Cell Injury And Death

Question 1

What do the degrees of injury depend on?

Answer 1

Type of injury, severity of injury, duration of injury, type of tissue.

Question 2

What are causes of cell injury?

Answer 2

Environmental- hypoxia, toxins, infection. Non-environmental- genetic, ageing.

Question 3

What is hypoxia and what are causes?

Answer 3

Hypoxia is oxygen deprivation. There are different causes: hypoxaemic hypoxia- arterial content of oxygen is low, anaemic hypoxia- decreased ability of haemoglobin to carry O2, ischaemic hypoxia- interruption to blood supply, histiotoxic hypoxia- inability to utilise oxygen due to disabled oxidative phosphorylation enzymes.

Question 4

What are common mechanisms of cell injury?

Answer 4

Depletion of ATP, direct mitochondrial damage, disruption to calcium homeostasis, oxidative stress and direct damage to DNA+ proteins.

Question 5

Describe ATP depletion.

Answer 5

Cells deprived of oxygen -> reduction in oxidative phosphorylation -> mitochondrial ATP production stops.

Question 6

What do free radicals damage?

Answer 6

Lipids, proteins and DNA.

Question 7

Describe free radical lipid damage.

Answer 7

Unsaturated fatty acids get attacked by free radicals, this causes cell membrane and organelle damage. This results in calcium influx, damage to Na/K pump.

Question 8

Describe free radical lipid damage.

Answer 8

Unsaturated fatty acids get attacked by free radicals, this causes cell membrane and organelle damage. This results in calcium inf

Question 9

Describe free radical DNA damage.

Answer 9

Free radicals target nuclear and mitochondrial DNA, they cause single and double strand breaks in DNA

Question 10

How does the body control free radicals?

Answer 10

Anti-oxidants: lipid soluble vitamins, ascorbic acid, glutathione. Transport proteins: iron binds to transferrin, copper binds to ceruloplasmin. Enzymes: Superoxidase dismutases, glutathione peroxidase.

Question 11

What do heat shock proteins do?

Answer 11

They help repair and re-fold damaged proteins, or they label them for degradation.

Question 12

What are reversible and irreversible changes in an injured cell?

Answer 12

Reversible: Swelling (due to Na/K+ pump failure), clumped chromatin (due to reduced pH), ribosome dispersion (lack of ATP), cytoplasmic blebs. Irreversible: nuclear changes, lysosome rupture, membrane defects and lysis of endoplasmic reticulum.

Question 13

What is apoptosis?

Answer 13

Individual programmed cell death. It can be pathological or physiological. Physiological- embryogenesis, involution of hormone dependent tissue. Pathological- cell death in viral infection, cells with damaged DNA.

Question 14

What are the two pathways of apoptosis?

Answer 14

Intrinsic- mitochondria release cytochrome C which activate capases which induce apoptosis. Extrinsic- death receptors attach to the cell membrane which then activate capases which lead to cell death

Question 15

What is necrosis?

Answer 15

In a living organism, the morphological changes that occur after a cell has been dead some time.

Question 16

What are the types of necrosis?

Answer 16

Coagulative, liquefactive, caseous, fat necrosis, fibrinoid necrosis.

Question 17

What is coagulative necrosis?

Answer 17

Occurs in solid organs, it retains a ghost outline of cells and tissue architecture. Protein desaturation is prominent in the cell injury/death.

Question 18

What is liquefactive necrosis?

Answer 18

Loose tissue dies, a complete loss of architecture, release of enzymes which break down tissue.

Question 19

What is caseous necrosis?

Answer 19

Seen in the lung in TB, ‘cheese’ like

Question 20

What is fat necrosis?

Answer 20

Direct trauma to fatty areas, acute pancreatitis

Question 21

Apoptosis vs Necrosis

Answer 21

Apoptosis- Single cell death, cell shrinks, plasma membrane is preserved, organelles contract, dead cells taken up by phagocytes.
Necrosis- grouped cell death, cell swells, plasma membrane destroyed, organelles swell and break down, dead cells start inflammatory process.

Question 22

What molecules are released by injured cells?

Answer 22

Potassium, enzymes and myoglobin

Question 23

Describe intra-cellular accumulations.

Answer 23

Accumulations can be: normal cell components, abnormal components, pigment.

Question 24

Example of normal cell component.

Answer 24

Cerebral oedema: hypoxic cell injury, sodium enters cell and water follows causing cell swelling.

Question 25

Examples of pigment.

Answer 25

Tattoo: artificial pigment into skin, pigment phagocytosed by macrophages and pigment remains in macrophages of dermis.

Question 26

Example of abnormal cell component.

Answer 26

Fatty liver disease: liver cell injury, deranged metabolism, fat accumulation within hepatocytes.

Question 27

What can happen when the cell dies?

Answer 27

Gangrene= necrosis visible to the naked eye. Infarction= necrosis caused by reduction in arterial blood flow (cause of necrosis can result in gangrene). Ischaemia= inadequate blood supply to tissue (can result in infarction).

Question 28

What is pathological calcification?

Answer 28

Abnormal deposition of calcium within tissues.