2.11 Cell Injury And Fate Flashcards
What are the two types of cell injury?
Sublethal and lethal
What is lethal cell injury?
One that produces cell death
What is sublethal injury?
Produces injury but not amounting to cell death - may be reversible or even progress to cell death
What are 8 causes of cell death?
- Oxygen deprivation
- Chemical agents
- Infectious agents
- Immunological reactions
- Genetic defects
- Nutritional imbalances
- Physical agents eg trauma or rdiation
- Aging
The cellular response to injurious stimuli depends on…
- type of injury
- duration
- severity of injury
The consequences of an injurious stimuli depend on?
- Type of cell
- Cell status
What are 4 intracellular systems which are particularly vulnerable to cell injury?
- Cell membrane integrity
- ATP generation
- Protein synthesis
- Integrity of genetic apparatus
What is meant by atrophy?
Shrinkage in size of a cell / organ by the loss of cell substance
E.g. shrinking brain in dementia patient or muscle atrophy after denervation
What is meant by hypertrophy?
Increase in the size of the cells
What is a pathological example of hypertrophy?
‘Pathological’ cardiac hypertrophy
Thickening of heart muscle, a decrease in the size of the chambers and the reduced capacity of the heart to pump blood
What is an example of physiological hypertrophy?
Increase in the size of cells of the uterus during pregnancy to accomodate for the foetus
What is meant by hyperplasia?
An increase in the number of cells in an organ
What is the main cause of pathological hyperplasia?
Usually due to excessive hormonal or growth factor stimulation
Describe a physiological example where hyperplasia can occur?
Increased oestrogen stimulation drives the increased proliferation of the endometrial glands leading to increased number of endometrial cells
What is a pathological example of hyperplasia?
Carcinoma – too many cells leading to disease
What is metaplasia?
A reversible change in which one adult cell type is replaced by another
Describe a pathological example of metaplasia?
Barretts Oesophagus - The oesophagus is normally lined with squamous epithelial cells, acid reflux causes these to change to columnar epithelial cells
How can metaplasia in barrets oesophagus be reversed?
Taking antacids
Describe a physiological example of metaplasia?
During pregnancy - cervix expands and due to the acid pH of the vagina, the columnar cells lining the internal endocervical canal become squamous
What is meant by dysplasia?
Pre-cancerous cells which show the genetic and cytological features of malignancy but are not invading the underlying tissue
Why do cells undergoing dysplasia appear darker on a slide?
Due to an increased nuclear:cytoplasm ratio
What are the two forms of light microscopic changes associated with reversible injury?
Fatty change and cellular swelling
What is a common cause of fatty change?
Alcohol causes white spots of visible fat in hepatocytes
When you stop drinking, the fat goes away (reversible)
What might be seen on a film on cells undergoing fatty change?
Accumulation of lipids in the cytoplasm – seen on film as large clear droplets filling the cytoplasm
Which condition is fatty hepatic change usually associated with?
Alcoholic liver disease
What is meant by cellular swelling?
When the cytoskeleton of cells are damaged leading to protein accumulation that results in cell swelling
These are degenerative changes (associated with cell and tissue damage)
What are the two features of alcoholic liver disease?
Fatty change and cellular swelling
What is necrosis?
Confluent cell death associated with inflammation
Confluent = layer of cells next to each other
What are the four types of necrosis?
- Coagulative necrosis
- Fatty necrosis
- Liquefactive necrosis
- Caseous necrosis
What is meant by coagulative necrosis?
When the structure of cells becomes fixed after death
E.g. after myocardial infarct
What might muscle cells which have undergone myocardial infarction look like?
Inflammatory reaction to dead muscle cells results in lots of macrophages, but no nuclei as cells are dead
What is liquefactive necrosis?
When the tissue becomes liquefied which results in a transformation of the tissue into a liquid viscous mass
What type of necrosis occurs with cerebral infarction and why?
Liquefactive necrosis as the brain doesn’t have much connective tissue to keep cells in place
What is caseous necrosis?
Tissue maintains a cheese like appearance
What is fat necrosis?
Damage to area of fat occurs and fat is replaced with its oily contents
Which condition is highly associated with fat necrosis?
Acute pancreatitis
Describe the fat necrosis seen in acute pancreatitis?
Pancreatic enzymes are activated in the pancreas rather than the duodenum
Thus, lipases digest pancreatic tissue, and the products bind Ca2+ ions and form salts that deposit in the pancreas
What is apoptosis?
Programmed cell death
What are the five causes of apoptosis? (CHEDI)
Cell deletion in proliferating populations
Hormone-dependent physiological involution
Embryogenesis
Deletion of autoimmune T cells
Irreparable DNA damage
Describe how a cell would undergo apoptosis?
- Cell undergoes injury
- Genetic errors arise from injury
- Attempts are made to repair the error but errors still remain
- Additional injury leads to apoptosis
What are the key differences between apoptosis and necrosis?
Apoptosis can be physiological, necrosis is always pathological
Apoptosis is an active process due to packaging into apoptotic bodies
Necrosis is associated with inflammation, apoptosis isn’t
Apoptosis is at an individual cell level, necrosis involves sheets of cells dying
Necrosis involves losing membrane integrity, apoptosis doesn’t
Why is ATP needed for apoptosis?
ATP is needed to maintain cell membrane integrity and package apoptotic bodies
What are physiological examples of apoptosis?
Elimination of self reactive T cells
What is necropoptosis?
Programmed cell death, associated with inflammation
How does a cell actually die through necrosis?
Enzymatic digestion and leakage of cellular components – cell membrane loses integrity
How does a cell die through apoptosis?
Phagocytosis of apoptotic bodies and fragments
What is a cause of necropoptosis?
Viral infections
