Final Exam GI Physiology: Liver Flashcards
Most of the hepatic blood supply is ____________ and delivered by the hepatic portal vein.
hypoxygenated
The hepatic artery delivers ________ blood to the liver.
oxygenated
How does the liver metabolize carbohydrates?
Uses carbs for glycogenesis, glycogenolysis, and GLUconeogenesis
How does the liver metabolize lipids?
Beta-oxidation of fatty acids
FA and TAG synthesis
Synthesis and export of: ketones, cholesterol, and lipoproteins
Converts carbs and AAs into triacylglycerol
How does the liver metabolize proteins?
Deamination and transamination
Plasma protein synthesis of:
Albumin, a & B globulins, coagulation factors, complement proteins, plasma antiproteases
NH3 uptake, urea and glutamine synthesis
What does the liver do with vitamins?
Stores them! A, D, and B12
What does the liver do with iron?
Stores it!
What is a Phase I Transformation reaction?
A biotransformation that provides polar groups for reactions.
What is a Phase II Transformation reaction?
A reaction that conjugates the products of Phase I reactions to produce a strong acid.
What do Phase I reactions do to the toxicity of a compound?
Increases OR decreases the toxicity
Bile is produced by which organ?
The liver
What are the 4 functions of bile?
- Emulsification of lipids
- Excretion of wastes (bilirubin, drugs, hormones)
- Protection (IgA)
- Protection (bile acids kill bacteria)
What are the 6 components of bile?
- Electrolytes (with water)
- Phospholipids (mostly lecithans)
- Cholesterol
- Bile acids
- IgA
- Biotransformation waste products
How does the liver make primary bile acids?
It conjugates cholesterol and amino acids to make bile acids
Where are primary bile acids converted into secondary bile acids?
In the small intestine
What does high plasma [bile acids] indicate?
Liver disease, compromised bile flow, accumulation of bile, and backflux of bile into circulation
Where are bile acids reabsorbed?
Ileum (99% absorbed here)
How do bile acids get to the liver?
Through the portal vein
Describe the route of bile acids
Liver–> Bile duct –> Intestine –> Portal vein –> Liver
What is enterohepatic circulation?
The route that bile acids take starting and ending at the liver
What cells are majorly responsible for the degradation of red blood cells and where are they found?
Macrophages found in the spleen degrade RBCs
After an RBC is degraded, what happens to the hemoglobin?
It is reduced to biliverdin and reduced further by macrophages, then released as unconjugated bilirubin
Is unconjugated bilirubin toxic?
YES!
Can unconjugated bilirubin diffuse through cell membranes?
YES!
What plasma protein has a high affinity for unconjugated bilirubin?
Albumin
Why is it advantageous that albumin has a high affinity for unconjugated bilirubin?
Because unconjugated bilirubin is toxic and can pass through cell membranes. When albumin binds to it, a complex is formed. This complex CANNOT pass through cell membranes.
Hepatocytes have albumin receptors which allows for rapid uptake of _________ ________.
unconjugated bilirubin
How does unconjugated bilirubin become conjugated bilirubin?
It is acted on by glucuronyl transferase (a conjugating enzyme that performs a Phase II rxn). This produces conjugated bilirubin.
Is conjugated bilirubin able to diffuse across cell membranes?
NO, it’s water soluble and not bound by albumin
Conjugated bilirubin is also known as ________ bilirubin.
DIRECT
Unconjugated bilirubin is also known as _____ bilirubin.
INdirect
Both forms of bilirubin are colorful _________.
pigments
What happens when plasma [bilirubin] rises?
A yellow color is imparted and Jaundice or Icterus occurs
What substance is secreted into the bile canaliculi and becomes a component of bile?
Conjugated bilirubin
How does conjugated bilirubin get into the small intestine?
Through the bile duct
What happend to conjugated bilirubin when it is in the lumen of the small intestine?
Acted on by bacteria that cleave off the glucuronide residue to make free bilirubin.
What is free bilirubin reduced to?
Urobilinogen and Stercobilinogen (these terms refer to the ultimate route of excretion- urinary or fecal)
How does yellow bile pigment end up in the urine?
Intestinal bacteria removes the gluconuride conjugate residue making the molecule MORE lipid soluble. This allows urobilinogen to be absorbed by the terminal ileum and large intestine. During transfer to the liver via the hepatic portal vein, some urobilinogen escapes and is excreted by the urinary route.
How do bile acids enter the bile canuliculi?
By using membrane pumps that use ATP
The presence of bile acids in the canuliculi draws water by __________ and electrolytes by _________.
Osmosis; solvent drag
What are cholangiocytes?
bile ductular cells
How are bile ductular cells like pancreatic ductular cells? What is the result?
They both exchange HCO3- for Cl- which increases the pH of bile (makes it more basic)
What stimulates bile and pancreatic ductular cells?
Secretin
What are choleliths?
Gall stones
