated T-cells express enhanced levels of surface molecules that invoke apoptosis in a process of activation-induced cell death
Out of necrosis and apoptosis, which involves inflammation?
Necrosis
What happens to the cell size during:
- necrosis
- apoptosis
- Enlarged, swelling
2. Reduced, shrinkage
Name the 3 steps that happen to the nucleus in necrosis
- Pyknosis
- Karyorrhexis
- Karyolysis
