Hepatobiliary Function Flashcards
Dual blood supply to liver:
- Hepatic Artery (20-30%)
- Portal Vein (70-80%)
Main Functions of Liver:
- Bile production and secretion
- Metabolism of carbs, proteins and lipids
- Bilirubin production and excretion
- Detoxification of substances
Metabolic Functions of Liver: Protein Synthesis
- Synthesis of non-essential AAs
- Modification of AA for use in biosynthetic pathways for carbs
- Synthesis of almost all plasma proteins (ex. albumin, clotting factors)
- Conversion of ammonia (byproduct of protein catabolism) to urea
Liver failure can result in ______ which may lead to edema
Hypoalbuminemia
Bile Composition:
- Bile Salts (50%)
- Bile Pigments (2%) – ex. Bilirubin
- Cholesterol (4%)
- Phospholipids (40%) – ex. lecithin
- Ions
- Water
Bile Function:
- Vehicle for the elimination of substances from the body
- Solves the insolubility problem of lipids
Location of Bile Synthesis:
Hepatocytes (Liver)
Location of Dehyroxylation of Primary Bile Acids to Secondary Bile Acids:
Lumen of Intestines
Location of Conjugation of Secodary Bile Acids:
Liver
Newly synthesized bile acids and returning bile acids (recycled from enterohepatic circulation) are secreted into the ___ ___
Bile Canaliculi
Bile Canaliculi
- Located between Hepatocytes
- Move bile away from the center of the lobule and out to the bile duct
What occurs in the Duodenum?
Emulsification and digestion of fats
What occurs in the Jejunum?
Micelle formation and fat absorption
What occurs in the Ileum?
- Active absorption of conjugated form of bile acid (>90% of bile acids is absorbed into Portal blood here)
- Involved in recycling conjugated bile acids back to liver
Recycled bile acids return to liver in ___ circulation
Portal
What occurs in the Gallbladder?
Storage and concentration of bile between meals
Almost all bile formation is driven by:
Bile Acids (bile acid-dependent)
A small portion of bile is stimulated by ___ and is secreted from the ducts – known as ____ ___-___ or ___ ___
- Secretin
- Bile Acid-Independent
- Ductular Secretion
During the Interdigestive period, Gallbladder fills with bile:
- Gallbladder is relaxed
- Sphincter of Oddi is closed
On Eating, CCK-mediated:
- Contraction of the Gallbladder
- Relaxation of the Sphincter of Oddi
Uptake of Bile Salts across the Basolateral membrane of the hepatocytes is mediated by two types of systems:
(1) Na+-dependent transport protein, Sodium Taurocholate Co-Transporting Polypeptide (NTCP)
(2) Na+-independent transport protein, Organic Anion Transport Proteins
Rate of Bile Acid Synthesis & Secretion: Ileal Resection
- Do not have enough Bile Acid because it is not being reabsorbed in the Ileum
- Increased rate of bile acid synthesis
- Decreased rate of bile acid secretion
Rate of Bile Acid Synthesis & Secretion: Bile Acid Feeding/Excess
- Decreased rate of bile acid synthesis
- Increased rate of bile acid secretion
Cholesterol 7alpha Hydroxylase is inhibited by:
Bile Acids/Salts
Unconjugated bilirubin toxicity in the CNS damages:
- Neurons
- Astrocytes (increased release of inflammatory factors)
- Microglia (increased release of inflammatory factors)
- Oligodendrocytes (decreased myelin synthesis)
Biochemical Liver Function Tests: ALT
- Type of serum aminotransferase
- Very specific to the liver
Biochemical Liver Function Tests: AST
- Type of serum aminotransferase
- Nonspecific – found in other tissue besides the liver
What 3 Liver enzymes are commonly measured in the serum?
(1) ALT
(2) AST
(3) Alkaline Phosphatase
Elevated aminotransferases (ALT and AST) are primarily the result of:
Hepatocyte injury
Elevated Alkaline Phosphatase are primarily the result of:
Bile Duct injury (ex. Cholestasis)
Liver Function Tests: Albumin
- Synthesized exclusively in the liver
- Levels of this protein fall as the synthetic function of the liver declines with worsening cirrhosis
- Severe impairment of hepatocyte function is likely to reduce the level of this protein in the plasma
_____ is not specific to liver disease; it may also be seen in Kidney Glomerular Disease
Hypoalbuminemia
Liver Function Tests: Prothrombin Time (PT)
- Reflects the degree of hepatic synthetic dysfunction
- PT increases when hepatic synthesis of clotting factors is impaired
- PT increases as the ability of a cirrhotic liver to synthesize clotting factors diminishes
Saliva Secretion: Characteristics
- High [HCO3-]
- High [K+]
- Hypotonic
- Alpha amylase and lingual lipase
Saliva Secretion: Factors that Increase Secretion
PNS
Saliva Secretion: Factors that Decrease Secretion
- Sleep
- Dehydration
- Atropine
Gastric Secretion: Characteristics
- HCl
- Pepsinogen
- Intrinsic Factor (IF)
Gastrin Secretion: Factors that Increase Secretion
- HCl is increased by Gastrin, ACh and Histamine
- Pepsinogen is increased by PNS
Gastric Secretion: Factors that Decrease Secretion
- H+ in the stomach
- Chyme in the duodenum
- Somatostatin
- Atropine
- Cimetidine
- Omeprazole
Pancreatic Secretion: Characteristics of Aqueous Secretion
- High [HCO3-]
- Isotonic
Pancreatic Secretion: Characteristics of Enzyme Secretion
Pancreatic Lipase, Amylase and Proteases
Pancreatic Secretion: Factors that Increase Aqueous Secretion
- Secretin
- PNS
Pancreatic Secretion: Factors that Increase Enzyme Secretion
- CCK
- PNS
Bile Secretion: Characteristics
- Bile salts
- Bilirubin
- Phospholipids
- Cholesterol
Bile Secretion: Factors that Increase Secretion
- CCK – causes contraction of gallbladder and relaxation of sphincter of Oddi
- PNS
Bile Secretion: Factors that Decrease Secretion
Ileal Resection
