Pathology Flashcards
What are the 2 types of autopsy? Describe them.
hospital: audit, research, teaching, governance
medico-legal: 90% of autopsies, either coronial or forensic
What are the 3 types of death?
presumed natural: unknown/not seen by doctor in last 14 days
presumed iatrogenic: because of their care eg postoperative, anaesthetic, abortion
presumed unnatural: accidents, unlawful, suicide
What happens in an autopsy?
history -> external exam -> evisceration -> internal exam -> reconstruction
How does inflammation appear? (5 things)
- redness: vessel dilation
- heat: increased blood flow = vessel dilation/systemic fever
- swelling: oedema/mass of infl cells/formation of new connective tissue
- pain: stretching of tissue due to pus + oedema/chem mediators eg bradykinin
- loss of function
When is inflammation good?
infection
injury
When is inflammation bad?
autoimmunity
over-reaction to stimulus
What are the features of acute inflammation?
sudden onset
short
usually resolves
involves neutrophil polymorphs
What are the features of chronic inflammation?
slow onset/sequel to acute
long
may never resolve
involves lymphocytes and macrophages
How are neutrophil polymorphs involved in inflammation?
short lived first on scene die at scene + produce pus release chemicals to attract other infl cells phagocytosis
How are macrophages involved in inflammation?
last weeks to months
phagocytic: ingets debris
don’t always die: carry debris away or present antigens to lymphocytes
eg Kupffer cells (name depends on location)
How are lymphocytes involved in inflammation?
last years
produces chemicals to attract other infl cells
immunological memory
How are fibroblasts involved in inflammation?
long lived
form collagen = scarring
How are endothelial cells involved in inflammation?
line capillary vessels
become sticky so infl cells adhere to them
become porous so infl cells can pass to tissues
grow into areas of damage = new capillaries
What are granulomas?
type of chronic inflammation
epitheliod = group of pale macrophages surrounded by lymphocytes
What is the treatment for inflammation?
NSAIDs eg aspiring, ibuprofen
steroid cream for skin rash eg betnovate
How do corticosteroids work?
bind to DNA
up regulate inflammatory inhibitors
down regulate chemical mediators of inflammation
How does inflammatory treatment work?
inhibit prostaglandin synthetase
prostaglandin is a chemical mediator of inflammation
What are the 5 causes of acute inflammation?
microbial infections hypersensitivity physical agents eg UV, cold chemicals tissue necrosis
What is cellulitis?
skin infection due to vascular dilation in acute inflammation = red, hot skin
What are the 3 main stages of acute inflammation?
- changes in vessel calibre + flow
- increase in vascular permeability + formation of fluid exudate
- formation of cellular exudate: neutrophil polymorphs move into EVS
What chemical mediators are released in acute inflammation?
histamine + thrombin: create very firm neutrophil adhesion to endothelial surface
What do chemical mediators cause in the acute inflammation process?
vasodilation emigration of neutrophils chemotaxis increased vascular permeability itching and pain
What are the harmful effects of acute inflammation?
digestion of normal tissue
swelling
inappropriate response
What are the 4 outcomes of acute inflammation?
resolution
suppuration
organisation
chronic inflammation
What is resolution in acute inflammation?
usual process: restoration back to normal
happens in: minimal cell death, an organ able to regenerate, rapid destruction of cause, rapid removal of fluid by vascular drainage
eg acute lobar pneumonia
What is suppuration in acute inflammation?
occurs due to excessive exudate
formation of pus, neutrophils + bacteria, cellular debris and liquid globules
persistent and usually infective agent
abscess will heal, form granulation and then scar = organisation
What is a collection of pus called?
abcess
What is organisation in acute inflammation?
due to excessive necrosis
replacement of tissues by granulation tissue
happens when: lots of fibrin which can’t be removed, lots of necrotic tissue, exudate/debris can’t be digested
What is the process of organisation in acute inflammation?
new capillaries grow into exudate macrophages migrate fibroblasts proliferare fibrosis scar
Why does acute inflammation lead to chronic?
persistent cause
Which 2 outcomes of acute inflammation lead to fibrosis?
chronic inflammation
organisation
What are the systemic effects of acute inflammation?
pyrexia weight loss amyloidosis hyperplasia of reticuloendothelial system haematological changes
Which cells predominate in chronic inflammation?
lymphocytes plasma cells macrophages giant cells fibroblasts
What are the main causes of chronic inflammation?
primary cause
transplant rejection
progression from acute inflammation
recurrent episodes of acute inflammation
What is the main complication of chronic inflammation?
amyloidosis
Give some examples of a cause of chronic inflammation?
infective agent: TB, leprosy
exogenous materials: sutures
primary granulomatous diseases: Crohn’s
What are the stages of connective tissue proliferation?
