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Functions of the Liver in the Gastrointestinal System

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40 Questions

What is a primary function of the liver in relation to the blood from the gastrointestinal tract?

To serve as a filter between the blood from the gastrointestinal tract and the blood in the rest of the body

What is the primary source of blood that reaches the liver?

Portal vein

Where does the bile formed in the liver eventually drain into?

Intestine

What is the average time it takes for blood to pass through the liver lobule from the portal venule to the central hepatic vein?

8.4 s

What is the purpose of the sinusoids in the liver?

To allow for efficient exchange of substances between the blood and hepatic cells

What happens to the blood during its passage through the hepatic plates?

It is extensively modified chemically

What is the reason for portal pressures not increasing linearly with portal flow?

To prevent fluid loss from the highly permeable liver under normal conditions

What is the result of increased hepatic pressures in disease states?

Accumulation of fluid in the peritoneal cavity as ascites

What type of nerve fibers innervate the intrahepatic portal vein radicles?

Noradrenergic vasoconstrictor

What happens to the portal vein radicles when systemic venous pressure rises?

They are dilated passively

What is the result of diffuse noradrenergic discharge in response to a drop in systemic blood pressure?

Constriction of the intrahepatic portal radicles

What happens to the blood flow through the liver during heart failure?

It bypasses most of the liver

What is the primary function of the enzyme glucuronyl transferase in the liver?

To conjugate bilirubin to glucuronic acid

What is the main difference between free bilirubin and bilirubin glucuronide in terms of solubility?

Bilirubin glucuronide is more water-soluble

Where is the enzyme glucuronyl transferase primarily located in the liver cell?

Smooth endoplasmic reticulum

What is the role of multidrug resistance protein-2 (MRP-2) in the liver?

To transport bilirubin glucuronide into the bile canaliculi

What is the fate of most of the bilirubin glucuronide produced in the liver?

It is transported into the bile ducts

What is the significance of the binding of bilirubin to albumin in the blood?

It reduces the excretion of bilirubin in the urine

What is the primary driving force for the initial formation of canalicular bile?

Active secretion of bile acids

What is the approximate ratio of bile acids:phosphatidylcholine:cholesterol in canalicular bile?

10:3:1

What happens to the tight junctions between adjacent hepatocytes during bile formation?

They remain permeable to allow passive diffusion

What is the consequence of deviations from the normal bile acids:phosphatidylcholine:cholesterol ratio in canalicular bile?

Cholesterol precipitation and gallstone formation

What is the fate of conjugated bilirubin in bile duct obstruction?

It regurgitates into the blood

What is the function of phosphatidylcholine in bile?

It forms mixed micelles with bile acids and cholesterol

What is the main function of the gallbladder in relation to bile?

To store and concentrate bile

What is the approximate percentage of solids in gallbladder bile?

10-12%

What happens to the sodium ion concentration in bile as it becomes more concentrated?

It increases

What is the pH of gallbladder bile compared to hepatic duct bile?

It is less alkaline

What is the result of clamping the bile duct and cystic duct?

Intra-biliary pressure increases and bile secretion stops

What is the composition of hepatic bile in terms of water content?

97% water

What is the main reason for the reabsorption of some bile pigments and urobilinogens in the portal circulation?

The action of bacteria in the intestine on bilirubin

At what level of plasma bilirubin is jaundice typically detectable?

2 mg/dL (34 μmol/L)

What is the effect of hemolytic anemia on bilirubin levels in the blood?

Excess production of bilirubin

What is the fate of small amounts of urobilinogens that enter the general circulation?

They are excreted in the urine

What is the main difference between conjugated bilirubin and urobilinogens?

Urobilinogens are formed in the intestine

What is the effect of intrahepatic or extrahepatic bile duct obstruction on bilirubin levels?

Disturbed secretion of conjugated bilirubin into the bile canaliculi

What is the role of the intestinal mucosa in the reabsorption of bilirubin and urobilinogens?

It is impermeable to conjugated bilirubin but permeable to unconjugated bilirubin

What is the significance of the free bilirubin level in the blood?

It rises in cases of disturbed intracellular protein binding or conjugation

What is the result of the enterohepatic circulation of bilirubin and urobilinogens?

Reabsorption of some bile pigments and urobilinogens into the portal circulation

What is the primary cause of hyperbilirubinemia in the blood?

All of the above

Test your knowledge of the liver's role in filtering blood from the gastrointestinal tract and its functional anatomy. Learn about the portal vein, sinusoids, and hepatic cells. Evaluate your understanding of the liver's importance in the body.

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