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Flashcards in Liver - Anatomy Deck (28)
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How is the liver divided anatomically?


  • Anatomic- clinically insignificant but helps to facilitate segmental resection
    • four distinct lobes: 
      • Right and left with falciform ligament btw
      • Caudate and quadrate
  • Physiologic- 8 functionally independent segments known as the french (Couinaud) system
    • each segment has its own vascular flow and biliary drainage
    • reduces M&M if resections are done by segment
    • imaging done to create 3D modes for precision


Describe the microscopic anatomy of the liver lobule

  • Hexagonal shape on cross section
  • 6 vertically aligned portal canals at corners and central vein at center
  • Each portal canal contains:
    • connective tissue
    • lymphatics
    • nerves
    • portal triad
      • terminal branches portal vein
      • hepatic artery 
      • bile duct


How does the Acinus lobule concept differ from the classic lobule?

  • Small parenchymal mass arranged around a central axis consisting of: terminal hepatic arteriole, portal venule, bile ductule, lymp and nerves
  • blood enters the center of the acinus and flows out (centrifugally) to the hepatic venules
    • bile flows opposite direction


What are the different zones of the Acinus lobule concept?

  • Zone 1- Periportal zone
    • cells are closest to the portal axis, receive blood that is rich in oxygen and nutrients
      • major site of oxidative metabolism and conversion ammonia to urea
    • Most prone to reperfusion injury
  • Zone 2- midzonal region
    • the arbitrary intermediary transition zone
    • "anatomic reserve"
  • Zone 3- pericentral
    • cells at margin of acinus- receive blood that has exchanged gases and metabolites with cells in zones 1 & 2 
    • least resistant to metabolic and anoxic damage
      • most prone to ischemic damage
    • major site of CYP450 and anaerobic metabolism


How is the liver innervated?

  • Stimulation of SNS post-ganglionic T3-T11
    • increases hepatic vascular resistance (decreased blood volume)
    • increases glycogenolysis and gluconeogenesis (increased bs)
  • Stimulation of PSNS
    • increases glucose uptake and glycogen synthesis


How much of the CO goes to the liver?

How many ml/min to the portal vein? Pressure?

How many ml/min to the hepatic artery? Pressure?

What arteries feed the which organs that get picked up by the portal vein? (PIC)

  • High flow with low vascular resistance
  • CO = 25-27% = 1350 ml/min
  • Portal vein- 1050 ml/min
    • 75% blood flow, 50% O2 delivery
    • pressure = 9 mmHg
  • Hepatic artery- 300 ml/min
    • 25% blood flow, 50% O2 delivery


How is hepatic blood flow regulated?

  • Hepatic arterioles have a myogenic response to stretching that keeps local blood flow constant, despite changes in BP
    • An increase in transmural pressure (BP) causes vasoconstriction, preventing elevation in local bf
    • decrease causes dilation, preserving perfusion
  • Autoregulation of the hepatic artery is present in metabolically active liver (postprandial hyperosmolarity)
    • usually absen in the fasted state (most OR patients)
  • Volatile agents dose-dependently decrease this response
  • pressure-flow autoregulation does not exist in the portal circulation
  • **decreases in pH or O2 or increased CO2 increase hepatic artery flow.


What is the hepatic arterial buffer response?

  • Changes in portal venous flow induce reciprocal changes in hepatic arterial flow
  • As portal venous flow decreases, adenosine builds up in the piriportal region
    • increases in periportal adenosine cause decreased arteriolar resistance and hepatic arterial flow increases
  • Increases in portal venous flow washes out adenosine from the periportal region, raising arteriolar resistance and lowering hepatic arterial flow


What are some extrinsic influences on portal circulation?

  • Tone of pre-portal splanchnic organ arterioles regulate portal vein flow
  • decreases in pH or PaO2 (portal blood) often associated with increases in hepatic arterial flow
  • postprandial hyperosmolarity increases both the hepatic arterial and the portal venous flow.


