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Physiology Exam 5 > 62 - GI Liver and Gallbladder > Flashcards

62 - GI Liver and Gallbladder Flashcards

1
Q

Describe the directional flow of blood and bile through the liver

A
  • Liver is divided into left and right lobes
  • Each lobe is divided into lobules
  • Lobules are arranged as stacks/plates of cells (primarily hepatocytes)
  • At the “corner” of each lobule there is a bile duct, hepatic artery and portal vein known as the “portal triad”
  • In the center of the lobule is the hepatic (central) vein
  • Blood flows from the hepatic artery and portal vein to the hepatic vein while bile flows away from the hepatic vein toward the bile duct
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2
Q

How does intestinal blood relate to this blood flow?

A

Intestines dump into portal vein which goes to the liver, out comes the hepatic vein that drains into vena cava – 70% of blood to the liver is from the portal vein. The liver is a FILTER for things that you take into your system

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3
Q

What is the role of hepatocytes?

A

Hepatocytes act as filters

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4
Q

What are the steps in biotransformation in the hepatocytes (think transformation of drugs that enter the body by the liver)

A
  • Uptake across basolateral membrane
  • Intracellular transport
  • Biotransformation (chemical modification and degradation)
  • Secretion across apical or basolateral membrane into blood or bile
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5
Q

How does uptake occur?

A

Uptake can occur via diffusion or protein transport

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6
Q

What are the two phases of biotransformation?

A

Phase I = molecular modification

Phase II = Conjugation

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7
Q

What is the overall goal of biotransformation?

A

To make molecules more water soluble

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8
Q

What does phase I accomplish?

A

Molecular modification

- This exposes a functional group via oxidation, reduction or hydrolysis

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9
Q

What does phase II accomplish?

A

Conjugation
- This is accomplished by using the exposed group from phase I in order to make the molecule more water soluble by glucoronidation, sulfation and acetylation

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10
Q

What is the bile salt biosynthetic pathway

A

From start to finish…

  • Cholesterol
  • Bile acid
  • Bile salt
  • Duodenum

The most common bile acid is CHOLIC ACID (know this)

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11
Q

What is the difference between primary and secondary bile acids?

A

Primary
- Primary bile acids are secreted by the liver

Secondary

  • Secondary are modified and secreted into the duodenum, go through the GI tract and are modified by intestinal flora
  • Secondary bile acids are the ones that bacteria change the chemical structure of
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12
Q

Where is bile stored and concentrated?

A

The gallbladder

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13
Q

How much bile is synthesized and secreted each day? What accounts for this?

A

Secretion
- 12-36 grams of bile salt secretion per day

Synthesized new
- Only 600 mg synthesized each day

Reasoning
The newly synthesized amount is the amount is lost in feces daily
- The rest is recycled after it goes through the GI tract
- The enterohepatic circulation is the recycling system
- 95% gets reabsorbed in the ileum

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14
Q

What is the key stimuli to promote the secretion of bile into the duodenum?

A

Primary simulus

  • CCK (cholicystokinin)
  • CCK induces gallbladder contraction and releases bile by relaxation of the sphincter of Oddi
  • This allows the ampulla to empty its cotents into the major duodenal papilla

Another stimulus

  • Acetylcholine
  • Not the main one, but plays a significant role
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15
Q

What is the key stimuli to inhibit the secretion of bile into the duodenum?

A

Primary inhibitor

- Somatostatin is the key negative regulator of gallbladder secretion of bile

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16
Q

What role does the enterohepatic circulation play in this process?

A

Reabsorbs 95% of bile from the GI tract for recycling and reuse

17
Q

Pathophysiology of jaundice

A
  • Jaundice is a condition of hepatocellular failure that is characterized by a yellowing of the skin due to elevated blood levels of bilirubin
  • Bilirubin is a product of heme metabolism following lysis of red blood cells in the liver
  • Impaired hepatic excretion of bilirubin causes an accumulation of bilirubin in the blood
18
Q

What does jaundice indicate?

