3.a Intestinal phases Flashcards
In descending order where most digestion and absorption takes place:
Duodenum
Jejenum (does not secrete)
Ileum
Duodenum, jejenum, ileum
What kind of signals does the duodenum give when food enters it?
-> Contents entering the duodenum initiate signals that delay gastric emptying/contractions.
-> Increased amplitude of contractions of pylorus and duodenum
Duodenual cluster unit does not contain..
liver
Does contain
Duodenum, stomach, biliary system, exocrine pancreas
Sphincter of Oddi is the entry point for..
pancreatic juices and bile
(liver also attached)
Pancreas is divided into..
Acinus
Ductule
How does the pancreas work?
Acinus: Granules filled with “pro-enzymes” stored. Not active yet. Activated by neurones or hormones and then released into the..
Ductule: Flushed into small intestine upon adding of bicarbonate, activated by for example secretin.
Duodenal cluster unit regulates entry of chyme, titrates exocrine secretions and mixes them.
Duodenal wall: osmolarity and nutrient meter. What does it do?
Activate CCK + nerves
Regulates Bile from biliary secretion
Regulates enzymes from pancreatic juice and gastric chyme.
Determine the flow from stomach into duodenum.
Duodenal cluster unit regulates entry of chyme, titrates exocrine secretions and mixes them.
Duodenal wall: pH meter. What does it do?
Secretes secretin, which regulates bicarbonate from biliary secretion and from pancreatic juice
What does the duodenal wall secrete itself?
H2O + HCO3- (bicarbonate) secretion
Why is bicarbonate very important?
Because it neutralizes the gastric acid in the small intestine (among other factors)
Name other factors that affect pH in the small intestine.
Gastric acid (H+ input)
H+ absorption
Buffers
Protein
Bile acids
Fatty acids
What do S cells do (sensor cell)?
They secrete the secretin, which adjusts the amount of bicarbonate released into the lumen of the duodenum.
They are in the duodenal mucosa and sensor the pH.
Does it matter if your meal is hyper or hypotonic for the pH in the duodenum?
No, in the duodenum they are all normalized to the isotonic situation.
What check-up system is used in the small intestine?
The monitor peptide is used (released in the duodenum with digestive enzymes)
When sensing cells sense this peptide, they release CCK hormones.
What does trypsin do with monitor peptide?
It digests it.
How is CCK ( Cholecystokinin) then released in the latter part of the intestine?
CCK-RP (CCK-releasing peptide)
activates release of CCK. However also get degraded. No CCK activation anymore.
p.22
Via what does the CCK convey its messages?
DVC
Effects of CCK?
Gall bladder contraction (fatty acid stimulation)
Relax sphincter of Oddi
Decreased acid secretion
Decreased gastric emptying
Increased pancreatic enzyme
What are the major solid components of bile?
Bile acids
Bile acids are synthesized by … and stored in …. and recirculated via …
Liver
Gallbladder
Portal vein of intestine > liver > reused
Pancreatic secretions are stimulated by..
Neural and humoral mechanisms (CCK)
Where is CCK secreted / located?
CCK is also positioned at top of acinus of pancreas. Stimulates pancreatic enzyme secretion
Most of the enzymes secreted by pancreas are..
pro-enzymes (not activated)
Enzymes enter the lumen. At the lumen, you have microvilli which contain enzymes as well:
Enterokinases
What is required for activation of some pancreatic digestive enzymes?
Brush border enterokinase and luminal trypsin
p.23
Duodenal passage alters the physical characteristics of the meal. Name some of pre duodenum vs at duodenum
Antrum:
< 2mm
emulsified triglyceride
hyperosmotic
pH 5-6
protonized protein
indigestible fiber
Duodenum:
macromolecules
micellar lipids
isoosmotic
pH 7
solubized protein
indigestible fiber
Protein digestion takes place during what phases?
Gastic + intestinal phase
CCK is a hormone that stimulates…
.. pancreatic bicarbonate secretion
.. bile production
.. release of pancreatic enzymes
Which is true?
release of pancreatic enzymes
Enterokinase is an exo/endo peptidase. It cleaves peptidases (trypsinogen -> trypsin)
Endo
Of which organs can the blood be slightly acidic?
pancreas, gall bladder, small intestine
Brush border enzymes play a large role in having last step of digestion (e.g. degradation of oligopeptides into amino acids).
Only nutrient where no ‘final digestion’ is needed = ?
Lipids
