Injuries to cells

Question 1

Define hypertrophy

Answer 1

increase in the size of cells, resulting in increase in size of organ

Question 2

Define hyperplasia

Answer 2

increase in cell number resulting in a larger organ

Question 3

Define atrophy

Answer 3

shrinkage of the size of the cell by loss of cell substance

Question 4

Define metaplasia

Answer 4

one adult cell type is replaced by another adult cell type e.g barrett’s oesophagus

Question 5

Name the 3 main causes of cell injury

Answer 5

hypoxia - low O2 supply
ischaemia - loss of blood supply
chemical exposure

Question 6

Name the other causes of cell injury

Answer 6

infection, radiation, lack of nutrients, immunologic reactions, ageing.

Question 7

What is necrosis?

Answer 7

Type of cell death. Damage to membranes allows enzymes to digest the cell.

Question 8

What is apoptosis?

Answer 8

Programmed cell death. Irreparable damage to cell’s protein/DNA or deprived of growth factors.

Question 9

How does apoptosis work?

Answer 9

Programmed cell death pathway. Cells activate enzymes that degrade the cells own DNA and proteins, resulting in death. Membrane remains intact so no contents leak out and no response is triggered. Bits of the cell break off. Dead cell rapidly removed by phagocytosis.

Question 10

What is physiological apoptosis?

Answer 10

Elimination of cells which have served their purpose e.g menstruation

Question 11

What about apoptosis in pathological conditions?

Answer 11

A sign of disease or damage.

Question 12

Name the 4 types of necrosis.

Answer 12

Coagulative
Liquefactive
Caseous
Fat

Question 13

What are the different mechanisms of cell injury?

Answer 13

depletion of ATP
mitochondrial damage 
influx of calcium 
oxidative stress
damage to the cell membrane 
DNA damage

Question 14

What is the depletion of ATP?

Answer 14

ATP is the energy store of cells. Oxidative phosphorylation of ADP within mitochondria. Reduced supply of oxygen and nutrients, mitochondrial damage, poisons.

Question 15

What is mitochondrial damage?

Answer 15

Mitochondria are sensitive to many types of stress e.g hypoxia, chemical poisons, radiation. Effects = failure of production of energy

Question 16

What is influx of calcium?

Answer 16

Caused by ischaemia and certain poisons. Effects = activation of enzymes and damage to cellular components.

Question 17

What is oxidative stress?

Answer 17

Accumulation of reactive oxygen species. React with and damage proteins, fat, DNA, and create more of themselves in the process.

Question 18

What are the defects in membrane permeability?

Answer 18

They result in necrosis. Various sites of damage: mitochondrial membrane, plasma membrane, lysosomal membrane.

Question 19

What is neoplasia?

Answer 19

gene mutation caused by mild DNA damage. Mutations accumulate and eventually lead to abnormal cells and then cancer.