Cellular adaptation to stress and toxic injury Flashcards
What is hypoxia?
Insufficient oxygen levels in body tissues
What is ischaemia?
Reduced or restricted blood flow to part of body, which results in hypoxia of that area
How can ischaemia damage cells?
Less oxygen supplied to mitochondria, so less ATP is produced by oxidative phosphorylation, so cell has less energy
What 2 conditions can cause oxygen starvation of tissues?
Anaemia, carbon monoxide poisoning
How can anaemia cause oxygen starvation?
Low healthy RBC count, so less oxygen is carried to tissues
How can carbon monoxide poisoning cause oxygen starvation?
Carbon monoxide displaces oxygen bound to haemoglobin, as CO has a higher affinity for haemoglobin
Give 6 examples of physical agents that damage cells?
Radiation, electric shock, atmospheric pressure changes, temperature extremes, mechanical trauma
Give 3 examples of chemical agents that damage cells?
Alcohol, cyanide, arsenic
Give 4 examples of infectious agents that damage cells?
Viruses, parasites, bacteria, fungi
How can the immune system damage own cells?
Autoimmune diseases attack own cells
Give an example of how genetic abnormalities can damage cells?
Mutation of haemoglobin gene causes sickle cell anaemia
Give 3 examples of nutrition imbalance that damages cells?
Starvation, excess nutrition, vitamin deficiency
What is the general response of normal cells in a stressful environment?
Adapt to undergo reversible injury
What is cellular adaptation?
Reversible changes in size, number, phenotype, metabolic activity, function in response to changes in the environment
Give 4 methods of cellular adaptation?
Hypertrophy, hyperplasia, metaplasia, atrophy
What is hypertrophy?
Increase in the size of cells, resulting in increase in size of affected organ
How do hypertrophic cells increase their size?
Synthesise more intracellular structural components
Why do cells undergo hypertrophy?
They have limited ability to divide, so cannot respond by hyperplasia, as hyperplasia requires cell proliferation to increase organ size
When do muscle cells undergo hypertrophy?
Increased workload
What are the 2 types of hypertrophy?
Pathological, physiological
Give an example of physiological hypertrophy?
uterus size increases in response to pregnancy
Give an example of pathological hypertrophy?
Cardiac muscle size increases due to high bp created by damaged heart valves
What is hyperplasia?
Increase in number of cells by excessive cell division, in an organ/tissue in response to a stimulus
Give 2 types of stimuli that trigger hyperplasia?
Hormones, growth factors
What ability must cells have to undergo hyperplasia?
Ability to divide
Why is hyperplasia a reversible change?
If stimulus is removed, hyperplasia will regress
What are the 2 types of hyperplasia?
Pathological, physiological
Give an example of physiological hyperplasia?
Breast glands undergo hyperplasia to increase milk production
Why does pathological hyperplasia occur?
Inappropriate/excessive action of hormones/growth factors on target cells
How do growth factors stimulate mature cells undergoing pathological hyperplasia?
Mature cells proliferate and stop if growth factors are removed
How do growth factors stimulate stem cells?
Increase output of new cells
Why does endometrial hyperplasia occur, and how does it present in a patient?
Prolonged stimulation of endometrium by oestrogen, presents as abnormal bleeding from uterus
What is endometrial hyperplasia often a precursor of?
Endometrial cancer
What hormone stimulates prostatic hyperplasia in men?
Androgen
What other type of cellular adaptation can hyperplasia occur with?
Hypertrophy
What is metaplasia?
Differentiated cell type is reprogrammed by stem cells into replacement cell type which is better suited to adverse environmental conditions
What condition arises from prolonged metaplastic stimuli, and what type of tissue does it effect?
Dysplasia, which causes disordered growth in epithelium
Is dysplasia reversible?
Potentially reversible if stimulus is removed in dysplasia early stages
If dysplasia continues, what condition can develop?
Invasive carcinoma
What chemical agent is the stimulus of squamous metaplasia in bronchioles?
Cigarette smoke
What nutrition imbalance factor is a stimulus of squamous metaplasia in bronchioles?
Vitamin A deficiency
How does cigarette smoke/Vitamin A deficiency stimulate metaplastic change in bronchioles?
Columnar cells of bronchiole lining are changed into metaplastic squamous cells
What develops from metaplastic squamous epithelium lining bronchioles if the patient keeps smoking?
Disordered growth of metaplastic squamous epithelium develops into invasive squamous cell carcinoma
What stimulates intestinal metaplasia in lower oesophagus?
Acid reflux from stomach
What cells undergo metaplastic change in intestinal metaplasia of lower oesophagus?
Squamous epithelium lining changes into metaplastic goblet cells
What develops from metaplasia of lower oesophagus if the patient keeps having acid reflux?
Invasive adenocarcinoma
What is atrophy?
Reduction in size and number of cells which causes reduction of organ/tissue size
How do cells decrease their size?
Organelles shrink in size
What pathway is activated in atrophy?
Ubiquitin-proteasome pathway
Where does ubiquitin attach to the target protein in the ubiquitin-proteasome pathway in atrophy?
Amino group of side chain of lysine residue
When additional ubiquitins attach to the target protein in the ubiquitin-proteasome pathway, what chain is formed?
Multiubiquitin chain
What is the name of a protein attached to a multiubiquitin chain?
Polyubiquitinated protein
How does autophagy occur in the ubiquitin-proteasome pathway?
Proteasome recognises and degrades the polyubiquitinated protein, which is autophagy as the cell is digesting its own proteins
What are the 2 types of atrophy?
Pathological, physiological
How can bed rest cause disuse atrophy?
lack of movement causes skeletal muscle atrophy, which is a type of disuse atrophy
What bone condition can disuse atrophy cause?
Osteoporosis
How can denervation atrophy affect cell function?
Denervation atrophy damages nerve supply, which affects cell metabolism?
How does chronic low blood supply cause pathological atrophy?
Organ compensates for low blood supply by decreasing cells so that they all have enough oxygen
How can malnutrition cause skeletal muscle atrophy?
When fat is depleted, skeletal muscle is used as nutrition source instead, causes muscle wasting and cachexia (chronic weakening)
Give an example of how loss of endocrine stimulation causes atrophy?
Lack of oestrogen causes atrophy of female genital tract and breast
How can tumours cause pressure atrophy?
Tumour presses and constricts blood supply to tissues
