Cell injury, response and adaptations Flashcards
What are internal injurious stimuli?
- Oxygen deprivation
- Nutritional imbalance
- Immune system reactions
- Genetic abnormalities
- Ageing
- Workload imbalance
What are external injurious stimuli?
- Infectious agents
- Physical agents
- Chemicals, drugs & toxins
What is atrophy?
decrease in size
What is hypertrophy?
increase in cell size due to increased number and size or organelles
What is dysplasia?
reversible/partial reversible change categorised by disorder growth
What is hyperplasia?
An increase in the number of parenchymal cells in an organ or tissue
What is metaplasia?
Change from the normal cell type to another type that is better able to withstand the insult/stress
What are the 4 main mechanisms for cell injury?
-impaired ATP production
-impaired cell membrane function
-biochemical pathway derangement
-DNA damage
What may cause mitochondrial damage/ dysfunction?
- damage to mitochondrial membranes
- increased cytosolic calcium
What can cause impaired ATP production?
Hypoxia caused by
- Respiratory failure
- Cardiac failure
- Reduced vascular perfusion (ischaemia
- Anemia
- Severe blood loss
What are the effects of impaired ATP production?
- Sodium potassium ATPase pump failure (as requires ATP)
- Sodium increases inside cell, water follows, cells burst
- Switch to anaerobic metabolism, lactic acid buildup
- Enzyme denaturing
- Altered protein metabolism
- As require energy, and if pH also low, denature of proteins
- Increased cytosolic calcium
- Calcium ATP-ase pump failure
Increased intracellular calcium
What are the effects of increased intracellular calcium on cells?
- Activates cellular enzymes eg protease, damaging membranes
- Eg mitochondrial membrane
- Leading to apoptosis (programmed cell death) or release of free radicals
- Lipid peroxidation of membranes occurs
- Chain reaction
- Degrades lipid membrane
What are the consequences of membrane damage?
- Mitochondrial dysfunction
- Plasma membrane dysfunction,
- Leakage of lysosomal enzymes into cytosol
How do free radicals effect the plasma membrane?
attack and cause lipid peroxidation
What causes cell swelling?
- Hypoxia
- (As ATP not produced so no ATPase so Na+ builds up so cell swells via osmosis)
- Cell membrane damage by free radicals
- Cell membrane injury by penetration of transmembrane complexes by eg bacterial toxins
- Cell membrane damage by toxins inactivating ion channels or pumps
What can cause cellular hydropic degeneration?
Increased intracellular sodium and water decreased potassium
What can cause excess lipid accumulation?
excessive delivery and uptake of lipids
reduced metabolism of lipids in hepatocytes
reduced export of lipids from the hepatocyte
What is the histological appearance of lipid accumulation and hydropic change in cells?
lipid accumulation - clear vacuoles in the cell
hydropic - clear spaces but from the dilation of organelles.
What are gross evidance of lipid accumulation and hydropic on organs?
lipids - enlarged organs presenting with yellow-brown colour and a greasy texture
hydropic - organs are enlarged but a paler colour
What are the microscopic features of necrosis
- Karyolysis - dissolution of the nucleus
- Pyknosis - nuclear condensation (chromatin clumping
- Karyorrhexis
What is coagulative necrosis
Caused by hypoxia
Tissue looks pale and is surrounded by red areas
What is dry gangrene
extremities, initial coagulative necrosis before it dehydrates and shrivels
What is fat necrosis
adipose where fat is white, chalky appearance.
What is liquedative necrosis
occurs in CNS from hypoxia injury - forms semi-liqued
associated with pus forming organisms
What is wet gangrene
necrosis by coagulative before it is invaded by saprophytic bacteria which liquifies the dead tissue
What is Caseous necrosis
Associated with infectious agents (tuberculosis commonly) soft and granular, like cottage cheese
What is the difference between metastatic and dystrophic calcification
Dystrophic calcification - occurs in sites of necrosis
Metastatic calcification - disturbed calcium metabolism resulting from hypercalcaemia and deposition if calcium salts in tissues
How are the 3 types of jaundice caused
- Prehepatic icterus - excessive bilirubin production due to haemolysis
- Hepatic Icterus - hepatocyte damage and decreased metabolism of bilirubin
- Posthepatic (obstructive) icterus - obstruction of bile excretion (tumour)
What is amaloydosis?
Extracellular deposition of proteins
- pushes apart the cells in a tissue
- commonly caused with chronic inflam/infect
less commonly associated with plasma disorder
