Gastrointestinal Module #2b Flashcards
What does the Glisson capsule do in the liver?
Sounds liver and contains blood vessels, nerves and lymphatics
What happens when the glisson capsule distends?
Causes pain
What is the functional unit of the liver?
Lobule
How are hepatocytes arranged?
Radially around central vein
Where are capillaries (sinusoids) located in the liver?
Between heaptocytes
From whom do sinusoids (capillaries) receive blood from?
Hepatic Artery
Hepatic Portal Vein
Where do sinusoids (capillaries) drain?
Central vein –> hepatic veins and IVC
Where are bile canaliculi located?
Plates of hepatocytes
Where do the bile canaliculi drain?
Small bile ducts –> eventually make their way into common bile duct
What are the immune/defense cells that line the sinusoids?
Kupffer Cells
Stellate Cells
Pit Cells
Disse Space
What are kupffer cells?
Macrophage (phagocytic) cells that line the sinusoids
What is the function of the kupffer cells?
Phagocytic cells –> RBC breakdown (bilirubin production)
What is clinically important about kupffer cells?
Early response to liver injury/pathology
Responsible for early steps in alcoholic (ethanol) induced injury
1st step in cascade of events leading to fibrosis/cirrhosis
What are stellate cells and where are they located?
Contractile cells
Located in perisinusoidal space
When do stellate cells become activated?
During pathology –> usually store vitamin A when dormant
What is the function of stellate cells when they become activated?
Contraction/relaxation to regulate sinusoidal blood flow
Production of scar tissue (collagen –> fibrosis) in development of cirrhosis
What do pit cells do?
Produce interferon and other immune defense substances
Clinically what is the function of pit cells?
“First line of defense” against tumor formation
Cytotoxic effect on tumor cells
What is the Disse space?
Interstitial space between hepatocytes and sinusoids that drains into lymphatic vesels
Describe the general pathway of bile (start w/ production)
Produced in Liver
Secreted into duodenum
Excreted/reabsorbed
What is the pH of bile?
7.6 - 8.6
What is bile alkaline?
Helps to neutralize stomach acids in duodenum
Describe bile
Alkaline, yellow fluid that is made mostly of water
What are the organic compounds found in bile?
Bile Salts
Cholesterol
Bilirubin
Phospholipids
What is the major organic compound found in bile?
Bile Salts
What are bile salts?
Conjugated bile acids
What does bile do?
Emulsifying agent to assist in breakdown of fats for absorption in small intestine and formation of micelles
What is bilirubin?
Yellow pigment from RBC (heme portion) degradation
Where is bile secreted into initially?
Canaliculi
Where do canaliculi eventually drain into?
R/L hepatic duct –> common hepatic duct
How much bile will flow into the gall bladder during fasting?
75%
What happens to the 25% of bile that doesn’t flow into the gall bladder during fasting?
Continue on and flow into the duodenum via common bile duct
What happens to the gall bladder during feeding?
Contracts and releases stored bile
What stimulates the gall bladder to contract during feeding?
CCK
Vagal stimuli
What is the name of the sphincter that allows bile to flow during feeding?
Sphincter of Oddi
What synthesizes primary bile acid?
Hepatocytes
What stimulates bile acid production?
CCK
Secretin
What is bile acid synthesized from?
Cholesterol
**major site of cholestserol metabolism
What are bile acids converted into?
Bile salts (they’re water soluble)
What do bile salts do in the duodenum?
Emulsify fat droplets –> physically arrange them into “micelles”
What are micelles?
Clumps (aggregates) of bile salts, fat droplets, fat soluble vitamins, cholesterol and phospholipids
Form circle w/ hydrophilic-ends on outside
What happens to bile in the ileum/colon?
90% = absorbed and transported back to liver
10% = continue to rectum and are excreted
Where are RBCs broken down?
Spleen
Liver = Kupffer Cells
Throughout Vascular System
How is hemoglobin divided during RBC break down?
Globin
Heme
What is globin further broken down into?
Amino Acids
What is heme further broken down into?
Iron –> stored in liver and recycled into new RBCs
Bilverdin –> further broken down into bilirubin –> released in plasma
What happens to bilirubin in blood plasma?
Attaches to albumin
In the blood plasma is bilirubin conjugated or unconjugated?
Unconjugated
What happens to the unconjugated bilirubin?
Circulates through hepatocytes in liver and is conjugated –> can be secreted into duodenum or stored in gallbladder
What happens to conjugated bilirubin in the duodenum?
Bacteria in intestines “deconjugate” it into urobilinogen
What are the 3 pathways that urobilinogen can follow?
