Cell injury Flashcards
What could lead to adaptation of myocytes?
Physiological -exercise
Pathological - high BP
Both of these cause hypertrophy - more myofilaments needed to cope with increased demand of work
What are the two different types of cell injury?
Lethal - will cause death
Sub-lethal ~ produces injury not amounting to cell death
may be reversible or progress to cell death
Describe the the two pathways in which cell injury can occur.
Injured stimulus > cell injury > cell death
Stress > increased demand > inability to adapt > cell injury >cell death
What could lead to cell death in myocytes?
Myocardial infarction
What are the 8 causes of cell injury?
Oxygen deprivation - hypoxia, ischaemia, infarction Chemical agents - drugs Infectious agents - virus, bacteria Immunological reactions - hypersensitivity/`allergies Genetic defects Nutritional imbalances Physical agents - temp, UV light, force Aging
Why can high BP lead to cell injury?
Pathological- body cannot support hypertrophy- if they have high blood pressure- they probably have atherosclerosis too and so body cannot adequately supply the extra oxygen and nutrients- often leading to build up of toxic products which can eventually lead to lethal injury
What are the three things cellular response to injury depends on?
Type of injury
Duration
Severity
What do the consequences of an injurious stimulus on cells depend on?
Type of cell
Cells status
What are the 4 key intracellular systems that are particularly vulnerable to injury?
- Cell membrane integrity
- ATP generation
- Protein synthesis
- Integrity of the genetic apparatus
If a cell cannot synthesise proteins or divide, how does this affect the integrity of the cell?
No protein synthesis
No synthesis of proteins involved in generation of ATP
No cell membrane stability - needed for Na/K+ pumps
Why will ischaemia to the bone have a longer duration to ischaemia of the brain?
It is not metabolically active
What is cellular adaptation?
The ability of cells to respond to various types of stimuli and adverse environmental changes
What is atrophy?
What can it be caused by?
Shrinkage in the size of the cell, loss of cell number too Disuse Atrophy (immobilization after surgery) Denervation injuries (nerves supply nutrients to muscles).
What is hypertrophy?
What can it be caused by?
Increase in size of the cells and consequently the organ
caused by increased functional demand (hypertension) or specific hormonal stimulation (uterus in pregnancy)
Give an example of atrophy.
Cerebral atrophy in dementia
Why are muscles cells more associated with hypertrophy?
Muscle cells can’t divide so to meet demand they must enlarge
What is hyperplasia?
Increase in the number of cells in an organ
What is a physiological example of hyperplasia?
Physiological - in oestrogenic phase the endometrial cells in the uterus increase in number
What is a pathological example of hyperplasia?
Pathological - excessive growth factor or hormomal stimulation, excessive signals to divide can often cause cancer
What is metaplasia?
A reversible change in which one adult cell type is replaced by another
Is metaplasia reversible?
Yes
Give an example physiological metaplasia
During puberty, the cervix will expand, opening the endocervical canal.
This will expose the columnar epithelium to vaginal acid.
The low pH causes the columnar epithelium to transition into squamous epithelium.
Give an example of pathological metaplasia.
Baretts oesophagus, bottom end of oesophagus is exposed to stomach acid and goes from squamous epithelium to columnar epithelium
What is dysplasia?
Precancerous cells which show the genetic and cytological features or malignancy but not invading the underlying tissue
What is a pathological example of dysplasia?
Barrett’s oesophagus that progresses to a dysplastic oesophagus.
What are the key genetic and cytological features of dysplasia that distinguish dysplastic cells from normal cells.
Large nuclei
Increased nuclei to cytoplasm ratio
Increased number of mitoses
What are the two light microscopic changes that can be seen in reversible cell injury?
fatty change - cell can’t metabolise fat
cellular swelling - hypoxia
What is necrosis and what are the four types?
Cell death associated with inflammation Coagulative necrosis Liquefactive necrosis Caseous necrosis Fat necrosis
What is coagulative necrosis and give an example of where it occurs.
Cells are dead- but you can see where they were- keeps its structure and shape but no nuclei are present
Disease Process: Myocardial Infarction
What is liquefactive necrosis and give an example of where it occurs.
Where tissue becomes liquefied - enzymes digest cells
Old cerebral infarct- the brain loses the connective tissue holding it together
What is caseous necrosis and give an example of where it occurs.
Cheesy appearance - often associated with granulomatous disease
Pulmonary TB
What is fat necrosis and give an example of where it occurs.
Dense-blue areas due to white calcium deposit - pancreatic enzymes become active in the pancreas and lipases attack fat in the body
occurs in acute pancreatitis
What is apoptosis?
Programmed cell death, individual cell death, no inflammatory reaction and requires energy
What are the two types of cell death?
Apoptosis
necrosis
What is the main difference between apoptosis and necrosis?
Necrosis - confluent, lots of cells and inflammatory response
Apoptosis - programmed cell death - one cell no inflammatory response
What are the causes of apoptosis?
Embryogenesis
Deletion of auto reactive T cells in the thymus
Hormone-dependent physiological involution
cell deletion in proliferating populations
Mild injurious stimuli that can cause irreparable DNA damage and trigger cell suicide pathways
What is necroptosis and what can cause this?
Programmed cell death associated with inflammation
many causes including viral infections
Define the term ‘biomarker’
In medicine, a biomarker is a measurable indicator of the severity or presence of some disease state
Give an example of a biomarker that clinicians can use to confirm a diagnosis in MI
Myocardial infarction:
Early hypoxic damage will lead to dysfunction of the Na+/K+ pumps.
This will result in cellular swelling and leakage of cell contents.
Troponin and creatine kinases can therefore be used to confirm diagnosis of myocardial infarction.
Why is apoptosis not associated with inflammation?
No cell contents are released to trigger inflammation