- angiogenesis
- fibroblast proliferation and collagen synthesis
= granulation tissue
(regulated by growth factors)
What are the 2 lymphocytes involved in inflammation?
B: contact with antigen = form plasma cells = produce antibodies
T: cell-mediated immunity, produce cytokines = recruitment, activation
Where does acute inflammation occur in disease?
after an acute MI
complications of an MI
atherosclerosis
Where does chronic inflammation occur in disease?
cancer
myocardial fibrosis after MI
neurodegenerative diseases eg MS
atheroclerosis
What is resolution?
initiating factor is removed = tissue is undamaged and able to regenerate
What is repair?
initiating factor is present = tissue damaged and unable to regenerate
What is organisation?
repair of specialised tissue by the formation of a fibrous scar
What happens after hepatocyte loss in the liver?
complete restitution
What happens after the hepatic architecture is damaged in the liver?
cannot be regenerated
only regenerate on hepatocyte loss
When does cirrhosis occur in the liver?
when there is an imbalance between hepatocyte regeneration and failure tor reconstruct the hepatic architecture
When does complete restitution occur?
when there is a loss of a labile cell population that can be completely restored eg skin abrasion
What happens when the lungs are damaged?
as long as the structure isn’t damaged, pneumocytes will regenerate
Why do skin abrasions heal so quickly?
not all the epithelium is removed
hair follicles and sweat glands remain
only the small vessels are occluded by thrombosis
What happens in 1st intention healing of the skin in an incised wound?
cut through all layers of the skin
cut fills with fibrin from the blood = weak and rapid fibrin joint
coagulated blood forms a scab
fibroblasts bring collagen forming a white scar = strong collagen joint
capillaries proliferate
What happens in 2nd intention healing of the skin?
deep cut with no sutures/tissue loss
fills with capillaries and fibroblasts that produce collagen
phagocytosis occurs to remove debris
granulation tissue forms
epithelial regeneration occurs to cover surface
What is the difference between 1st and 2nd intention repair of the skin?
2nd is slower and forms a bigger scar than if sutured
What is the process of repair?
damaged tissue is replaced by fibrous tissue
collagen produced by fibroblasts
eg after MI, CI, spinal cord trauma
Which cells do regenerate?
hepatocytes pneumocytes all blood cells gut epithelium skin epithelium (if in right place) osteocytes
Which do NOT regenerate?
myocardial cells
neurones
What happens in organisation?
tissue contracts
accumulates collagen to forma a scar
remodelling occurs
How does granulation tissue form?
capillary endothelial cells proliferate into loops and grow into damaged area
fibroblasts stimulated to divide and secrete collagen
(acquire myofibroblasts for collagen and wound contraction)
capillary loops + myofibroblasts = granulation
How does a thrombus form?
- endothelial cell injury
- collagen exposed: platelets stick to collagen and each other
- release platelet aggregating factor = more platelets (positive feedback)
- triggers clotting cascade
- disrupted laminar flow means rbc are also trapped - platelet aggregation = thrombus formation
- chemicals cause fibrinogen to polymerise to fibrin
- fibrin is deposited forming a mesh which traps rbcs
- fibrin increases its own polymerisation (positive feedback)
What is a thrombus?
solidification of blood contents that forms WITHIN the vascular system during LIFE
What’s the difference between a thrombus and a clot?
a clot forms outside the vascular system or after death
What are the 3 main reasons a thrombus forms?
- change in vessel wall eg endo cell damage
- change in blood flow
- change in blood constituents
How is a thrombus usually prevented?
