(F) L3: Liver Function Tests (Introduction) Flashcards
Which liver lobe is larger than the other?
Right
- A large organ that weighs 1.2 to 1.5 kg in a healthy adult
- The chief metabolic organ that metabolizes nutrients and detoxifies blood
- Located at the right upper quadrant of the abdomen, beneath and attached to the diaphragm
- Has a right and left lobe divided by the falciform ligament
Liver
- This is located near the liver where it is connected via the common bile duct
- Waste products from the liver, bile salts, bile acids, and bilirubin go into this organ
- This is responsible for the storage of bile
Gallbladder
The liver’s blood supply comes from what 2 blood vessels?
Also give the percentages of how much blood they supply
- Hepatic artery (25%; oxygenated)
- Portal vein (75%; rich in nutrients)
The liver receives how many mL of blood per minute?
15mL
Once the hepatic artery and portal veins reach the hepatic sinusoids, where does the blood go in order to return to the general circulation?
Central canal
Toxins that were removed from the blood will be excreted via what passage to the gallbladder?
(2 answers)
Bile canal and bile duct
Note: The waste products will go into the feces
This liver cell type is responsible for the metabolism and synthesis of proteins
Hepatocytes
This liver cell type is a macrophage which are important for phagocytosis (for immunity)
Kupffer Cells
Functions of the Liver
Carbohydrates are stored in the liver in the form of glycogen and vitamins
Storage
Functions of the Liver
- Refers to the processing of carbohydrates, lipids, and proteins
- Important for the processes of glycogenesis, glycogenolysis, and gluconeogenesis
Metabolism
Functions of the Liver
Most plasma proteins and clotting factors are produced by the liver hence why the proteins will decrease in number whenever there is liver damage
Synthetic
Functions of the Liver
- Transamination leads to the production of ketoacids (Kreb’s cycle) and ammonia (Urea cycle)
- Important for the removal of toxic substances such as alcohol, drugs, and ammonia to urea
Detoxification
Functions of the Liver
- Has something to do with the biliary system (bilirubin and bile)
- Bilirubin (B1: originally unconjugated) will be coupled to a protein to make it conjugated (B2)
Conjugation/ Excretory and Secretory
Excretory and Secretory Function
- aka GALL, a dark green or yellowish brown fluid
- Produced by the liver, stored in the gallbladder, and released in the duodenum
- Helps in lipid digestion, emulsification of dietary lipids, and hydrolysis of TAGs
- Is composed of water, fatty acids, cholesterol, bile acids/salts, and bilirubin
Bile
Excretory and Secretory Function
Bile acid vs. Bile salt:
1. The unconjugated form
2. The conjugated form
- Unconjugated - Bile acid
- Conjugated - Bile salt
Note: Salts are also acids but only conjugated with amino acids
Excretory and Secretory Function
These are waste products of cholesterol metabolism which are the primary components of bile that facilitate the digestion and absorption of lipids
Bile acids/Bile salts
Classification of Bile Acids and Bile Salts
Primary or Secondary?
1. Cholic acid and Chenodeoxycholic acid
2. Deoxycholic acid, Lithocholic acid, and Ursodeoxycholic acid
- Primary
- Secondary
Classification of Bile Acids and Bile Salts
Primary or Secondary?
Not yet exposed to the normal flora of the intestines which utilize these bile acids/salts
Primary
Classification of Bile Acids and Bile Salts
Primary or Secondary?
Already exposed to the normal flora of the intestines
Secondary
Classification of Bile Acids and Bile Salts
The primary and secondary classification in the lab is used to differentiate between what 2 conditions?
Biliary Obstruction and Liver Cirrhosis
Classification of Bile Acids and Bile Salts
What condition?
Increased ratio of primary and secondary bile salts/acids
Biliary Obstruction
Classification of Bile Acids and Bile Salts
What condition?