What are the humoral influences on portal circulation?

Which one is a good treatment for portal hypertension and esophageal varicies?

  • Hepatic arterial bed has alpha 1, alpha 2, and beta 2 adrenergic receptors
    • Epi will cause vasoconstriction (alpha receptors) and vasodilation (beta receptor)
  • Portal vein has alpha receptors only
    • Epi injected into portal vein will cause only vasoconstriction (alpha)
  • Dopamine- weak vasoactive effects compared to Epi and NE
  • Glucagon
    • dose dep relaxation of hepatic arterial smooth muscle
    • antagonizes vasoconstrictor responses of the hepatic artery to various physiologic stimuli-including increases in SNS tone

  • Angiotensin II- 

    • severely constricts hepatic arterial & portal venous beds

    • markedly ↓ both mesenteric & portal venous flow; blood flow to liver may plummet

  • Vasopressin

    • intensely constricts the splanchnic arterial bed

    • lowers portal venous resistance….. effective treatment for portal hypertension/esophageal varacies


How is the liver involved with Lymph?

  • 50% of lymph is made in the liver
  • sinusoidal epithelium is extremely permeable, allowing fluid and proteins into the space of Disse
    • protein content in lymph is 6 g/dl (similar to plasma)
  • Slight increase in IVC pressure (10-15 mmHg) will increase lymph up to 20x
    • sweating from liver surface causes ascites


What are the alterations caused by cirrhosis?

  • Liver parenchymal cells are destroyed and replaced with fibrous tissue that impedes portal blood flow through liver
  • Secondary to alcoholism, poison ingestion (carbon tetrachloride), viral disease (hepatitis), bile duct obstruction and infection


_____% of liver can be regenerated in animal studies.


Normal liver function can occur after ____% has been resected.

70% of liver can be regenerated in animal studies.


Normal liver function can occur after 80% has been resected.


**liver disease impairs ability to regenerate


Why is the liver considered a blood reservoir?

  • Liver is an expandable organ
  • Hepatic arteries, veins, and capillaries contain 450 ml blood (10-15% TBV)
    • with R heart failure or increased R atrial pressure, liver can accomodate up to an extra L of blood.
  • Intense SNS response can significantly decrease blood flow and expell 400-500 ml within seconds
    • Anesthetics and liver disease impair this response


How does liver disease affect the endocrine system?

  • altered hormone levels and diminished hepatic synthesis of hormone binding globulins with altered metabolism and receptor regulation leads to significant endocrine abnormalities
  • Insulin-like growth factor 1 (somatomedin)- mediates actions of hormones from other endocrine glands
  • Angiotensinogen- precursor to Ang II, helps w/ fluid and electrolyte balance
  • Thrombopoeitin- stimulates bone marrow precursor cells to differentiate into plts
  • T4 conversion to T3 or inactivation
  • Inactivation of: 
    • corticosteroids
    • ADH
    • aldosterone
    • estrogen
    • androgens
    • insulin


What is the liver's immunologic function?

  • Kupffer cells make up 10% of hepatic mass, lining hepatic venous sinuses and clean blood of toxins, abcteria, etc
    • takes <0.01 second for the bacterium to pass into the wall of the kupffer cell after coming in contact with it
    • Kupffer cell can produce and recruit inflammatory mediators/neutrophils
  • Kupffer cells are impaired in advanced disease
    • contributes to sepsis/MODS


How does the liver metabolize carbohydrates?

  • Maintenance of normal blood glucose concentration
    • Storage of lg amts of glycogen (75 g or 24 hrs worth)
    • Conversion of galactose and fructose to glucose
    • gluconeogenesis (from aa and triglycerides)
    • formation of many chemical compounds from intermediate products of carbohydrate metabolism


How does the liver metabolize lipids?

  • Beta-oxidation of fatty acids to supply energy for body
  • Cholesterol, phospholipids and lipoprotein synthesis
  • synthesis of fat from proteins and carbohydrates


How does the liver metabolize protein?