- laminar flow: cells flow in the centre of the artery and don’t touch the sides
- endo cells aren’t sticky when they are healthy
How do venous thrombi differ to arterial thrombi?
slower due to slower flow and contraction of surrounding muscles
Why are venous thrombi a big problem in hospitals?
lying down too often: cells hit the endothelium due to a slow flow = endothelial cell injury
What can a venous thrombi lead to?
pulmonary embolism
Where do venous thrombi most commonly form?
at valves
What types of granules are platelets made up of?
alpha: platelet adhesion to damaged wall, contains fibrin, fibrinogen, PGF
beta: platelet aggregation, contains ADP
How are platelets involved in the formation of a thrombus?
- platelets activated + granule contents released on contact with collagen
- change shape + extend pseudopodia
- forms a mass over the damage until the endothelial cells have regenerated
- if this starts in an intact vessel = thrombus
What are the clinical effects of an arterial thrombus?
loss of pulse distal to injury
area is cold, pale + painful
tissue dies + leads to gangrene
What are the clinical effects of a venous thrombus?
area tender due to ischaemia
reddened as it can’t be drained by the veins
swollen
What are the 4 possible outcomes of a thrombus?
- lysis + resolution (body dissolves it away)
- organisation (invasion of macrophages and fibroblasts - can cause narrowing)
- recanalisation (intimal cells proliferate and small capillaries grow into the thrombus - fuse to make larger vessels - recanalised - functional again)
- embolism (infarction)
What are some preventative methods to a thrombus?
aspirin: prevents platelet aggregation at low doses, prevents them being sticky
warfarin: used in severe cases, inhibits vitamin K
exercise
elastic stockings
What is an embolus?
mass of material in the vascular system able to lodge in a vessel and block it
What are the causes of an embolus?
most common: piece of thrombus broken off
air: IV fluids/bloods
cholesterol crystals: from atheromatous plaque
fat: severe trauma with multiple fractures
How does a venous embolism occur?
venous system - vena cava - right side of heart - pulmonary arteries - pulmonary embolism
Why can’t a venous embolism reach the arterial circulation?
lungs split down into capillary size so act as a filter for venous emboli
What happens to small venous emboli?
unnoticed
or are organised (scar = some narrowing)
What are the effects of a bigger emboli?
respiratory and cardiac problems: chest pain and shortness of breath
may become infarcted and increase the risk of another emboli
What are the effects of a massive emboli?
sudden death
usually from leg veins and travel to the bifurcation of the pulmonary arteries
Where do arterial emboli originate?
heart
atheromatous plaque
Where can an arterial emboli travel to?
from heart: anywhere
from cholesterol crystals: lower limbs + renal arteries
Why do arterial emboli form in the heart?
after a MI
atrial fibrillation
What is ischaemia?
reduction in blood flow to a tissue due to constriction/blockage of vessel supplying it
Which cells are most susceptible to ischaemia?
cells furthest from the vessel
still don’t necessarily die
Ischaemic damage is reversible depending on?
duration of ischaemia
metabolic demands of tissue (heart and brain most vulnerable)
What is infarction?
death of ells due to an obstructed artery (type of ischaemia)
usually caused by a thrombus
What factors increases the susceptibility of an infarction?
- most organs have a single artery supply (end arterial supply)
- watershed areas: at limits of 2 different blood supplies (occurs at a decrease in BP)
- portal vasculature: organs where blood as already passed through 1 set of capillaries (decreases IV pressure = decreases oxygen saturation in 2nd set)
Which organs have a lower susceptibility to ischaemia?
those with a dual supply
- liver (portal venous and hepatic arteries)
- lungs (pulmonary venous and bronchial arteries)
- some parts of the brain (circle of willis)
What is repurfusion injury?
damage from ischaemia occurs mostly when perfusion is reestablished
How does reperfusion cause injury after ischaemia?
- blood returns + encounters tissue where transport mechanisms are damaged (especially impariment of Ca out of the cell)
- triggers activation of oxygen dependant free radical systems that clear away dead cells = damage
- macrophages + neutrophils clear away debris + import their own oxygen free radicals = damage
What is gangrene?
whole areas of limbs or guts have their arterial supply cut off + large areas of tissue die in bulk
What are the 2 types of gangrene?
