Cell Tissue Injury and Death Flashcards
Describe labile cells. Give examples.
- Continuously divide and regenerate
- EXAMPLES: Epithelia/haematopietic cells
Describe stable cells. Give examples.
- Low levels of replication and regenerate when signaled
- EXAMPLES: Hepatocytes/endothelial cells
Describe permanent cells. Give examples.
- Unable to proliferate and leave cell cycle
- EXAMPLES: Cardiac muscle fibres, neurones
Outline the cell response to injury.
- Metabolic changes/ischemia cause injury
- Reversible changes occur causing adaptation
- In serious cases, apoptosis and necrosis (IRREVERSIBLE)
What are some causes of cell injury?
- Hypoxia
- Chemical and infectious agents
- Genetic abnormalities
- Immune-mediated processes
What are some targets of cell injury?
- Mitochondria
- Plasma membrane
- Lysosomes
- Nucleus
What are some mechanisms of cell injury?
- Depletion of ATP
- Increased intracellular calcium
- Membrane disruption
- DNA/protein damage
Outline the cellular changes in reversible injury.
- Swelling of ER and mitochondria
- Healing occurs progressively
Outline cellular changes in irreversible injury.
- Swelling of ER and loss of ribosomes
- Myelin figures and membrane blebs form
- Breakdown of plasma membrane and nucleus
- Morphological chanes in nucleus
What are sublethal injuries?
- Injuries that can be compensated for by healing process of cell
Define necrosis.
Cell death due to lethal injury
Outline what occurs during necrosis.
- Depletion of intracellular energy stores
- Disruption of cytoplasmic organelles
- Disintegration of nucleus
- Alterations in ionic transport and increased membrane permeability
Outline the three nuclear changes occurring during necrosis.
PYKNOSIS
KARYORRHEXIS
KARYOLYSIS
Describe pyknosis.
- Condensation of chromatin in the nucleus of a cell
Describe karyorrhexis.
- Fragmentation of nucleus
- Breakup of chromatin into unstructured granules.
Describe karyolysis.
- Dissolution of chromatin of a dying cell due to enzymatic degradation by endonucleases.
Describe coagulative necrosis.
- Most common form of necrosis
- Dead tissue initially swollen and film but later becomes soft
Describe liquefactive necrosis
- Occurs in CNS
- Necrotic neural tissue undergoes liquefaction and glial reaction occurs around periphery, with eventual cyst formation
Describe fat necrosis.
Focal adipose tissue destruction due to
- Direct trauma - release of triglycerides elicting inflammatory response
- Lipolysis - in acute pancreatitis, lipases liberated from damaged acini act on peritoneal fat cells
Describe fibrinoid necrosis.
- Occurs in blood vessel wall
- Eosinophilic and fibrinous deposits are seen
Define caseous necrosis.
- Commonly seen in TB
- Loss of normal tissue architecture replaced by amorphous, granular and eosinophilic tissue
Define gangrenous necrosis
- Dead tissue
- Commonly occurs in lower limbs, GI tract
- Can be dry gangrene - coagulative necrosis pattern/wet gangrene - liquefactive necrosis pattern
Define apoptosis
- Programmed cell death requiring energy input from targeted cells
What are the general steps for apoptosis?
Initiation
Execution
Disposal
Outline the mechanisms of apoptosis.
- INTRINSIC mitochondrial pathway
- EXTRINSIC death receptor pathway
Outline the differences between necrosis and apoptosis. PART 1
- Necrosis occurs on groups of cells/apoptosis occurs on single cells
- Membrane remains intact during apoptosis/necrosis involves loss of membrane integrity
Outline the differences between necrosis and apoptosis. PART 2
- No inflammatory response in apoptosis
- NECROSIS - phagocytosed by neutrophils/macrophages // APOPTOSIS - phagocytosed by neighbouring cells
Define autophagy.
- Degradation of damaged proteins/organelles into constituents
- Occurs with membrane bound vesicles contaning lysosomal enzymes
What are cellular adaptive responses to injury?
- Atrophy
- Hypertrophy
- Hyperplasia
- Metaplasia
