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What is involved in the maintenance of cellular steady state?

- preservation of genetic integrity
- normal enzyme content
- intact membranes and transmembrane proteins
- adequate supply of substrates and oxygen


What happens when cellular steady state is not maintained?

Cell injury.

Biochemical and/or morphological changes that occur when the steady state is perturbed by adverse influences


What happens when normal cell homeostasis is disrupted?

The cell either adapts or becomes injured. Cell injury can be mild and transient and therefore reversible, or it can be severe and progressive and therefore irreversible


What does irreversible cell injury lead to?

Cell death

Either necrosis or apoptosis


Name three types of cellular adaptation

- increased cellular activity (hyperplasia, hypertrophy)

- decreased cellular activity (atrophy)

- change in cell morphology (metaplasia)


Define hypertrophy

Individual cells increase in size (since the cells cannot divide)

Eg. Size and thickness of left ventricle increase due to systemic hypertension etc, muscle gets bigger


Define hyperplasia

The cell number increases, cells divide


Define atrophy

Cells shrink in size or number due to decreased demand


What effect do steroids have on the body in terms of cellular adaptations?

When used for a long time, steroids cause the adrenal glands to become atrophic - this then creates a problem if the steroids are stopped suddenly, it is recoverable if you reduce steroids slowly


Explain metaplasia

When cells change their shape and morphology in response to a change in stimulus - change function

Can be physiological or pathological

Physiological example = cervix goes through change from columnar to squamous epithelium


Give a physiological and pathological example of atrophy

Physiological = organ formation in embryology

Pathological = loss of innervation leading to muscle atrophy


Give a physiological and pathological example of hypertrophy

Physiological = skeletal and heart muscle in athletes

Pathological = left ventricular hypertrophy in response to systemic hypertension


Give a physiological and pathological example of hyperplasia

Physiological = increase in bone marrow cells producing red blood cells at high altitude

Pathological = angiogenesis in wound repair


Give an example of metaplasia

Barrett's oesophagus = replacement of normal squamous epithelium with columnar glandular epithelium due to gastric acid reflux


Define hypoxia and anoxia

Hypoxia = reduction of oxygen to delivered to cells, often cause by ischaemia

Anoxia = complete loss of oxygen to cells


Define ischaemia

Lack of blood flow. Therefore a common cause of tissue hypoxia


Other than ischaemia, how else might tissue hypoxia arise?

There might not be enough oxygen in the blood to start off with, or the cells might not be able to use the oxygen (eg. Cyanide poisoning)


Explain reoxygenation

Reperfusion - generation of oxygen free radicals.

If an artery becomes infarct, and then the infarct artery becomes patent again (eg. In thrombolysis) some of the myocardium will be reperfused, this creates free radicals which can cause cell death.

So reperfusion is helpful but can also cause problems


How might a bullet shot affect tissues?

Tear small blood vessels over a large area leading to widespread devascularisation and subsequent ischaemic tissue death

The cavity also contains a vacuum and so dirt is sucked into the wound leading to infection


How does mechanical trauma cause cell injury?

Disrupts cell structure

Damages to walls of blood vessels leading to thrombosis and secondary ischaemic damage


Define hyperprexia

A fever with extreme elevation of body temperature greater than or equal to 41.5 degrees celcius

(Extreme temperature damage can be both internal or external)


Give examples of chemical agents that can cause cell injury

- alcohol
- tobacco smoke
- drugs
- poisons
- environmental
- occupational


What is the mode of action of chemical agents in terms of cell injury?

Different modes of action

Range from simple denaturation and breakdown of macromolecules (eg. Strong acids and alkalis)

To more subtle interferences will cellular metabolism (eg. Paracetamol poisoning)


Describe liver cirrhosis in terms of cell injury

Alcohol abuse causing long term cell injury and death, the liver tries to regenerate in a suboptimal way


What are the carcinogenic effects of asbestos?

Causes cancer of the bronchi and pleura.

Often happens 20 to 30 years after the exposure

Can also affect those living with the exposed person (on their clothes etc)


What are the two types of bacterial toxin?

Exotoxin = secreted from living bacterial cell eg. Pseudomembranous colitis

Endotoxin = secreted from the dead bacterium eg. E. coli


How do X-rays cause cell injury?

Generation of free radicals and direct damage to macromolecules

Free radicals are very reactive and cause bonds to form where they shouldn't, causing damage


Which organs are most sensitive to ionising radiation?

Those with a high turnover rate (high proliferation rate)

Eg. Bone marrow, gonads, intestines


Which organs are not as sensitive to ionising radiation?



Adrenal glands


How does UV light cause cell injury?

Can induce an inflammatory response several hours after exposure

Eg. Sunburn