Hepatic Circulation and Liver Structure

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Questions and Answers

What series of structures will bile salt travel through in order to emulsify fats in the small intestine?

  • i, iii, vii, viii (correct)
  • ii, iii, vii, viii
  • ii, vi, vii, viii
  • ii, iv, v, ix
  • i, iv, v, viii

What series of structures will blood travel through in order to supply the liver with oxygen and leave the liver with carbon dioxide?

  • ii, iii, vi, vii, ix (correct)
  • iii, vi, v, viii, ix
  • ii, iii, v, vii, ix
  • iii, v, vi, vii, ix
  • ii, v, vi, vii, ix

Name the two types of blood circulation that occur in the liver.

Hepatic artery and hepatic portal vein

The liver is composed of four lobes.

<p>True (A)</p> Signup and view all the answers

What are the two main functions of the hepatocytes?

<p>Metabolism and storage</p> Signup and view all the answers

The liver can store glycogen in the fed state.

<p>True (A)</p> Signup and view all the answers

The liver can synthesize glucose from noncarbohydrates like amino acids, glycerol, and lactic acid.

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The liver can synthesize lipoproteins.

<p>True (A)</p> Signup and view all the answers

The liver can synthesize bile.

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What is the main function of kupffer cells?

<p>Kupffer cells are phagocytic cells that remove defective blood cells, bacteria, and other foreign materials from the blood circulating through the liver.</p> Signup and view all the answers

The liver is involved in the interconversion of essential amino acids into nonessential amino acids.

<p>True (A)</p> Signup and view all the answers

The liver converts ammonia into urea

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The liver converts unconjugated bilirubin into conjugated bilirubin.

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Cholecalciferol, a steroid intermediary produced by exposure to ultraviolet light is metabolized to vitamin D by the hepatocytes.

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The liver detoxifies toxic medications and compounds absorbed by the Gl tract.

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The liver is responsible for the half-life of hormones by breaking them down.

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The liver only stores glycogen.

<p>False (B)</p> Signup and view all the answers

What are the two main characteristics used to assess liver function?

<p>Protein-synthesizing capacity and excretory capacity.</p> Signup and view all the answers

Elevated serum liver enzymes is indicative of liver damage.

<p>True (A)</p> Signup and view all the answers

What are the two enzymes that catalyze the transamination of their respective amino acids?

<p>Aspartate aminotransferase (AST) and alanine aminotransferase (ALT)</p> Signup and view all the answers

The half-life of a compound is the amount of time taken to remove half the concentration of a compound from the blood.

<p>True (A)</p> Signup and view all the answers

AST and ALT have relatively short half-lifes.

<p>False (B)</p> Signup and view all the answers

The AST:ALT ratio can help diagnose the condition or stage of liver disease.

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An AST:ALT ratio below one (<1) is indicative of non-alcoholic fatty liver disease or late-stage viral hepatitis.

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An AST:ALT ratio above two (>2) is indicative of alcohol-related liver damage.

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An AST:ALT ratio above five (>5) is indicative of a condition unrelated to the liver, like myocardial infarction or rhabdomyolysis.

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Albumin and prothrombin can also act as proxies for liver health, whereby drops in either protein indicate liver dysfunction.

<p>True (A)</p> Signup and view all the answers

Name the three indicators of the liver's excretory capacity.

<p>Serum bilirubin, Gamma-glutamyltransferase (GGT), and alkaline phosphatase.</p> Signup and view all the answers

Unconjugated bilirubin is a byproduct of heme breakdown.

<p>True (A)</p> Signup and view all the answers

The liver takes up unconjugated bilirubin and converts it into conjugated bilirubin, a more soluble form.

<p>True (A)</p> Signup and view all the answers

Elevated levels of unconjugated bilirubin (without a rise in conjugated bilirubin) might indicate hemolysis.

<p>True (A)</p> Signup and view all the answers

Elevated levels of conjugated bilirubin (without a rise in unconjugated bilirubin) might indicate cholestasis.

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Serum gamma-glutamyltransferase (GGT) is elevated in cholestasis, viral hepatitis, and non-alcoholic liver disease.

<p>True (A)</p> Signup and view all the answers

Alkaline phosphatase is a membrane enzyme on hepatocytes lining the biliary ductules.

<p>True (A)</p> Signup and view all the answers

Flashcards

Hepatic circulation routes

Blood reaches the liver through two pathways: the hepatic artery (oxygenated blood), and the hepatic portal vein (deoxygenated blood with absorbed compounds).

Hepatic artery

Carries oxygenated blood to the liver.

Hepatic portal vein

Carries deoxygenated blood to the liver, carrying absorbed nutrients & hormones.

Portal system

Blood circulation through two organs before returning to venous circulation.

