Cell injury Flashcards
What are the 8 causes of cell injury?
Oxygen Deprivation Chemical Agents Infectious Agents Immunological Reactions Genetic Defects Nutritional Imbalances Physical Agents Ageing
What is lethal and sub-lethal?
lethal - causes cell death
sub-lethal - causes injury but may progress to death
What three things does the cellular response to injury depend upon?
- the type of injury
- the duration
- the severity
What 4 things does the consequence of an injury depend on?
- the type of cell (e.g. brain more sensitive to ischaema)
- status (dividing cells more affected)
- adaptability
- genetic makeup
Which 4 intracellular mechanisms are vulnerable to injury?
- Cell membrane integrity
- ATP generation - important in maintaining cell integrity
- Protein synthesis - affect cell membrane
- Integrity of the genetic apparatus
Why is the cell membrane so important?
The cell membrane has proteins which distinguish self from non-self so once you break this functionality you get problems
Do cell always die before they stop working?
No, cells stop working before they die so loss of function could kill before morphological changes take place in the cell.
E.g. ventricular fibrillation - heart stops working and you die but you may not see anything at post mortem.
What is atrophy?
Shrinking in the size of the cell or organ by the loss of cell substance
What is hypertrophy and what may cause it?
Increase in the size of cells and, consequently, an increase in the size of the organ
Can be caused by increased functional demand or specific hormonal stimulation
What is hyperplasia?
Increase in the number of cells in an organ
What are the causes of hyperplasia?
Can be physiological or pathological
Physiological Hyperplasia: hormonal or compensatory
- Hormonal - oestrogenic wave of proliferation of the endometrium
- Compensatory - if some tissue is lost
Cancer is pathological hyperplasia
What is metaplasia and give an example?
A reversible change in which one adult cell type is replaced by anotherm
E.g. Barrett’s esophagus - instead of squamous lined epithelium you get columnar epithelium
It can be physiological (cervix) or pathological (oesophagus)
What is dysplasia?
Precancerous cells which show the genetic and cytological features of malignancy but not invading the underlying tissue.
What are the light microscopic changes involved with reversible injuries?
Fatty change
Cellular swelling
These are examples of degenerative changes - associated with cell and tissue damage. Holes in the liver is due to fat accumulation due to alcohol consumption. Ballooning is also associated with alcohol
Both of these changes are reversible.
What is necrosis?
Confluent cell death associated with inflammation - areas of cells die
What are the four types of necrosis?
Coagulative Necrosis
Liquefactive Necrosis
Caseous Necrosis
Fat Necrosis
Coagulative necrosis
Cell death occurs but they are still recognizable as cells, they maintain cellular architecture e.g. myocardial
infarction
Liquefactive necrosis
The tissue become liquefied and cells can only be identified by nearby tissue e.g. in the brain.
What are some changes indicating irreversible damage to nuclei?
- lysed nuclei
- fragmented nuclei
- shrunken nuclei
What is caseous necrosis?
‘Cheesy’ necrosis - associated with pulmonary TB
The necrotic area is granular which makes it caseous.
What is fat necrosis?
Acute pancreatitis - you get release of lipases which digests the fat and hydrolyses triglycerides to free fatty acids and glycerol.
The free fatty acids combine with calcium in the extracellular fluid and deposits. Each of the deposits (white parts) are areas of fat necrosis
Fat necrosis could be due to sufficiently severe fat trauma but it is classically associated with acute pancreatitis.
What is an ulcer?
A local defect, or excavation of the surface, of an organ or tissue, produced by sloughing (removing a layer) of necrotic inflammatory tissue
What is apoptosis and its features?
Programmed cell death of single cells. The nucleus shrinks and little bits of the cell break off (lined by cytoplasm). Small vesicles form and they are then phagocytosed by macrophages
- Not associated with inflammation
- It is active cell death - energy is used to die
- Necrosis is associated with being pathological
- Apoptosis can be physiological or pathological
- Apoptosis is a neat process as cell membrane doesn’t rupture and no inflammation
Nothing from inside the cell is exposed to the outside - so there is no inflammation.
Compare apoptosis and necrosis
- Apoptosis is mot associated with inflammation
- Apoptosis is active cell death - energy is used to die
- Necrosis is associated with being pathological
- Apoptosis can be physiological or pathological
- Apoptosis is a neater process
