infarction and necrosis

Question 1

what is apoptosis?

Answer 1

• programmed cell death
• 50–70 billion cells undergoing apoptosis per day in an adult human
• highly-regulated process of self degradation

Question 2

what does apoptosis eliminate?

Answer 2

• unwanted cells
• dysfunctional cells

Question 3

changes to structure of cells - apoptosis

Answer 3

• genome fractures
• cell shrinks
• disintegrates in small apoptotic bodies

Question 4

what are caspases?

Answer 4

• proteins that break down old or faulty cells
• can be activated via intrinsic/extrinsic pathway

Question 5

apoptosis is initiated by…

Answer 5

factors outside the cell in the extrinsic pathway

Question 6

when triggered internally…

Answer 6

proteins within cells are released which destroy membranes of mitochondria - this is how intrinsic pathway begins

Question 7

inducers of apoptosis?

Answer 7

• TNF
• reduction of growth factor
• toxins
• UV + gamma radiation
• nutrient deprivation

Question 8

what does excessive apoptosis lead to?

Answer 8

neurodegenerative disease

Question 9

what does insufficient apoptosis lead to?

Answer 9

cancers, autoimmunity

Question 10

what is necrosis?

Answer 10

• death of a cell caused by external factors such as injury, chemical exposure, radiation, or lack of oxygen
• it’s permanent

Question 11

apoptosis vs necrosis

Answer 11

Question 12

ischaemia

Answer 12

• inadequate supply of blood to an area of tissue
• cause hypooxia, malnutrition, failure to remove waste
• caused by interruption of arterial supply

Question 13

consequences of ishaemia

Answer 13

• functional disturbances
• degeneration atrophy + replacement fibrosis
• gangrene
• infarction

Question 14

infarction

Answer 14

area of necrosis caused by arterial/venous ischaemia

Question 15

infarction causes

Answer 15

• thrombus
• emoblism
• hypovolaemia
• hypotension

Question 16

factors which determine the degree of infarction or necrosis

Answer 16

• speed of onset - if sudden, then there is less time to use collateral circulation
• extent of obstruction, complete, partial occlusion
• anatomy - eg dual supply, shins (watershed)
• vulnerability to hypoxia - neurones, myocardium, fibroblasts
• oxygenation - before event
• duration

Question 16

example of small area of necrosis - acute leucocytoclastic vasculitis

Answer 16

affected vessels w necrosis have their lumens occluded by fibrin and walls infiltered by neutrophils showing degeneration with karyorrhexis + clinically skin appears as palpable purpura

Question 17

infarction development

Answer 17

1. death of cells in an area deprived of blood supply
2. dead tissue undergoes necrosis
3. progressive autolysis of necrotic tisssue + haemolysis of red cells
4. outward diffusion of tissue breakdown products + free haemoglobin ingested by macrophages
5. infarct is now firm + dull, yellow in colour surrounded by red zone of inflammation
6. followed by shrinkage of infarct which later becomes white in colour

Question 18

types of infarctions

Answer 18

• red (haemorrhagic) infarcts - venous occlusion
• white infarcts - arterial occlusion