What causes diarrhoea?
- Damage to epithelial cells lining the intestine.
- Loss of microvilli due to toxins.
- Excessive secretion of water due to toxins e.g. cholera toxin.
Excessive fluid is lost and/or insufficient fluid taken in = dehydration, may be fatal.
What is oral rehydration therapy?
Drinking water is ineffective for rehydrating diarrhoea patient because:
- Water not being absorbed in small intestine - sometimes e.g. cholera it is lost from the cells too.
- Drinking water doesn't replace lost electrolytes (ions) being lost from epithelial cells.
More than one type of carrier protein in cell-surface membranes of epithelial cells that absorbs sodium ions.
As sodium ions are absorbed, water potential of cells falls and water enters by osmosis.
Rehydration solution therefore needs:
- Water = rehydrates tissues.
- Sodium = replaces lost sodium ions, makes optimum use of sodium-glucose carrier proteins.
- Glucose = stimulates uptake of sodium ions, provides energy.
- Potassium =…