Cell Injury, Death And Adaptation Flashcards
Implicated for accelerated proteolysis in catabolic conditions (cachexia in CA, TB)
Drives atrophy by decreasing cell size
Posted in intermediate filaments of cytoskeleton
Proteasome recognizes and tags them for degradation
Ubiquitin Proteosome Pathway
REVERSIBLE change in which one adult cell type (epi or mesen) is replaced by another adult
Metaplasia
Replacement better able to withstand environment
Metaplasia occurs by
reprogramming stem cells to differentiate along a different pathway vs phenotypic transdifferentiation change
But inc propensity for malignant transformation
Inc cell and organ size in resp to inc workload in cells incapable of cell division
Hypertrophy
Hypertrophy esp in cardiac tissue are induced by
1) mechanical trigger
2) trophic chemical trigger
Inc cell number in response to 1) hormone 2)compensation
in cells with abundant tissue stem cells
Hyperplasia
Dec cell organ and size due to dec nutrient and disuse
Inc protein degradation dec protein synthesis
Atrophy
First lost after stress and noxious influence in the cell
Cellular function
Lag with morphologic change and cell death
Irreversibility in cell damage occurs (2)
1) inability to correct mitochondrial dysfunction (lack of oxphos and ATP generation) despite resolution
2) profound disturbance in membrane function
targetting membrane of this organelle promotes progression to necrosis
Lysosome
Enzymatic dissolution by hydrolases
Barbiturates cause tolerance in the long run bec
Hypertrophy of ER and inc CYP450 activity in liver
Morphologic changes in reversible injury (2)
Cellular swelling
Fatty change
Small clear vacuoles within cytoplasm which pinched off from SER
Hydrophic change
Vacuolar degeneration
Failure of energy dependent ion pumps in plasma mem leading to inability to maintain ionic and fluid homeostasis
Cellular swelling
Occurs in hypoxic injury, toxic or metabolic charac by appearance of lipid vacuoles in cytoplasm
Fatty change
Intracellular changes assoc with reversible injury (4)
1 plasma membrane blebbing and loss of microvilli
2 mitochondrial swelling
3 dilation of ER
4 eosinophilia due to dec cytoplasmic RNA, nuclear alteration chromatin clumping
Loss of basophilia of chromatin in necrotic cell
Karyolysis
due to DNase
Nuclear shrinkage and inc basophilia in necrotic cells
Pyknosis
Fragmentation of pyknotic nucleus in necrotic cell
Karyorrhexis
Necrotic cells become calcified by
Necrotic cell -> myelin figure -> degraded to fatty acid -> FA with calcium salt -> calcified
Architecture preserved with tissues having firm texture
Structural proteins and enzymes denatured halting proteolysis of dead cell
Infarcts, solid organs
Coagulative necrosis
Focal bacterial, fungal infection stimulating leukocytic digestion of tissue
Completely digested -> liquid viscous mass
Creamy yellow pus
Brain
Liquefactive necrosis
Limb losing blood supply undergoing coagulative necrosis
Bacterial superimposition -> coagulative necrosis (modified)
Gangrenous necrosis
Wet gangrene
Cheese like friable yellow like
Collection of lysed cell with pink appearance complete obliteration of architecture
Enclosed in an inflammatory border
Focus of inflammation:
Caseous necrosis
Granuloma
Focal areas of fat destruction resulting from release of pancreatic lipase liquefying fat cells
FA combine with Ca to form chalky white areas (saponification)
Fat necrosis
Deposition of immune complex with fibrin in walls of arteries producing :
Seen in PAN
Fibrinoid
Inc eosinophilia
Nuclear shrinkage, fragmentation, dissolution (pyknosis, karyorrhexis, karyolysis)
Breakdown of plasma and organelle membrane
Abundant myelin
Leakage and digestion of enzyme to cell content
Necrosis
Principal targets and biochem mech of cell injury (4)
1) mitochondria (ATP and ROS generation)
2) calcium homeostasis disturbance
3) plasma and lysosomal membrane damage
4) DNA damage and protein misfolding
Restoring of blood flow to ischemic but viable tissue results in death of cells undergoing irreversible injury
Ischemia-reperfusion injury
Ischemia reperfusion injury occurs due to (2)
Generation of ROS
Inflammation bec of influx of leukocytes and plasma protein and complement
Cell death where cells activate enzymes that degrade its own nucleur DNA and cytoplasmic proteins
Apoptosis
Apoptosis does not elicit inflammatory response bec
Membranes remain intact and fragments are cleared before contents have leaked
Apoptosis is induced in pathologic conditions (4) by
1) DNA damage
2) misfolded protein accumulation
3) cell injury in infection
4) Pathologic atrophy
Reduced cell size
Fragmentation into nucleosome
Intact altered structure and orientation of lipid
Intact cellular contents released into apoptotic bodies
No inflammation
Apoptosis
Cysteine proteins that cleave proteins after aspartic residues activated in apoptosis
Caspases
Survival and death of cell depends on
Permeability of mitochondria
Permeability of mitochondria is controlled by
20 proteins prototype BLC 2
Apoptosis mitochondrial pathway
Lack of survival signals (DNA damage, protein misfolding) -> activation of sensors Bax and Bak channels inhibiting BCL-2 -> leak of cytochrome c and proteins -> capsase activation
Loss of CFTE leading to defect in chloride transport
Cystic fibrosis
Loss of LDL receptor leading to hyperchole
Familial hypercholesterolinemia