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Liver lobules

Hexagonal structures that make up the liver. Each has a portal vein, artery, and bile duct branch.

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Sinusoids

Capillaries in the liver with large gaps, allowing for exchange between blood & hepatocytes.

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Hepatocytes

Liver cells responsible for metabolism (carbohydrates, lipids, & proteins) & storage.

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Carbohydrate metabolism

Liver's role in glucose storage as glycogen and creation of glucose from noncarbs.

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Gluconeogenesis

Liver creating glucose from non-carbohydrate sources.

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Lipid metabolism

Liver's role in fatty acid breakdown to create ketones (fasting) and lipoprotein synthesis.

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Ketosis

Liver breaks down fatty acids to produce ketones during fasting

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Lipoproteins

Liver produces these to package cholesterol and triglycerides.

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Protein Metabolism

Liver synthesizes proteins (albumin, globulins, fibrinogen) and clotting factors, converts amino acids.

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Bilirubin

A breakdown product of heme that the liver converts into a form excreted in bile.

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Kupffer cells

Phagocytes lining liver sinusoids, remove harmful substances

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Vitamin D metabolism

Liver metabolizes vitamin D produced from sunlight for use by the body

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Liver function tests

Used to assess liver health by measuring levels of proteins and enzymes.

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AST:ALT ratio

Indicates the type of liver damage.

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Albumin and prothrombin

Blood proteins produced by the liver, whose levels indicate liver function.

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Serum bilirubin

Indicates liver's excretory capacity; high levels indicate issues.

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Serum γ-glutamyltransferase (GGT)

Enzyme elevated in liver problems, including cholestasis.

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Alkaline phosphatase

Enzyme on liver cells, elevated with various liver issues.

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Cholestasis

Inability of the liver to excrete bilirubin, leading to accumulation in the blood.

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Study Notes

Hepatic Circulation

  • Blood circulates to the liver via two routes.

  • Oxygenated blood from the hepatic artery (branch of the cephalic trunk/arteries) supplies the liver.

  • Superior and inferior mesenteric arteries, and other branches, oxygenate the stomach, pancreas, small intestine, and large intestine.

  • Blood from these GI organs is collected and carried via the hepatic portal vein, containing absorbed nutrients and hormones.

  • A portal system involves blood passing through two organs before returning to venous circulation.

  • Blood is circulated through the liver sinusoids, a type of capillary with large gaps.

  • Blood is drained into the central vein of liver lobules, then into the hepatic vein, and finally the inferior vena cava.

Liver Lobules and Lobes

  • The liver is composed of lobes further divided into hexagonal lobules.
  • Each lobule corner is vascularized by a portal vein branch, hepatic artery branch, and a bile duct.
  • Oxygenated blood from the hepatic artery and deoxygenated (absorbed nutrient-rich) blood from the hepatic portal vein converge to form sinusoids.
  • Blood moves toward a centrally placed central vein.
  • Hepatocytes contact sinusoids and bile canaliculi.
  • Hepatocytes absorb compounds from the blood and detoxify others, also secreting bile into the bile canaliculi.
  • Kupffer cells (phagocytes) line the sinusoid walls and remove defective blood cells, bacteria, and other foreign materials.

Hepatocyte Functions

  • Metabolism:

    • Carbohydrate: Stores glucose as glycogen, breaks down glycogen into glucose, forms glucose from noncarbohydrates (gluconeogenesis), and makes triglycerides from glucose (lipogenesis) in the fed state.
    • Lipid: Metabolizes fatty acids to ketones in the fasting state; synthesizes lipoproteins for triglyceride and cholesterol transport; produces bile.
    • Protein: Synthesizes plasma proteins (albumin, globulins, fibrinogen), clotting factors; interconverts amino acids; converts ammonia to urea; recycles heme (bilirubin conversion).
    • Miscellaneous: Metabolizes Vitamin D; detoxifies compounds; contributes to hormone half-life.
  • Storage: Stores glycogen, fat-soluble vitamins (A, D, K).

Assessing Liver Function

  • Liver health is monitored by evaluating protein synthesis and excretory capacity.
  • Serum liver enzymes (AST, ALT) are indicative of liver damage.
  • AST:ALT ratios can distinguish various liver conditions or stages (e.g. non-alcoholic fatty liver disease, viral hepatitis).
  • Indicators of excretory capacity include serum bilirubin, y-glutamyltransferase (GGT), and alkaline phosphatase. Elevated levels can indicate conditions like cholestasis or liver diseases.

Review Questions: Bile Salt Pathway

  • Bile salts travel through hepatocytes, bile canaliculi, bile ducts, and finally the small intestine lumen to emulsify fats.

Review Questions: Blood Supply to Liver

  • Blood flows through the hepatic artery, sinusoids, central vein, hepatic vein, and vena cava to supply oxygen and remove CO2.

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