GI/ Liver Flashcards
what cells secrete histamine
ECL cells
enterochromaffin cells
What gut cells secrete intrinsic factor and what does it do
parietal cells, aids in Vit B12 absorption for iron absorption
what nerve is stimulated in the cephalic and gastric phases and what does it do?
vagus, gastric acid secretion
What happens during the gastric phase of digestion
Gastrin is released from G cells to stimulate Parietal cell release of HCl and histamine
at what pH is gastric acid secretion halted
<2.5
What increases gastric contractions
gastrin and distention
how is BMI calculated
weight/height^2
what is the average basal metabolic rate
24kcal / kg / day
which vitamins are fat soluble
A, D, E, K, absorbed with fats in the ileum
which vitamins are not fat soluble? where are they absorbed?
B C, in the jejunum….apart from B12 which is the terminal ileum with intrinsic factor
where is most water absorbed
jejunum ~80%
where are bile salts reabsorbed in the gut
ileum
what is a cause of K+ loss
diarrhoea
what fetal tissue forms the foregut
endoderm
what are kupffer cells, where are they found, and what blastocyst layer are they derived from?
macrophages of the liver are found in the sinusoidal lumens and formed from mesoderm
what is a lobule
a hexagonal functional unit of the liver
central vein
portal triads branch at each corner
describe the histology of the liver
Sinusoids lined by fenestrated epithelium.
-contains kupffer cells
They receive blood from Hepatic artery and portal vein.
They are separated from the hepatocytes by the space of Disse.
Bile canaliculi between hepatocytes - tight and gap junctions and desmosomes - actin pumps bile towards ducts.
What is stored in the liver?
Iron - as ferritin
Copper - RBC formation + in plasma bound to ceruloplasmin
Glycogen - stores last around 12 hours
Vitamins - Fat soluble - A D E K
- also B12Name the plasma proteins produced in the liver
Albumin
Fibrinogen
Globulin
What is a Xenobiotic?
foreign chemical not normally found or produced in the body and cannot form energy.
What is a liver phase 1 reaction
transforms a substance from one type to another
oxidation or hydrolysis
what is a phase 2 liver reaction
Conjugation
Excretion
Glucuronidation (addition of glucuronic acid) - makes things hydrophilic
Glucose-Alanine cycle
Proteins move from muscles to the liver when glycogen stores are low.
Alanine can be converted to pyruvate in the liver, while pyruvate is converted to alanine in the muscle.
explain the urea cycle
Removes excess nitrogen
only produces urea
Arginine > Ornithine > Citrulline
Urea cycle
-what gets added to arginine, and what does it produce?
Arginine + H2O (Arginase) > Urea + Ornithine
Urea cycle
-what gets added to Ornithine, and what does it produce?
Ornithine + Ammonia + CO2 > Citrulline
Urea cycle
-what gets added to Citrulline, and what does it produce?
Citrulline + Ammonia > Arginine
What does excess ammonia do to the body?
Neurotoxic
Requires lots of water to excrete > dehydration
describe fatty acid absorption
- fats enter intestine
- emulsified by bile to form Micelles
- Digested into free triglycerides
- absorbed into cells
- Golgibody combines them with cholesterol to form chylomicrons
- move into lacteal system
- moved to blood stream
- moved to liver
- moved to adipocytes as VLDL
where is LDL formed
Plasma
Where is HDL formed
Liver
Where is biliverdin produced and using what enzyme
In the spleen haem is broken down by Haem Oxygenase
How is Biliverdin converted to unconjugated bilirubin
In the liver by Biliverdin reductase
How is bilirubin conjugated
Glucuronyltransferase enzyme in the liver
what proportion of conjugated bilirubin is reabsorbed in the gut? What happens to it?
10% converted to urobilin in the gut and reabsorbed - excreted by kidneys or added to bile
When does insulin secretion begin?
20 weeks
Where is insulin produced?
Beta cells in the pancreatic islets of Langerhans.
Most of the tail is made of these islets, while the body and head are a larger mixture of exocrine and endocrine cell functions
what pancreatic cells produce what?
Alpha - glucagon
Best - Insulin
Delta - Somatostatin
What are the acini of the pancreas
exocrine secretory units with no visible lumen
what type of epithelium lines the pancreatic ducts?
simple columnar
what does aldehyde fuchsin stain?
Beta cells of the pancreas blue
What enzymes cleaves peptide bonds?
trypsin (active), chymotrypsin (inactive precursor), and elastase
What enzymes cleave amino acids from their protein C-terminals
carboxypeptidase
what proportion of the pancreas is exocrine (by mass)?
90-95%
what is a zymogen
inactive precursor enzyme
What is secretin released in response to?
Acid
What is CCK released in response to?
Fats, Protein, and nervous input
what stimulates HCO3- (bicarb) to be secreted
Secretin
What do PP cells do and where are they?
Pancreatic islets of langerhans
opposite of CCK - relaxes gallbladder, stops enzyme secretion, stops bicarb secretion