A

Jaundice is therefore a clinical indicator of hepatic dysfunction

19
Q

What are the two types of jaundice?

A
  • Hemolytic

- Obstructive

20
Q

Describe hemolytic jaundice

A

Hemolytic jaundice (HJ) is simply caused by excessive breakdown of red blood cells

21
Q

Describe obstructive jaundice

A

Two types

  • Extrahepatic obstructive jaundice (EOJ) is caused by an obstruction, such as in the bile duct, which impedes bilirubin excretion outside the liver
  • Intrahepatic obstructive jaundice (IOJ) is caused by an obstruction in the liver, such as impaired hepatocyte function or blocked bile caniculi
22
Q

What is portal hypertension?

A
  • Portal hypertension is defined as high blood pressure in the portal venous system
23
Q

What causes portal hypertension?

A

The causes of portal hypertension are disorders that impede blood flow through the liver or vena cava

24
Q

What does long term portal hypertension lead to?

A

1 - varices: distension of collateral veins in the esophagus, rectum, and stomach.
2 - splenomegaly: enlarged spleen
3 - ascites: accumulation of fluid in the peritoneal cavity
4 - hepatic encephalopathy: accumulation of toxins resulting in cell death in the central nervous system

25
Q

What is cirrhosis of the liver?

A
  • Cirrhosis of the liver is characterized by fibrosis (scarring) of hepatic tissue resulting in altered hepatic blood flow and function.
  • The scarring of the hepatic tissue is a result of inflammatory process stemming from hepatitis (acute or chronic), alcoholism, biliary obstructions, or autoimmune conditions.
26
Q

What are the two types of cirrhosis?

A

Alcoholic cirrhosis and biliary cirrhosis

27
Q

Describe alcoholic cirrhosis

A
  • Alcoholic cirrhosis is caused by the accumulation of ethanol and the ethanol metabolite, acetaldehyde.
  • The high concentration of ethanol and acetaldehyde eventually disrupts hepatocyte function leading to cell death
28
Q

Describe biliary cirrhosis

A
  • Biliary cirrhosis is caused by an impediment of bile flow through blockage of the bile caniculi or bile duct.
  • Biliary cirrhosis can be caused by an autoimmune response which results in blockage of the bile duct.
  • Biliary cirrhosis can also develop from an obstruction caused by gallstones, tumors, strictures, pancreatitis, or cystic fibrosis
29
Q

Describe cholelithiasis

A

Cholelithiasis is the formation of gallstones in the gallbladder.

30
Q

What are the two types of stones that can form?

A

Cholesterol stones and pigmented stones

31
Q

Describe cholesterol stones

A
  • Cholesterol gallstones are precipitates of cholesterol that form from bile that is saturated with cholesterol.
  • This can occur from over production of cholesterol or impaired production of bile salts
32
Q

Describe pigmented stones

A
  • Pigmented stones are derived from calcium bilirubinate or other pigmented polymers.
  • The precipitation of these bile components frequently occurs as a result of a biliary obstruction
33
Q

Describe cholecystitis

A
  • Cholecystitis is an inflammation of the gallbladder.

- The inflammation can be caused by a stone becoming lodged in the cystic duct

34
Q

What is cholestasis

A

Impaired bile flow

Both cholelithiasis and cholecystitis may result in the general condition cholestasis

35
Q

On to Case #6

A

Go read case #6

36
Q

The case description is most consistent with what gastrointestinal pathophysiological condition?

A
  • Alcoholic cirrhosis
  • Portal hypertension
  • Hemorrhoids
  • Confusion
  • Tremor
  • Esophageal varices
37
Q

How does this condition contribute or cause the patient’s presentation and complaint?

A

Shunting or backing up of blood into the accessory organs of the GI tract

38
Q

Given the patient’s condition, what signs or symptoms may be exhibited?

A
  • You would also expect cirrhosis of the liver
  • Estrogen levels can rise in these patients, can lead to gynecomasty
  • Fluid in peritoneal cavity, distention will occur

Physiology Exam 5 (10 decks)

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