L24: Mucosal Absorption Flashcards
once food is in an absorbable size, it is translocated from the lumen of the intestine to…
the extracellular space of the gut for further processing and distribution
the process of translocating basic molecules from the interstitial lumen through the epithelial cells of the intestine into the vascular system
absorption
T/F: the end products of carbohydrate and protein digestions are hydrophilic
True
how is glucose transported across the basolateral membrane
by facilitated diffusion (via transport protein, GLUT-1)
movement of glucose through the basolateral space is driven by…
diffusion
what is the most important active transporter
Na/K pump
what is an important secondary active transporters
Na/Glucose co transporter; uses the Na gradient
transcellular absorption
ions follow electrochemical gradient through ion channels in the apical membrane
paracellular absorption
ions follow electrochemical gradient and osmotic pressure through tight junctions
tight junctions are freely permeable to water and small ions
facilitated diffusion
spontaneous passive trasnport of molecules or ions across membrane via specific membrane integral proteins
glucose is transported across the basolateral membrane by ________ diffusion
facilitated via GLUT-1; dependent on glucose gradient
the Na+ glucose coupled transport stimulates water absorption by ______
solvent drag
oral rehydration salts exploit what transporter
SGLT-1 co transporter; remains active due to strong Na-gradient
disorders of carbohydrate digestion and absorption are mostly due to…
enzyme deficiencies that prevent breakdown of carbohydrates to an absorbable form
unabsorbed carbohydrates hold water osmotically and cause _____ diarrhea
osmotic
solute driven water loss
95% of ingested fat is removed by the ….
small intestine
why package lipids into small vesicles at the lumen of GI tract and inside the cell
hydrophobic but need to be transported in watery enviornment
micelles enter the enterocyte cell and are repackaged into…
Chylomicrons: core of triglyceride and cholesterol surrounded by phospholipase and apoproteins
what are chylomicrons
transport vehicles for lipids in lacteals
water soluble chylomicrons
coat of phospholipids, triglycerides, proteins and contnet of triglycerides, cholesterol ester
what is the importance of apoproteins
they are structural components of liporprotein particles; serve as ligands for cell surface receptors and as cofactors for enzymes
what happens in the absence of apoproteins
large quantities of triglycerides accumulate in enterocytes
chylomicrons are taken up by…
lacteals - lymphatic vessels in villi that take up lipids
where do lacteals drain into
cisterna chyli (abdominal lymphatic duct), further into the thoracic lymphatic duct and into the internal jugular vein
bile acids remain in the _______ lumen and are _____
intestinal
recycled
where are bile acid transporters (Na-bile acid cotransporter) located
ileum
bile acids are synthesized from ________ in the _________
cholesterol
liver
bile acids are released into the _________ and flow through the _________ lumen where it emulsifies lipids
duodenum
intestinal
lipids are primarily absorbed by ________ in the ________
enterocytes
jejunum
a large % of bile acid is reabsorbed and returned to the _______ via the ______
liver
portal system (portal vein)
if the liver doesn’t recycle bile acids, where will they show up
in the plasma
complete or partial damage to the portal blood flow will cause _______ elevation because they bypass the liver (portosystemic shunt)
blood bole acid elevation
acquired liver shunts can result from..
liver disease
liver shunts can be _____ or develop from liver diseases
congenital
what size and breed(s) are most susceptible to congenital extrahepatic liver shunts
small and toy breeds
large breed dogs are more likely to have what kind of liver shunt
intra-hepatic
accumulation of toxins and metabolic waste products from a liver shunt ca lead to hepatic _______
encephalopathy
clinical signs of liver shunts
- poor growth / development
- neurologic & behavioral changes
- increased thirst and frequcny of urination
- vomiting
- accumulation of toxins and metabolic waste leading to hepatic encephalopathy
in hepatic encephalopathy, gut-derived ______ substances accumulate such as _______
neurotoxic
Ammonia (can cross BBB)
what is the bile acid test
liver function test
indicates the degree of inflammation or damage
fast for 12 hrs
collect preliminary blood sample
small meal
2 hours after meal, blood sample collected
blood samples are tested for levels of bile acids
what would you expect to see in a normal bile acid test
low initial and low post meal levels of bile acids
if a patient has an elevated resting sample from the bile acid test, what does this mean
bile acids are remaining in circulation –> liver disease, portosystemic shunt, impaired gall bladder, gall stones, etc
if you do the bile acid test and get normal low resting BA levels but elevated BA levels post meal, what does this tell you?
bile acids are slowly reabsorbed and escape into the systemic circulation
the liver is able to handle BA between meals but not the load of substance that arrives after a meal