Reabsorbed into blood stream –> excreted in urine or recycled in liver
Remain in coon and excreted in stool
What are normal values of urobilinogen in the urine?
0 - 4 mg/24 hrs
What kind of jaundice is increased values of urobilinogen in the urine considered?
Pre-hepatic jaundice
What is pre-hepatic jaundice caused by?
Hemolysis –> increased bilirubin production –> increased urobilinogen formation
What kind of jaundice is decreased values of urobilinogen in the urine considered?
Post-hepatic jaundice
What is post-hepatic jaundice caused by?
Obstruction –> blocks secretion of bile into intestine –> decreased urobilinogen formation
Less urobilinogen is reabsorbed into bloodstream for kidney to filter
What would your stools look like with post-hepatic jaundice?
Pale
What is jaundice (aka icterus)?
Bilirubin pigment causing yellow of skin (tissues) and conjunctival membranes
Is jaundice a specific disease/pathology?
NO its a symptom/sign of disease/pathology affecting metabolism/excretion of bilirubin
What are the 3 classifications of jaundice?
Pre-hepatic
Intra-hepatic
Post-hepatic
What does it mean for jaundice to be “pre-hepatic”?
Pathology PRIOR to liver –> increased RBC breakdown)
What are some diseases that would cause pre-hepatic jaundice?
Genetic diseases: Gilbert’s syndrome, sickle cell anemia, thalassemia
Kidney Disease
What does it mean for jaundice to be “intra-hepatic”?
Pathology located w/in the liver –> liver’s ability to conjugate bilirubin is impaired
What are some diseases that would cause intra-hepatic jaundice?
Cirrhosis
Hepatitis
Liver Toxicity
What does it mean for jaundice to be “post-hepatic”?
Pathology located AFTER liver –> impaired transport of conjugated bilirubin to GI tract
What are some diseases that would cause post-hepatic jaundice?
Gallstones
Pancreatic pathology that blocks to bile ducts
Can you use lab tests to DDx between classifications of jaundice?
Yes BUT need “whole picture” assessment of all LFTs, urine and stool analysis
**each jaundice classification has different lab patterns
What does serum bilirubin measure?
Both AMOUNT and TYPE of hyperbilirubinemia –> provide clues to jaundice classification
How is total bilirubin measured?
Directly in blood
**all 3 types of jaundice can have elevated total bilirubin
How is direct (conjugated) bilirubin measured?
Directly in blood
**elevated can indicate post or intra-hepatic pathology
How is indirect (unconjugated) bilirubin measured?
Calculated from total/direct measurements
**if elevated can indicate pre or intra-hepatic pathology
What serum enzymes can be measured when analyzing for jaundice?
Alkaline Phosphatase
AST
ALT
LDH
GGT
What serum proteins can be measured when analyzing for jaundice?
Albumin
Globulins
A/G ratio
transferrin
AFP = alpha fetoprotein
When looking @ urinalysis for jaundice what are you looking for?
Urobilinogen
Conjugated bilirubin
Color
What would you expect urine and stool to look like with pre-hepatic pathology of jaundice?
Urine = elevated urobilinogen
Urine color = normal
Stool color = normal
What would you expect blood tests to look like with pre-hepatic pathology of jaundice?
Blood: hyperbilirubinemia
Total bilirubin = elevated
Direct (conjugated) bilirubin = normal/potentially elevated (d/t increased production)
Indirect (unconjugated) bilirubin = elevated
What would you expect urine and stools to look like with post-hepatic pathology of jaundice?
Urine = dark –> elevated conjugated bilirubin and decreased urobilinogen
Stool color = pale –> d/t decrease of urobilinogen
What would you expect blood tests to look like with post-hepatic pathology of jaundice?
Blood = hyperbilirubinemia
Total bilirubin = elevated
Direct (conjugated) bilirubin = elevated –> d/t “congestive back up”
Indirect (unconjugated) = normal
What would you expect to see in intra-hepatic jaundice pathology?
Decreased uptake –> d/t CHF, drug/meds
OR
Decreased conjugation in the liver –> neonatal (pysiological), liver dz (hepatitis, cirrhosis), hyperthyroidism
What do you expect the labs to look like with intra-hepatic jaundice?
Elevated total bilirubin (d/t elevated conjugated bilirubin)
Elevated indirect (unconjugated) bilirubin (d/t congestive back up of indirect (unconjugated bilirubin in the blood stream)
Elevated direct (conjugated) bilirubin (d/t congestive hepatic “back-up”)
What will urine and stool samples look like in intra-hepatic jaundice?
Urine: increased conjugated bilirubin; normal or low urobilinogen
Urine Color = dark
Stool color = normal (no decrease of urobilinogen in stools
