wk 1 7 Physiology of Digestion and Absorption 1 Flashcards
the small intestine recieves chyme from stomach, pancreatic juice and bile from gall bladder. Through which sphincter are each received from
Chyme - pyloric sphincter
Pancreatic - sphincter of Oddi
Bile - sphincter of Oddi
name given for intestinal juice secreted by small instestines
succus entericus
name of valve which moves the remaining residues from small to large intestine
ileocaecal valve
3 components of small intestine
duodenum
jejunum
ileum
what aspects of small intesting increase the surface dimension, which one is the greatest
circular folds of kerckring
villi
microvilli (largest)
what are the secretions of the small intestine (7)
gastrin ghrelin glucagon-like insulinotropic peptide (GIP) glucagon-like peptide-1 (GLP-1) cholecystokinin (CKK) secretin motiilin
cells which both the duodenum and jejunum secrete
CCK - from I cells
Motilin - from M cells
GIP - an incretin from K cells
effect of incretins on pancreas
act upon beta cells, stimulate release of insulin
3 areas where ghrelin is secreted from
Gr cells from gastric antrum (outlet proportion, no acid)
small intestine
pancreas
also elsewhere
L cells of the gut secrete
GLP-1
t/f gastrin cholecystokinin (CKK) secretin motiilin glucagon-like insulinotropic peptide (GIP) glucagon-like peptide-1 (GLP-1) ghrelin these secretions act on G-protein coupled receptors
true
the mechanisms involved of secretion are:
distension/irritation, gastrin, CKK, secretin, para/sympa nerve activity
which ones increase/decrease secretion
all except sympa enhance
t/f secretion of small intestine contains no digestive enzymes
true
aqueous salt is part of the secretion of small intestines, what is its purpose
enzymatic digestion
function of ‘chopping’
moves chyme back and forth in stomach
t/f segmentation (mixing) involves the alternating contraction/relaxation of longlitudinal muscles
false
it is the contraction/ relaxation of circular muscle
what is BER of GI
what initiates BER
where are these cells located in stomach, small/large intestine
Basal Electrical rhythm, controls contraction Pacemaker (interstitial cells of Cajal) Stomach- longitudinal Small- circular Large- circular
in the duodenum, what activates segmentaion
distension by entering chyme
define distension
outward expansion of stomach
segmentation in the empty ileum is triggered by gastrin from the stomach, name given for this reflex
gastroileal reflex
Migrating Motor Complex (MMC) is on the activities occurring in he fasting state, explain what it does
clears small intestine through peristalsis
what inhibits MMC
feeding and vagal activity (remeber:activity of fasting statw)
what triggers/suppresses MMC)
motilin triggers
gastrin and CCK suppress
pancreatic juice is an exocrine secretion, what does it consist of
digestive enzymes (acinar cells) aqueous NaHCO3- solution (duct cells)
insulin and glucagon are endocrine pancreatic secretions, how are they secreted
via blood
t/f acidic solutions are high in HCO3-
false
alkaline solutions are high in HCO3- (duct cells)
effect of pancreatic duct cells
neutralises acidic chyme entering duodenum, providing optimum pH and protects mucosa
t/f amylase and lipase enzymes do not require activation once secreted to the duodenum
true
amylase and lipase are both pancreatic*
4 proteases require activation by enterokinase (mucosal cells) when entering the duodenum, what are their inactivated names
trypsinogen
chymotrypsinogen
procarboxypeptidase A and B
when would enzymes stored in the zymogen granules of acinar cells be released
in response to elevated Ca2+
what does the activation of trypsin autocatalyse
chymotrypsinogen - chymotrypsin
procarboxypeptidase AandB - carboxypeptidase AandB
`what does amylase catalyse
hydrolysis of starch into sugars
what does lipase do
breaks down fats into monoglycerides and 2 fatty acids
outline the pancreatic control of acid levels
acid in duodenal lumen
increase in secretin release from S cells
activates pancreatic duct cells, increases secretion of aqueous NaHCO3 solution
outline pancreatic secretions control on digestion
fat and protein in duodenum
incr CCK release from I cells
activates acinar
incr secretion of digestive enzymes in duodenum (lipase,amylase, procarboxypeptidase AandB, chymotrypsinogen, trypsinogen)
what mediates the membrane digestion in the small intestines
enzymes situated at the brus border of epithelial cells
define absorption
absorbable products of digestion are transferred across the apical (brush border) and basolateral membranes of enterocytes
what are enterocytes
absorptive cells of intestinal epithelium
name given for overall process of digestion and absorption
assimilation
