3.5 Gastrointestinal Physiology Flashcards
mucus of SI comes from what glands?
Brunner’s glands
fluid of SI is released from?
Crypts of Lieberkuhn
*like interstitial fluid
digestive enzymes of SI released by? Describe these enzymes***
Crypts of Lieberkuhn
**digestive enzymes perform the FINAL BREAKDOWN of nutrients; are brush border enzymes
what are the 3 main things secreted by SI?
mucus
fluid
digestive enzymes
What are brush border enzymes? Give examples?
disaccharidases, intestinal lipases, peptidases, enterokinase
* connected to WALL
function of disaccharidases?
split disaccharidase into monosaccharidases
function of intestinal lipases? another name for them?
splits triglycerides into Di and Mono
*another name is enteric lipases
function of peptidases?
final splitting of small peptides
what is the primary and most important regulator of SI secretion?
distention! Simply having food in there
What are the two forms of SI secretion regulation?
1) distension
2) neural (cephalic or gastric) can also stimulate SI secretion —minor importance
What is the secretino of liver?
bile
what is the most important component of bile?
bile salt; most important and most abundant to GI function (bilirubin can give important info regarding liver heath)
what is bile mostly composed of?
water
what is the components of bile?
water, electrolytes, cholesterol, lecithin, bile salts and bilirubin
bile salt synthesis?
cholesterol > cholic (chenodeoxycholic) acid + glycine or taurine > glycocholic or taurocholic conjugated bile acid
glycine or taurine used more in making of bile salts?
glycine
purpose of bilirubin?
liver incorporates bilirubin into bile after destruction of RBCs to get rid of it and gives bile its color. But since it is in the bile, it gives an indicator of liver heath (like how well it is breaking down RBCs and dealing with waste like bilirubin)
why do we need bile salts?
- transport
* fat breakdown (emulsification)
emulsification means?
fat breakdown
bile salts reabsorbed by?
portal vein
why is it important for bile salts to have a polar and nonpolar end?
b/c then it’ll be hydrophilic (polar= water soluble)) and hydrophobic! This means it is able to bind to fat AND easily transport fat in liquid
storage and concentration of bile in the?
gall bladder
what is the route of bile from liver TO the gall bladder?
1) hepatocytes (liver)
2) bile canaliculi
3) right and left hepatic duct
4) common hepatic duct
5) cystic duct
6) gall bladder
common hepatic duct and cystic duct join to form the?
common bile duct
between meals, is the sphincter of Oddi closed or open? What does it do?
closed
*it controls release of bile, so between meals when we don’t need bile, it is closed to store bile
***what 4 things does CCK do?
1) stimulate pancreatic enzymatic secretions
2) inhibit stomach/gastric secretions and motility
3) relax sphincter of Oddi to allow bile flow
4) stimulate gallbladder contractions
what is another name for sphincter or Oddi?
hepatopancreatic sphincter
gall stones are mostly? caused by an increase?
cholesterol (concentration of bile/fat)
*caused by an increase of bile
what is bile-stasis?
bile that sits in gall bladder for a long time
what are common factors leading to an increase in bile concentration?
1) too much cholesterold in bile
2) too much water absorption from bile
3) too much absorption of bile slats and lecithin
4) GB epithelium inflammation
what are choleretics?
things that make you secret bile
- chole= bile
- retics= secret
bile is continuously secreted by?
hepatocytes
what regulates bile secretion?
1) bile continuously secreted by hepatocytes
2) choleretics (increase bile secretion)
give examples of choleretics?
- vagal stimulation
- increase hepatic blood flow
- presence of bile salts (increase bile flow and decrease formation of new bile salts)
what regulates gall bladder emptying and bile release?
1) fat in SI > CCK > GB contraction an sphincter of Oddi relaxation
2) peristalsis of SI also aids release by RELAXING the sphincter of Oddi
* **obviously, sphincter of Oddi most important
what are the two functions that bile salts perform?
1) emulsification of fat into small particles that can be digested by enzymes
2) transportation anf absorption of digested fat
what does lecithin do?
same thing as bile salts but is a smaller molecule
what happens to surface tension when bile salts/lecithin bind fat?
surface tension DECREASES and fat breaks down into smaller units called EMULSION DROPLETS
order from largest to smallest: emulsion droplets, fat globule or micelle
fat globule
emulsion droplet
micelle
what are emulsion droplets?
smaller than fat globule
*contain bile salts or lecithin
what are micelles?
bile salts + pancreatic lipase
*they are small fat globules (glycerides. free FA, phospholipids, cholesterol) surrounded by bile salts
micelle is like a ______ but smaller
emulsion droplet
Micelles play an important role in?
the transport of fats b/c they are smaller and fats don’t tranel well in solution without help
***when are bile salts absorbed?
in the ilium AFTER they have released their fat in duodenum
describe the enteroheptic circulation of bile salts? where do they go?
- 95% of bile salts are absorbed in distal SI and recirculated to liver (via portal vein) and secreted again
- 5% are excreted in feces
why salivate before puking?
puke is very acidic!
So you’ll salivate and make lots of bicarb as a buffer before all that acid goes through the oral cavity
