enteric infections Flashcards
repeat enteric infections can lead to
malnutrition
growth stunting
cognitive impairment
impaired immunity (with vaccine hyporesponsiveness)
definition of diarrhoea
increased stool water causing
- an increase in stool frequency
- the passage of soft stools
- the passage of greater than 3 stools per day or stool volume of greater than 200mls
acute diarrhoea
lasting less than 2 weeks
chronic diarrhoea
lasting more than two weeks
small intestine
6m ling in adult human short duodenum jejunum 40% of length ileum 60% of length absorbs - all amino acids - all sugars - most lipids - 80% of water
surface area of the small intestine is increased by
mucosal folds
villi and crypts
microvilli and enterocytes
large intestinal structure
lacks folds or villi
has crypts
site of water absorption
dependant on Na absortoin
water flux in the intestine
inputs 9L
reabsorbs 8.8L
excretes 0.2L in stool
even a small disturbance in flux can result in diarrhoea
water in the intestine follows
osmotic gradients osmotically active molecules include - electrolytes - sugars - amino acids
secretion in the small intestine
to distinct processes establish as osmotic gradient which pulls water into the small intestine lumen
- digestion of food into small molecules of high osmolarity
- active secretion of electrolytes by crypt enterocytes
active secretion of electrolytes by crypt enterocytes
cyclic AMP activates the transmembrane chloride channel.
chloride is pumped into the lumen
how is water reabsorbed from the lumen
sodium dependant hexose transporter
coupled transport of Na+ and glucose into the enterocyte
high sodium concentration is largely responsible for absorption of water in the small intestine
oral rehydration solutions
goal is to increase presence of sodium and glucose in enterocyte cell
mechanisms of diarrhoea production
- increased active secretion of electrolytes and thus water
- damage to brush border resulting in malabsorption of nutrients and electrolytes
- damage to brush border, loss of disaccharide activity, increase osmolarity of stool
- altered motility, less time for water absorption
4 classifications of diarrhoea
- inflammatory
- secretory
- osmotic
- motility related
type of diarrhoea is dependant upon the virulence factors expressed by the pathogen
main virulence factors
- those enabling adhesion
- those enabling invasion
- those having toxins
types of toxin production
- enterotoxins - work on the enterocyte (don’t damage it)
- cytotoxins - damage the enterocyte
- neurotoxins - stimulate the smooth muscle of the bowel
enterotoxins
interfere with the salt and water transport without damaging the enterocyte itself
result sin net loss of water
can use rehydration solutions in these cases