GI Physiology 5 Flashcards by Alex Stein

Some key functions of the liver include

Nutrient metabolism
Synthesis of serum proteins
Storage of nutrients 
Immune function 
Detoxification/Biotransformation

How well did you know this?

Not at all

Perfectly

Biliary system consists of

Network of ducts that carry the hepatic secretory product (bile) to the intestine; and a bile storage site (the gallbladder)

How well did you know this?

Not at all

Perfectly

Biliary system is critical for

Assimilation of dietary lipids
Excretion of hydrophobic compounds
Neutralization of gastric acid

How well did you know this?

Not at all

Perfectly

Blood flow in the liver - The GI organs drain into the

portal vein

How well did you know this?

Not at all

Perfectly

Blood flow in the liver - what percentage of blood that flows to the liver comes from the portal vein?

75%

The remaining 25% is delivered by the hepatic artery

How well did you know this?

Not at all

Perfectly

Blood flow in the liver - from the liver, the blood drains from the ____ into ___

From the hepatic veins into the IVC

How well did you know this?

Not at all

Perfectly

Blood flow in the liver - the portal venous system delivers blood to the liver - thus….

Contents absorbed via the GI tract have to “pass through” the liver

How well did you know this?

Not at all

Perfectly

Portal hypertension

Inc in pressure in the portal venous system that occurs when there is dysfunction within the portal system
You will end up with pooling of blood in the GI organs

Thus - looking at GI organs can be indicator for liver dysfunction

How well did you know this?

Not at all

Perfectly

Lobules of the liver - Blood and bile flow in same/opp directions in the liver lobules

OPPOSITE

How well did you know this?

Not at all

Perfectly

Lobules of the liver - blood from the portal vein and hepatic artery empty into

Sinusoids - It flows toward the central vein

How well did you know this?

Not at all

Perfectly

Lobules of the liver - Bile will flow

Away from the central vein and towards the bile duct

How well did you know this?

Not at all

Perfectly

Describe the structure of the biliary system

Tree like

How well did you know this?

Not at all

Perfectly

Biliary tree - a small ductal system referred to as ____ empty into the ___ ____

Canaliculi empty into the bile ductule

The canaliculi interface directly with the hepatocyte

How well did you know this?

Not at all

Perfectly

Biliary tree The bile ductile then empties into

The bile or hepatic ducts that then drain into the common bile duct

How well did you know this?

Not at all

Perfectly

Cells of the liver

Hepatocytes
Kupffer
Endothelial
Stellate cells

How well did you know this?

Not at all

Perfectly

Cells of the liver - Hepatocytes

Functional cells of the liver
Polarized epithelial cells
Interface blood and bile

How well did you know this?

Not at all

Perfectly

Cells of the liver - Kupffer

Phagocytic macrophades
Exposed to portal blood
Host defense mechanism

How well did you know this?

Not at all

Perfectly

Cells of the liver - endothelial

Large pores between cells

Minimal basement membrane - they are not packed together tightly and have pores btw them

How well did you know this?

Not at all

Perfectly

Cells of the liver - Stellate

In the pores of the endothelial cells

The regulate the flow of blood (or bile) to the hepatocytes

Key steps in hepatocyte biotransformation

Uptake
Transport
Biotransformation
Secretion

Key steps in hepatocyte biotransformation - Uptake

Import of compound across the basolateral membrane

Key steps in hepatocyte biotransformation - Transport

Intracellular transport (they will bind to other transports and will be carried within the cell)

Key steps in hepatocyte biotransformation - Biotransformation

Chemical modification of degredation

Key steps in hepatocyte biotransformation - Secretion

Secrete products across apical or basolateral membrane
Put it back into the blood or put it into the bile

Water soluble - into blood
Less water soluble - into bile

Key steps in hepatocyte biotransformation - Biotransformation - phase 1

Chemical rxns like oxidation, reduction, hydrolysis -- You are taking the compound and adding a functional group to make them more water soluble/more polar

Key steps in hepatocyte biotransformation - Biotransformation - phase 2

Conjugation rxn We add a large/bulky group to the molecule to make it more water soluble Add things like Glucoronidation, Sulfation, Acetylation, Glycine Conjugation, Glutathione conjugatin

Key steps in hepatocyte biotransformation - goal of biotransformation

Take compounds and make them more water soluble

Bile acid synthesis - Bile acids and bile salts use what for synthesis

Biotransformation

Bile acid synthesis - One way is that primary bile acid (cholic acid) is first

Secreted into the bile Goes through to bile duct and then duodenum Primary is then converted to secondary and we inc diversity of our bile salts

Bile acid synthesis - Another way is that primary bile acid (cholic acid) can undergo

Biotransformation process (phase 1 and 2) and then we convert it to bile salt (which is more water soluble)

Bile acid synthesis - summary

From the liver, we get a mixture of bile acids and bile salts to be secreted into the duodenum Cholesterol is used to synthesize the bile acids and bile salts along with the biotransformation process

Enterohepatic circulation of bile acids and salts - liver will secrete bile - how many grams of bile acids and salts are in the bile that is secreted compared to how many bile acids/salts we make in a day

4-6 grams So liver makes 0.5 g of bile acid/salt a day - but 4-6 g is secreted in bile

Enterohepatic circulation allows for

Recycling of approx 90-95% of the bile acid/salt

Enterohepatic circulation - Ileum

Plays important role Ileum expresses a Na bile salt co transporter and is the primary site for update of bile acid/salt

Enterohepatic circulation - Two important things taken up by the small intestine

Bile acids/salts and Vit B12

Regulation of bile secretion

CCK stimulates gallbladder to contract and release bile CCK also causes relaxation of sphincter of oddi which allows passage opening of bile into intestine

Regulation of bile secreteion - key players

CCK and Ach Somatostatin will counteract both Ach and CCK

Liver function evaluation - Hepatocyte damage

Elevation of enzymes like alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the systemic circulation Elevated ALT and AST indicates hepatocyte damage (markers of cell death)

Liver function evaluation - Impaired protein synthesis

Dec in serum proteins in systemic circulation (albumin, clotting factors) Indirectly can measure clotting time

Liver function evaluation - Impaired biotransformation

You will get an increase in concentration of compounds that require conjugation for elimination - like estrogen, or bilirubin Can also get accumulations of toxins line ammonia

Liver function evaluation - Impaired bile flow (so blockage, liver is not damaged)

Inc concentration of conjugated bilirubin in the systemic circulation (leads to jaundice) Dec bile pigments in stool (leading to gray color of it) Dec bile secreted into the intestine (leading to fatty stool)

Hepatocytes and conjugation

We need hepatocytes to conjugate molecules

Liver function evaluation - do we have hepatocyte toxicity or do we have impaired bile flow

If there is conjugated bilirubin for example, that suggests that the liver function is good, but flow has decreased (so there is a blockage) If it were unconjugated - then we would think liver damage

Portal hypertension is a sign of what

Liver dysfunction | High blood pressure in the portal venous system

Consequences of portal hypoertension

Varices Splenomegaly Ascites Hepatic encephalopathy