  • Deamination of amino acids
  • formation of urea
    • removes ammonia from bodily fluids
  • plasma protein formation
  • amino accid synthesis and interconversions
  • can produce 12-50 mg protein/day


What kind of vitamins does the liver store?

How much?

  • Vitamin A- 10 months worth
  • vitamin D- 3-4 months worth
  • Vitamin B12- >1 yr worth
  • Iron as ferritin- "blood iron buffer"


Which coagulation factors does the liver produce?

Which ones require vitamin K?

  • All coagulation factors EXCEPT vWF, VIII, III & IV
  • Vitamin K dependent: **Bile required for Vit K absorption
    • Prothrombin/Factor II
    • factor VII
    • factor IX
    • factor X
    • Proteins C and S


The liver produces about ___% of hem.

What part of the metabolism of hgb is the liver responsible for?


Hepatocytes responsible for conjugating bilirubin and releasing it into bile and eliminated via alimentary tract


How much bile does the liver secrete?

  • Liver secretes 500 ml/day from common bile duct into duodenum
    • contains: conjugated bile salds, cholesterol, phospholipids, conjugated bilirubins, electrolytes
  • Bile acids help alkalinize and emulsify the large fat particles to increase surface area for digestion/aiding absorption
  • Bile is the means for excretion of waste products from blood (xenobiotics, bilirubin, Ca, and cholesterol)
  • Opioids (mu agonists) may interfere with biliary flow by increasing pressure in bile duct or causing SOOS
    • antagonized by VA, naloxone, nitroglycerine, atropine, and glucagon


What is the liver's role in pharmacokinetics?

  • Drugs bind to proteins synthesized by the liver which affects how the drug distributes (Vd)
  • Hepatic biotransformation = metabolism of drugs by hepatocytes changing them into inactive water-soluble substances that can be excreted and eliminated via the bile or urine
    • Phase I- hydrolysis, CYP450
    • Phase II- conjugation
  • CYP450- liver has more than 20 diff CYP enzymes
    • many oxidate drugs, environmental toxins, steroid hormones, lipids, and bile acids
    • Hepatocyte of zone 3 have the highest content of CYP proteins


What is the intrinsic clearance concept?

  • Intrinsic clearance reflects the fraction of the delivered drug load that is metabolized or extracted during a single pass through the liver
  • High clearance- clearance at or near rates they transverse the liver
    • lidocaine, benadryl, metoprolol
  • Low clearance- clearance independent of hepatic flow
    • diazepam, acetaminophen, warfarin
    • This is more significant when dealing with drugs that are highly protein bound


How is hepatocellular damage assessed?

  • AST- present with damaged liver cells, but can also be caused by other organs (heart, skeletal muscle, brain)
  • ALT- only produced by liver injury or necrosis
  • LDH-  Poor diagnostic specificity for liver disease
  • GST- found in multiple organs, sensitive indicator for liver damage
    • Best to get during a case
    • present in different tissues
    • iso-enzyme B is specific to liver
    • half life of 90 minutes- levels will quickly drop if there is no more hepatocyte damage


How is Bile flow assessed?

  • Alkaline phosphatase (AP) isoenzymes- generalized screening, idea about damage, but can be elevated with other normal situations
  • 5'-nucleotidase-  more specific info about if issue is extrahepatic or internal
  • Gamma glutamyl transferase (GGT)- not useful anymore
  • Serum bilirubin
    • conjugated- indicates obstruction
    • unconjugated- around surgery caused by hemolysis (lots of work to do)
      • issue with hepatocellular dysfunction
      • congenital problem


How can the liver's synthetic function be assessed?

good indicators of hepatic functions

  • Albumin (1/2 life 3 weeks)- half life too long to trend for acute situation
  • PT/INR (coag factor 1/2 lives 4 hours to 4 days)- better to trend for an acute situation