Decreased ratio of primary and secondary bile salts/acids
Liver Cirrhosis
Excretory and Secretory Function
- A pigment that imparts a yellow color to the bile (different from biliverdin which is green)
- Approximately 200-300mg of this is produced per day
- A metabolic waste product of heme breakdown (80% from RBCs)
- Can be used to assess the conjugation and excretion function of the liver
Bilirubin
Excretory and Secretory Function
What type of bilirubin is found in the bile?
Conjugated (B2)
Excretory and Secretory Function
Bilirubin must be excreted from the body in what form?
Urobilinogen (therefore if bilirubin is elevated, there must be a problem with the liver)
Bilirubin Synthesis Pathway
Step 1: Heme is converted into what using the heme oxygenase enzyme?
Biliverdin
Bilirubin Synthesis Pathway
Step 2: Biliverdin is converted into what with the help of biliverdin reductase?
Unconjugated Bilirubin (B1)
Bilirubin Synthesis Pathway
- This is water insoluble
- Is aka “pre-hepatic, indirectly measured, and slow reacting” bilirubin
Unconjugated Bilirubin (B1)
Bilirubin Synthesis Pathway
Step 3: Unconjugated Bilirubin (B1) needs a transport protein to reach the liver (since it is water insoluble) which is what?
Albumin
Bilirubin Synthesis Pathway
Step 4: Once B1 enters the hepatocytes, it will bind to what proteins before going to the smooth endoplasmic reticulum?
(3 answers)
- Y proteins
- Z proteins
- Ligandin
Bilirubin Synthesis Pathway
In what hepatocyte organelle does bilirubin conjugation occur in?
Smooth ER
Bilirubin Synthesis Pathway
Step 5: This enzyme helps in the conjugation of B1 into B2, what is it?
Uridylphosphate Glucuronyl Transferase (UDPGT)
Note: It adds 2 glucuronic acids to B1
Bilirubin Synthesis Pathway
- This is water soluble
- Is aka “directly measured and prompt reacting” bilirubin
Conjugated Bilirubin (B2)
Bilirubin Synthesis Pathway
What is the other name for B2 with respect to the addition of 2 glucuronic acids?
Diconjugated/Diglucuronide Bilirubin
Bilirubin Synthesis Pathway
If there is biliary obstruction, what can we expect with the levels of B1 and B2?
B1 is normal while B2 is elevated
Bilirubin Synthesis Pathway
Step 6: Once bile is released to this organ, it will aid in the digestion and emulsification of fats
Intestines
Bilirubin Synthesis Pathway
Step 7: Once B2 encounters the normal flora found in the GIT, it will be converted to what?
Urobilinogen
Bilirubin Synthesis Pathway
Step 8: Approximately 80% of urobilinogen is excreted where in the form of urobilin/stercobilin?
Feces
Bilirubin Synthesis Pathway
TOF: Urobilinogen is originally colorless but will produce color once reduced (yellow for urobilin and brown for stercobilin)
False (oxidized, not reduced)
Bilirubin Synthesis Pathway
This manifestation of biliary obstruction refers to when one’s stool is colorless due to decreased urobilinogen
Steatorrhea
Bilirubin Synthesis Pathway
Step 8: The remaining 20% of urobilinogen is recirculated into what cycle?
Extrahepatic/Enterohepatic Cycle
Bilirubin Synthesis Pathway
Step 9: A small portion of the 20% recycled bilirubin will enter the systemic circulation which will be excreted at a rate of 1-4mg a day in what specimen?
Urine
HPLC Bilirubin Fractions
The unconjugated bilirubin (B1)
Alpha-bilirubin
HPLC Bilirubin Fractions
The monoglucuronide/monoconjugated bilirubin
Beta-bilirubin
HPLC Bilirubin Fractions
The diglucuronide/diconjugated bilirubin (B2)
Gamma-bilirubin
HPLC Bilirubin Fractions
- A conjugated form that is irreversibly bound to albumin (biliprotein)
- Formed when there is prolonged elevation of conjugated bilirubin in biliary obstruction
Delta-bilirubin
HPLC Bilirubin Fractions
This formula gives what product?
Total Bilirubin - (Direct Bilirubin [B2] + Indirect Bilirubin [B1])
Delta-bilirubin
