Theme 2 - Genetic and environmental cause of disease: Part 3 Flashcards
What is a myocyte?
muscle cell of heart
If there are pale areas on the heart, what does this mean?
pale areas are where there is irreversible cell injury and cell death
What are 5 cellular adaptions to cell injury?
- hypertrophy- getting larger
- atrophy - shrinking
- necrosis - severe cell swelling and rupture
- apoptosis - internally controlled cell death
- oncosis - pre lethal changes preceding cell death
What are the causes of cell injury?
hypoxia temperature, trauma, radiation chemical agents e.g drugs immunologic reactions infectious agents genetic derangements nutritional imbalances
What are the 3 types of cell injury?
- reversible cell injury
- irreversible cell injury
- ischaemic / reperfusion injury
What is reversible cell injury?
- decrease generation of ATP
- loss of cell membrane integrity
- defects in protein synthesis, and DNA damage
- increased water in cell –> swelling
What is irreversible cell injury?
- severe mitochondrial changes
- extensive damage to plasma membranes
- swelling of lysosomes
- triggers apoptosis and enzymatic degradation of cell
What is ischaemic / reperfusion injury?
new damage on reperfusion mediated by oxygen free radicals
what are the differences between apoptosis and necrosis?
Apoptosis:
- programmed cell suicide
- cellular shrinking
- individual cell deletion
- no inflammatory response
- membrane integrity maintained
Necrosis:
- uncontrolled cell death
- cellular swelling
- many cells affected
- significant inflammation
- loss of membrane integrity
- cell lysis occurs
What is autolysis?
spontaneous lysis of cells and tissues by the release of lysosomal enzymes
What is autophagy?
body’s way of cleaning out damaged cells to regenerate newer, healthier cells
What are the 6 types of necrosis?
- coagulative
- liquefactive
- gangrenous
- caseous
- fat
- fibrinoid
What is coagulative necrosis?
- commonest form (occurs mostly in myocardium)
- caused by ischaemia or infarction e.g MI
- cell architecture preserved
What is liquefactive necrosis?
- seen in brain
- can be caused by bacterial/ fungal infection or CNS hypoxia
- due to lack of supporting stroma, neural tissue may totally liquify
What is gangrenous necrosis?
- putrefaction (decay/rotting) of the tissue
- cause is mostly infectious
- appears black
- 3 types: wet gangrene, dry gangrene, gas gangrene
What is caseous necrosis?
- caused by tuberculosis
- tissue has cheese-like appearance
What is fat necrosis?
-causes: enzymes or trauma
When is fibrinoid necrosis seen?
in malignant hypertension and autoimmune disease
What are the 3 types of cells involved in cell cycle of replication?
- labile cells: excellent regenerative capacity e.g epithelia
- stable cells: good regenerative capacity if needed e.g hepatocytes
- permanent cells: no regenerative capacity e.g neurones
When does liver cirrhosis occur?
- when there is an imbalance in the hepatocyte regeneration and failure to reconstruct the liver architecture
- as the liver is damaged, the connective tissue framework of the liver collapses so regenerated liver cells cannot populate
What is contact inhibition?
cells at edge of defect multiply to cover defect. once these cells cover defect, proliferation stops
What is healing by regeneration?
- tissue returns to normal
- restitution of specialised function
What is healing by repair?
- fibrosis and scarring
- loss of specialised function
- normal structure cannot be replaced
What is organisation?
- the repair of specialised tissue by formation of a fibrous scar
- production of granulation tissue and removal of dead tissue by phagocytosis
- granulation tissue contracts and accumulates collagen, forming a scar
What happens when granulation tissue matures?
- becomes less cellular and less vascular
- has more collagen and ECM is layer down so the wound becomes stronger
What is healing by first intention?
- clean, uninfected surgical would
- fibrin joins sides of wound together
- edges of incision are replaced by collagen
- coagulated blood forms scar
- would closed with sutures
- epidermis grows over defect
- end result is neat scar
What is healing by second intention?
- wound edges not apposed
- Extensive loss of tissue, infection, haematoma
- tissue defect becomes replaced by granulation tissue which eventually contracts, leaving a scar
What condition results in issues with wound healing ?- it is slower and can cause inflammation
diabetes
which local factors inhibit healing?
- infection
- haematoma
- blood supply
- foreign bodies
- mechanical stress e.g broken bone
Which systemic factors inhibit healing?
- age - children heal better than adults
- drugs
- anaemia
- diabetes
- malnutrition
- vitamin C deficiency
What is a keloid scar?
- caused by dermal injury followed by excessive fibroblast proliferation and collagen production
- normally a result of secondary intention
How do fractures heal?
- haemorrhage around bone forms haematoma
- necrotic fragments removed
- osteoblasts lay down
- replacement by more organised lamellar bone
If the brain tissue is injured, why can’t neurones be replaced?
Neurones are terminally differentiated
What is gliosis?
non specific reactive change of glial cells in response to damage to the CNS
occurs after brain damage instead of scarring
Which other type of tissue, except brain cells, cannot fully regenerate?
heart muscle
-damaged heart muscle cannot regenerate, so the heart heals by fibrosis