- dry gangrene: tissues dies, mummifies and healing occurs over it = dead tissue drops off
- wet gangrene: bacterial infection occurs as a complication, spreads proximally = overwhelming sepsis = death
Where do MIs most commonly occur?
regional transmural MI (between endocardium and epicardium)
subendocardial MI: inner layer of heart more susceptible as blood comes in from outside = reduces BP
What are the other key causes of ischaemia and infarction?
- spasm of smooth muscle
- external compression
- steal (blood diverted from vital territories when other artery is atherosclerotic)
- hyperviscosity
- vasculitis (inflammation of vessel wall)
What is apoptosis?
cellular process where a defined and programmed sequence of intracellular events lead to the removal of a cell without release of harmful substances
What steps are involved in apoptosis?
enzymatic digestion of nuclear and cytoplasmic contents by macrophages
= enzymes cause organelles to shrink and die
breakdown products phagocytosed within cell membrane
What is the main difference between necrosis and apoptosis?
necrosis is unintended
apoptosis suppressed the inflammatory response caused by necrosis
Where is apoptosis normal?
in the gut
How can apoptosis cause cancer?
defective apoptosis leads to neoplasia = cancer as cells live longer
Give 3 examples of diseases caused by apoptosis?
AIDS, neurodegenerative disorders, anaemia
How does apoptosis lead to AIDS?
HIV proteins activate CD4 on uninfected T-helper lymphocytes
lymphocytes are apoptosed
= immunodepletion
What is apoptosis inhibited by?
growth factors
extracellular cell matrix
sex steroids
some viral proteins
What is apoptosis induced by?
growth factor withdrawal loss of matrix glucocorticoids some viruses free radicals ionising radiation DNA damage ligands binding to death receptors
How does the intrinsic pathway of apoptosis work?
Bcl-2: inhibits factors that induce apoptosis
Bax: enhances apoptopic stimuli
ratio of these determines a cell’s susceptibility to apoptosis
inhibit/activate caspases (enzymes which chew stuff up) which inhibits/activates apoptosis
What part does the p53 gene play in the intrinsic pathway of apoptosis?
induces cell cycle arrest + starts DNA damage repair
if damage is too difficult to repair, p53 induces apoptosis by activating Bax
How does the extrinsic pathway of apoptosis work?
activated by ligand binding at death receptors eg Fas ligand binds to a Fas receptor
activates caspases via a signal transduction cascade
= apoptosis
What is necrosis?
traumatic cell death which induces inflammation and repair
Why does necrosis happen?
due to failure to produce ATP
loss of plasma membrane integrity
What conditions can necrosis lead to?
frostbite, cerebral infarction, pancreatitis
What is coagulative necrosis?
commonest form, occurs in most organs
caused by ischaemia
tissues is firm then becomes soft as macrophages are digested
necrotic tissue causes an inflammatory response
What is liquifactive necrosis?
occurs in brain due to lack of supporting stroma
neural tissue liquifies
What is caseous necrosis?
dead tissue is structureless, like soft cheese
What is gangrene?
type of necrosis with rotting of tissue
tissue goes black
Why does tissue go black in gangrene?
deposition of iron sulphide from degraded Hb
Why is a possible cause of gangrene?
some certain bacteria
eg clostridia
What can caseous necrosis be a diagnosis for?
TB
What is the difference between the induction of apoptosis and necrosis?
apoptosis: physiological or pathological stimuli
necrosis: usually pathological injury
What is the difference between the extent of apoptosis and necrosis?
apoptosis: single cells
necrosis: cell groups
What is the difference between the biochemical events of apoptosis and necrosis?
apoptosis: energy-dependent fragmentation of DNA by endonucleases, lysosomes intact
necrosis: energy failure, impairment of homeostasis, lysosomes leak lytic enzymes
What is the difference between the cell membrane integrity of apoptosis and necrosis?
apoptosis: maintained
necrosis: lost
What is the difference between the morphology of apoptosis and necrosis?
apoptosis: cell shrinkage and fragmentation = apoptopic bodies with dense chromatin
necrosis: cell swelling and lysis
What is the difference between the inflammatory response of apoptosis and necrosis?
apoptosis: none
necrosis: usual
What is the difference between the fate of dead cells of apoptosis and necrosis?
apoptosis: ingested by neighbouring cells
necrosis: ingested by neutrophil polymorphs and macrophages