Nutrient absorption and transit Flashcards
what prevents chyme moving from stomach to the duodenum
pylorus sphincter
what hormones prevent the pylorus sphincter opening
secretin
cholecystokinin
exocrine pancreas function
provides main digestive fluid of small intestine
empties into duodenum via pancreatic duct/common bile duct
what does the pancreatic secretion consist of
water
bicarbonate
enzymes
what is the function of the bicarbonate in the pancreatic secretion
neutralises acid in chyme
what are the enzymes in the pancreatic secretion
trypsin(OGEN) chymotrypsin(OGEN) amylase lipase nuclease STORED INACTIVE - ZYMOGENS
when are the enzymes from the pancreatic secretion activated
when reach duodenum
what is the function of trypsin(ogen) enzyme in pancreatic secretion
‘chop’ different points of polypeptide chains
what is the function of lipase in the pancreatic secretion
break down fat
what is the function of amylase in the pancreatic secretion
polysaccharide digestion
what is the function of nuclease in the pancreatic secreiton
break all nucleic acids
what is the function of chymotrypsin(ogen) in the pancreatic secretion
‘chop’ different point on polypeptide chains
what is involved in the neurological control of the pancreas
parasympathetic nerves
- acetylcholine
- vasoactive intestinal peptide
what is involved in the hormonal control of the pancreas
secretin (made in response to acid, it causes response to release bicarbonate)
cholecystokinin (made in response to fats/amino acids)
what does synergistic mean in relation to the neurological and hormonal stimulatory factors
they work better when both in action
how is trypsin activated
trypsinogen (inactive precursor) contact with mucosa lining in duodenum
enterokinase (intestinal brush border) enzyme cuts off inactive part of trypsinogen
trypsin catalyses conversion of all other enzyme precursors to active
what is the third site of infection protection
immune cells in liver
how many litres of bile are made per day and where is it produced
0.7-1.2 litres a day
in the liver
where is bile stored
gall bladder
how is bile used in digestion
emulsifying agent - fat absorption aider
what is bile mainly made up of
mainly made of cholic acid and chenodeoxycholic acid
can contain cholesterol and lecithin
an example of bile - excretory
breakdown products of metabolism
e.g. haemoglobin, break down products are bile pigments
biliverdin (green)
bilirubin (red)
they’re converted to stercobilin (brown) (also use bacteria)
what is the release of bile dependent on
cholecystokinin - causes the bladder contraction and relaxation of sphincter of oddi
how can a fat molecule pass through the ‘unstirred’ layer - aqueous and acidic
what must happen when inside
when bile salts form around - hydrophilic tail attaches to fat - hydrophobic head form micelles, diffuse through need to have contact with the villus tip so nutrients absorbed
