Cell injury and fate

Question 1

what happens when there is a lethal cell injury?

Answer 1

cell death

Question 2

what happens when there is a sublethal cell injury?

Answer 2

may be reversible or progress to cell death

Question 3

list the different causes of cell injury

Answer 3

1) oxygen deprivation (critical)
2) chemical agents e.g. drugs
3) infectious agents
4) immunological reactions e.g autoimmune
5) genetic defects e.g. chromosomal
6) nutritional imbalances
7) physical agents e.g. bullet wound, radiation
8) ageing

tissue injury can be driven by some of processes

Question 4

how does a myocardial infarction occur?

Answer 4

blocked blood flow → extreme ischemia → cell death of tissue → infarction

Question 5

what do the cellular responses depend on?

Answer 5

1) type of injury
2) duration
3) severity

also depends on tissue type (type of cell + status) e.g. gut lining and bone marrow have a higher turn over rate

Question 6

what intracellular systems are particularly vulnerable to injury?

Answer 6

1) cell membrane integrity -immediate
2) ATP generation - quick
3) protein synthesis - takes a while but has knock on effect on enzymes
4) the integrity of the genetic apparatus (DNA)

Question 7

when is cellular function lost during cellular injury?

Answer 7

lost before cell death occurs which happens before morphological changes

Question 8

define “atrophy”

Answer 8

shrinkage in size by loss of cell substance

e.g. dementia = brain atrophy, or at a cellular level, muscle atrophy e.g. if nerve to muscle has been cut

Question 9

define “hypertrophy”

Answer 9

incr. in size of cell therefore increase in size of an organ

e. g. uterus in pregnancy is an extreme example of hypertrophy – as it is not proliferation the cells just gets bigger

Question 10

define “hyperplasia”

Answer 10

incr. in no. of cells in organ
- physiological hyperplasia can be either hormonal or compensatory.
- pathological hyperplasia is usually due to excessive hormonal or growth factor stimulation.
e. g. proliferating endometrium such as during menstruation, kidney removal – other kidney gets bigger to compensate with the lack of the other kidney

Question 11

define “metaplasia”

Answer 11

A reversible change in which one adult cell type is replaced by another

e. g. columnar epithelium in the cervix becomes squamous during pregnancy due to vaginal pH change.
e. g. barrettes oesophagus

Question 12

define “dysplasia”

Answer 12

Precancerous cells which show the genetic and cytological features or malignancy but not invading the underlying tissue

-pre-cancerous cells that have an increase in nuclear cytoplasmic ratio → nucleus gets bigger without the cell getting bigger

Question 13

what are different morphological changes associated with reversible injury?

Answer 13

• fatty change e.g. alcohol fat

- cellular swelling

Question 14

define the term “necrosis”

Answer 14

confluent cell death (whole areas of cells dying) with inflammation

Question 15

what are the different types of morphological changes associated with irreversible injury?

Answer 15

1) coagulative necrosis
2) liquefactive necrosis
3) caseous necrosis
4) fat necrosis

Question 16

what happens during coagulative necrosis?

Answer 16

cells keep their shape but there are changes e.g. cells lose their nuclei, cells that are inflammed

Question 17

what happens during liquefactive necrosis?

Answer 17

liquefied filled spaces especially as brain lacks supporting framework

Question 18

what happens during caseous necrosis?

Answer 18

“cheesy” texture → no architecture/structure, just granular and there is inflammation

Question 19

what happens during fat necrosis?

Answer 19

1) lipase activated in the wrong place
2) will start to digest the fat around the pancreas (fatty acids + glycerol) so there is free fatty acids
3) bind to calcium ]
4) cause white spots around the pancreas

Question 20

define “apoptosis”

Answer 20

programmed cell death

Question 21

what are the different causes of apoptosis?

Answer 21

1) embryogenesis → development of an embryo e.g. with fingers
2) deletion of auto reactive
3) hormone dependent e.g. menstrual cycle
4) cell death in proliferating populations e.g. skin and gut proliferating all the time and apoptosis is a safe way for cells to die
5) mild injurious stimuli causing irreparable DNA damage → apoptosis

Question 22

what are the key differences between apoptosis and necrosis?

Answer 22

1) apoptosis may be physiological
2) apoptosis = active therefore requires ATP
3) apoptosis no inflammation
4) apoptosis single cell
5) apoptosis not very severe

• apoptosis→ death of a single cell with no inflammation around it
• necrosis → many cell deaths with inflammation

Question 23

define “necroptosis”

Answer 23

programmed cell death associated with inflammation

-it is energy dependent like apoptosis but there is inflammation like necrosis

Question 24

what can cause necroptosis?

Answer 24

eg. viral infections

Question 25

why does necrosis cause inflammation but not apoptosis?

Answer 25

apoptosis cell membrane is intact so no cytoplasm released and then phagocytosis gets rid of the broken down cell