Physiology of digestion and absorption - consolidation Flashcards
what is absorbed in the ileum
micronutrients (eg vitamin b12)
4 juices secreted in small intestine
chyme
pancreatic juice
bile
succus entericus
another name for the brush border
microvilli
7 hormones secreted by the small intesine
Gastrin Ghrelin GLP-1 GIP CKK secretin Motilin
other than the duodenum, where is gastrin released
from g cells of gastric antrum
GIP is an incretin, what is this
act upon Beta cells of pancreas, stimulate release of insulin
which other hormone is an incretin
GLP-1
functions of ghrelin
increass appetite
3 gut hormones associated with enhances peristalsis
gastrin
CKK
secretin
3 components of secretion
mucus - protection/lube
aqueous salt - for enzymatic digestion
no digestive enzymes
3 channels involved in the secretiojn
NA+/K+ ATPase
Na+/K+/2Cl- co-transporter
Chloride channel (CFTR)
where are the aqeuous salts secreted from (mostly)
crypts of Lieberkuhn
bottom areas of villi
sodium chloride and accompanying water are moved in what direction
basolateral membrane - lumen
what drives the co-transporter
low intracellular conc of Na
secondary active transport
how does chlorine enter lumen
difference in electrochemical gradient, incr in chloride in basolateral membrane when pumpeed in, CFTR balances
factors of cystic fibrosis in intestine
cystic fibrosis - not only sticky mucus, electrolytes and enzymes decr.
t/f K,Na,Cl, and H20 are found in lumen
false
K is not (or not as much)
when does segmentation occur
during meal
very rigorous after meal
(little/none between)
which hormone triggers segmentation, when does it occur, what is this reflex called
gastrin
when empty, anticipation of food
gastroileal reflex
MMC characteristic
clears small intestine of debris,mucus and soughed epithelial cells
goes through full smll intestin
which hormone triggers MMC
motilin
which 2 hormones suppress MMC
gastrin
CCK
t/f vagal activity enhances MMC
false
inhibited by feeding and vagal
macroslide antibiotics mimic effect of
motilin
triggers MMC
may cause GI disturbances
for pancreatic duct cells, chloride is secreted in via CFTR, yet recycled. what is it exchanged for when it enters the lumen
HCO3-
for neutralisatin
3 proteases secreted by pancreas
trypsinogen
chymotrpysinogen
procarboxypeptidase A and B
which duodenum enzyme activates pancreatic proteases
enterokinase
3 phases of control of pancreatic secretion (cephalic, gastric, intestinal)
cephalic - mediated by vagal (due to acinar)
gastric -distension evokes vagovagal reflex, parasympa stimulation of acinar and duct cells
intestinal - majority of secretion, due to release of secretin/CKK
t/f disaccharides can be absorbed
false
only monosaccharides
gluocse/galactose ect
t/f tetrapeptides can be absorbed
true
usually broken down in epithelium
differenc in links in amylose and amylopectin (starch compounds)
amylose - str8 chain
alpha 1,4 links
amylopectin - branches
alpha-1,4
alpha-1,6
when starch is digested, broken down to ogliosaccharides, what do these consist of
alpha limit dextrins
malotriose
maltose
(alpha-amylase used to break down, salivary and pancreatic glands)
enzymes associated with membrane digestion (ogliosaccharidases)
lactase
maltase
sucrase-isomaltase
alpha limit dextrins
stay connected since alpha-amylase cannot break branches adjacent to alpha-1,4 links / alpha-1,6 branches
all ogliosaccharidases can cleave alpha-1,4 linkages, what does this yield? which one works differently
glucose
lactase - breaks down lactose to glucose and galactose
which ogliosaccharidases can break the banching alpha-1,6 linkages of alpha limit dextrins
isomaltase
glut 2 is the faciliated diffusion for
all monosaccharides
which type of enzymes digest proteins first, what is also required sometimes to digest proteins
luminal enzymes (to amino) brush border enzymes (to amino) apical membrane transporters may carry them as peptides, then undergoes intracellular hydrolysis
or it can be carried as a peptide without intracellular hydrolysis
outline digestion in stomach (luminal enzymes)
HCl begins
Pepsin cleaves proteins to peptides (favours aromatic/larger AA- endopeptidase) (nonessential)
outline digestion in duodenum
5 pancreatic proteases either endo/exopeptidase
exo-at end/ C terminals
which of the pancreatic proteases are exopeptidase
Procarboxypeptidase A and B
product of pancreatic endopeptidases
ogliopeptides (2-6 amino acids)
why is there so may brush border enzymes
to compensate for the large diversity in AA
t/f brush border peptidases have a larger affinity for ogliopeptides
true
cytoplasmic peptidases primarily hydrolyse
di/tripeptides
how many sodiium dependant transporters are found at brush border, what do they do
how many are sodium independent
5
moves neutral amino acids up a conc gradient (hartnup disease)
2 (cystinuria)
basolateral has 5 different mechanisms, how many mediate efflux of amino acids and are Na+ independent, and how many mediate influx
3
2
(bidirectional)
PepT1 transports
di/tri/tetrapeptides via proton gradient at brush border
most amino acids are transported to cell by
sodium dependent transporters
why is brush border acidic
Na+/H+ exchanger,
