1. Cell Response to Injury: Morphological Changes 1 Flashcards
stress limit < change = results in what type of damage?
reversible
stress limit > change = results in what type of damage?
irreversible
if cells were static and rigid, what would happen?
they would die
3 ways cells adapt
- increase in cellular activity
- decrease in cellular activity
- alteration of morphology - differentiation
what stimulates increase/decrease cellular activity?
hormonal stimulation
how do cells increase cellular activity?
cells increase in number & size
which type of injury will cause a cell to go from a normal steady state to an altered steady state?
sub-lethal
what occurs to the cell if lethal injury occurs?
goes into the point of no return
in a myocardial infarction, which cells are most sensitive to damage and which are the most robust?
sensitve - cerebral neurones
robus - fibroblasts
3 ways which damage occurs - cellular level.?
- ATP depletion
- Ca2+ influx
- ROS
how does Ca2+ influx cause damage?
an increase in Ca2+ influx causes it to accumulate in the cytoplasm. this activates intracellular enzymes which cause destruction
4 main organelles which are main targets of damaging stimuli
- mitochondria
- cytoskeleton
- cell membrane
- cellular DNA
which type of injury is reversible?
sub-lethal
which type of injury is irreversible?
lethal
what occurs in sub-lethal injury after the removal of the damaging stimuli?
cell recovers
2 causes of lethal injury
- severe damaging stimuli
2. prolonged sublethal damage
3 characteristics of sub-lethal injury
- cell & organelle swelling
- blebbing/irregular PM
- detachment of ribosomes from rough ER
by which process are damaged cell components removed?
autophagy
what is autophagy?
the cell itself phagocytoses its damaged components
2 types of cell death
apoptosis
necrosis
what 2 factors determine type of cell death?
- magnitiude/type of stimulus
2. availability of ATP after the damage
2 types of sub-lethal damage
- cellular swelling/hydropic degeneration
2. fatty change
how can the type of sub-lethal damage be recognised?
light microscope
what 2 things cause cellular swelling/hydropic degeneration ?
- disruption of ionic/fluid homeostasis
2. failure of energy dependent membrane pumps
what types of injury cause fatty change?
hypoxic, toxic, metabolic
how can fatty change be identified histologically?
lipid vaculoes present
in hydropic degneration, explain the steps in which swelling occurs?
- impaired membrane exchange mechanisms (Na/K pump)
- Increased intraceullar Na+
- increased osmosis into the cell
morphology of hydropic degneration
- pale cytoplasm
- vacuolation
- smaller, undefined nuclei
give an example of a toxin which causes fatty change
alcohol
give 2 reasons why lipids accumulate in fatty change
- impaired fatty acid metabolism
2. increased FA synthesis
morphology of fatty change
lipids accumulate in cytoplasmic vacuoles
which cells are affected by the liipid vacuoles? - 3
hepatocytes, cardiac, skeletal cells
how to recognise an affetcted fatty chnage organ?
enlarged and yellow
vacuoles in fatty change can coalesce and form what?
fatty cysts
why do vacuolated lipid cells appear as empty spaces histologically?
the lipids are dissolved during the staining process with alcohol
which stain is used to demonstrate lipids in cells?
sudan black/red
definition of necrosis
denaturation of proteins & enzymatic digestion
4 characteristics of necrosis
- loss of PM
- activated lysosomal enzymes
- enzymatic digestion of cells via autolysis
- leakage of cellular constituents - via inflammation
Necrosis of tissue has distinct patters, why is this important?
gives an idea of the underlying cause
name 6 types of necrosis
- coagulative
- liquefactive
- gangrenous
- caseous
- fat
- fibrinoid
morphology of coagulative necrosis
firm, pale, preserved archictecture and tisse outline
which type of enzymes are broken down in coagulative necrosis?
proteolytic
cause of coagulative necrosis
occlusion of arterial blood supply in kidney and heart
what is liquefactive necrosis?
describes when a tissue is digested and appears as a semi-liquid
what enzymes are involved in liquefactive necrosis?
hydrolytic
common example of liquefactive necrosis
cerebral infarction
how can liquefactive necrosis be identified?
yellow pus - dead leukocytes
why does liquefactive necrosis occur in the brain?
as the neurones have a high lysosomal content - also lack extracellular structural proteins such as reticulin + collagen
causes of liquefactive necrosis
bacterial/fungal infections
how do bacteria/fungi cause liquefactive necrosis?
- enter the body
- attract neutrophils
- neutrophils releases hydrolases which cause liquification
describe the nuclei in liquefactive necrosis
very small - sometimes absent
1st step of gangrenous necrosis after limb losing its blood supply
coagulative necrosis
2nd step of gangrenous necrosis after limb losing its blood supply
bacterial infection can occur - leading to liquefactive necorsis - the leukocytes cause the gangrene
what type of necrosis occurs as a result of TB?
caseous
describe the morphology of caseous necrosis (3)
- cheese like areas - white areas
- fragmented/lysed cells
- granuloma
cause of fat necrosis
pancreatic lipases released into pancreas
what is fat saponification?
where FA combine with Ca2+ to produce white areas
which type of necrosis occurs in the immune reactions of blood vessels?
fibrinoid
what causes the fibrinoid (pink area)
fibrin + ag+ab complex
definition of apoptosis
pathway of cell death induced by a tightly regulated suicide program
describe 5 steps in apoptosis
- cells lose contact with neighboring cells
- activation of enzymes which degrade DNA + proteins
- cytoplasm shrinks
- apoptotic cells break into apoptotic bodies
- bodies phagocytoised by neighoring cells + macrophages
do the cell contents leak out in apoptosis?
no
what do apoptotic bodies express to be identified by the phagocytic cells?
tumour necrosis factor
what is the purpose of apoptosis?
to remove aged, damaged, harmful cells
when disease is present, what does apoptosis aim to do?
remove injured cells which are beyond repair
3 processes where apoptosis is used - NON pathological
- programmed destruction - embryogenesis
- maintain steady cell numbers
- involution of hormone-dependent tissue when not needed
in H+E staining, what would an epidermal apoptotic cell look like?
- intense eosinophillic cytoplasm - bright pink
2. dense disintegreated nuclei
in response to a harmful stimulus, if a cell is able to adapt, what does it do?
change its growth pattern
what is cloudy swelling?
vacuolation - formation of intracellular vacoule
