Cell Death

Question 1

Name the 2 types of cell injury

Answer 1

Reversible cell injury
Irreversible cell injury

Question 2

Reversible injury

Answer 2

Functional and morphological changes are reversible if a damaging agent is removed
Cell has reduced oxidative phosphorylation leading to ATP depletion
Changes in Na+ concentration leading to influx of H2O
Cellular swelling

Question 3

Irreversible cell injury

Answer 3

Mitochondrial injury irreversible
Na+ in cell leading to irreversible membrane defects
Lysosomal digestion

Question 4

Causes of cell injury

Answer 4

Hypoxia
Mechanical trauma
Glucose, salt and O2
Microbes
Autoimmune disease
Nutritional imbalances
Genetic dearrangements

Question 5

What are the 3 types of cell death

Answer 5

Necrosis
Apoptosis
Autophagy

Question 6

Apoptosis

Answer 6

Programmed cell death
Happens during embryonic development as new tissues are formed and remodeled
Happens in physiological events
Needs energy
Orderly breakdown of cellular constituents which are packed into membrane bound vesicles called apoptotic bodies and tagged for phagocytosis
It’s irreversible involving final pathway of an intracellular cascade of caspases
Has no inflammatory response

Question 7

Events in apoptosis

Answer 7

Binding of death ligand TNFR1 or Fas on cell membrane
Membrane disruption by perforin, intracellular injection of granzyme B by cytotoxic T cells
Release of pro-apoptotic proteins cytochrome from leaky mitochondrial membrane. Regulated by pro- and anti-apoptotic proteins of Bcl family
Gate keeper gene in cell cycle P53 protein instigates apoptosis if there is failure to repair DNA damage
Proteolytic cleavage of cell contents and H2O loss cause shrinkage
Fragments bud off enveloped by apoptotic bodies with new ligands for phagocytosis
Macrophages and adjacent cells bind new ligands and phagocytose the fragments

Question 8

Necrosis

Answer 8

Cell suicide
Death of cells due to noxious stimulus
Caused by physical and chemical agents
Has inflammatory response(acute)
Reversible
Irreversible when there is loss of membrane integrity and influx of Ca2+ into cytosol from interstitial fluid or ER

Question 9

Factors that influence damage as reversible or irreversible in necrosis

Answer 9

Duration of stimuli - longer, irreversible but shorter, reversible
Dose of chemical agents - different for each individual genetic polymorphism
Tissue type and metabolic activity
State of health of existing tissue

Question 10

Types of necrosis

Answer 10

Coagulative necrosis
Liquifactive necrosis
Lytic necrosis
Caseation
Gangrene
Fat necrosis
Infarction

Question 11

Coagulative necrosis

Answer 11

Common
Appears as firm, pale, wedge shaped region of tissue reflecting territory supplied by occluded atriole
Affected cells retain shape but loss nuclei

Question 12

Liquifactive necrosis

Answer 12

Affects CNS after stroke
No healing after removal of damaged tissue
Cystic space

Question 13

Lytic necrosis

Answer 13

Mediated by cytokines
Loss of a single cell without any remaining evidence once the process is complete
Appears in liver

Question 14

Caseation

Answer 14

White, crumbly, cottage cheese like appearance found in tuberculosis
Mixture of coagulative and liquifactive necrosis

Question 15

Gangrene

Answer 15

Dry gangrene is black, dead, dry tissue caused by infarction
Gas gangrene happens when dead, anoxic tissue is infected by gas forming organisms
Wet gangrene happens when the infarcted region becomes infected

Question 16

Fat necrosis

Answer 16

Hard, bright yellow, nodules of fat necrosis
Happen secondary to trauma
May calcify
Resembles tumor

Question 17

Infarction

Answer 17

Tissue or organ necrosis due to interruption of its blood supply
Can be an arterial where there is not enough blood flow into the organ and is due to the occlusion of the vessel by thrombus or embolus
Can be venous where out flow is obstructed preventing flow through organ causing congestion and stagnation. Reflects compression of vein resulting in congestion exacerbates strangulation

Question 18

Autophagy

Answer 18

Seen in starvation and infection
Body attempts to preserve cells through starvation
Initiated by growth factor deprivation
Portions of cytoplasm are bound by membrane to form vesicle, autophagosome, fuses with lysosome and its contents degraded by hydrolase and recyclesd
Reversible when lean times are over
Cell death happens when stimuli persists

Question 19

Autophagy

Answer 19

Seen in starvation and infection
Body attempts to preserve cells through starvation
Initiated by growth factor deprivation
Portions of cytoplasm are bound by membrane to form vesicle, autophagosome, fuses with lysosome and its contents degraded by hydrolase and recyclesd
Reversible when lean times are over
Cell death happens when stimuli persists