Cell Pathology 4- Cell Injury Flashcards
Describe the two situations that can lead to cell injury
Injurious stimulus
Stress and increased demand above a point where the cells can no longer adapt to the increase in demand.
What happens when cells adapt
They exist in a new equilibrium and homeostasis.
What preceded cell death
Cell injury
What are the two types of cell death
Lethal:
produces cell death
Sublethal:
produces injury not amounting to cell death
may be reversible or progress to cell death
What can we do to sublethal injuries
Reverse the cells to their normal or adapted state.
Limit their progression to cell death.
What are the two types of stress
Physiological- Exercise
Pathological- High Blood Pressure
Both cause hypertrophy- more myofilaments needed to cope with increased demand for work.
What causes a myocardial infarction
muscle death due to ischaemia; atheroma block coronary arteries
What do chemical agents include
Iatrogenic injuries- side-effects of prescribed drugs
What does the mechanism of cell injury depend on
The cellular response to injurious stimuli depends on:
the type of injury,
its duration and
its severity
e.g ischaemia to the bone will have a long duration as bone is not metabolically active. However ischaemia to the brain will have a short duration, we try to mitigate duration in medicine.
What do the consequences of cell injury depend on
on the type of cell
its status
dividing cells are more susceptible to injury- dividing cells in the cervix are more susceptible to damage from HPV.
Which 4 intracellular systems are particularly vulnerable to cell injury
cell membrane integrity,
ATP generation,
protein synthesis and
the integrity of the genetic apparatus
What is fundamental to the existence of the cell
The cell membrane
Describe the interrelationship between these 4 systems
Genetic issues- cannot synthesise proteins or divide. No protein synthesis, no synthesis of proteins involved in generation of ATP- thus no cell membrane stability.
The structural and biochemical components of a cell are so integrally related that multiple secondary effects rapidly occur
Describe the temporal relationship between loss of cell function and cell death
Cellular function is lost before cell death occurs which in turn occurs before the morphological changes are seen
What is meant by atrophy
Shrinkage in the size of the cell (or organ) by the loss of cell substance- loss of cell number too.
When is atrophy pathological
Dementia
Damaged nerves can have atrophic effects on muscle- Muscle atrophy secondary to denervation
What is meant by hypertrophy
Increase in the size of cells and consequently an increase in the size of the organ
What can hypertrophy be caused by
Can be physiological or pathological
It is caused either by increased functional demand or specific hormonal stimulation
Hormones- overproduction of TSH- increases size of follicular cells in thyroid gland.
Physiological; e.g. Uterus in pregnancy increases in size
Pathological- associated with disease state; e.g. Increased demand leads to hypertrophy
What is a key characteristic of muscle
They rarely divide- thus when the demand is increased they get bigger.
Define Hyperplasia
An increase in the number of cells in an organ.
Describe the causes of hyperplasia
Can be physiological or pathological
Physiological hyperplasia can be either hormonal or compensatory
Pathological hyperplasia is usually due to excessive hormonal or growth factor stimulation
Physiological; with every menstrual cycle, endometrial cells increase in number and in breasts during oestrogenic phase - hormones very important- hypertrophy also occurs here- increased TSH also causes hyperplasia of follicular cells.
Pathological- carcinomas.
Define metaplasia
A reversible change in which one adult cell type is replaced by another
What are the causes of metaplasia
May be physiological / pathological
Pathological- smoking changes epithelium from columnar to squamous- if you stop smoking it will reverse.
Physiological- puberty- cervix expands- opens canal- columnar exposed to acid- squamous- pregnancy reverses this
Pathological; Barrett’s oesophagus - in acid reflux, normal stratified squamous epithelia metaplase to columnar due to acid, but reversible if stop acid production as will become stratified squamous again.
Define dysplasia
Precancerous cells which show the genetic and cytological features or malignancy but not invading the underlying tissue
