Intro to Liver and Gallbladder Function Flashcards
What are the 6 main functions of the liver?
What is the function of the gallbladder?
What is meant by saying that the liver has a dual circulation occurring?
The GI system is […] resistance
Low
All blood that enters the GI tract and picks up nutrients from GI absorption drains into the […]
Portal vein
What happens to the flow of blood into the liver after a meal?
What is the first pass effect of the liver?
- Utilize nutrients –> liver carries out a lot of functions, so its very useful for it to have first dibs on nutrients
- Detoxify –> important to have any potential toxins entering body go first to a place where they could be detoxified before reaching heart and brain
- Modify drugs –> important to have drugs modified here so they can exert effects in systemic system without damage
Sinusoid = area where hepatic artery blood and portal vein blood mix before draining into central vein
Let’s consider a single layer of hepatocytes sandwiched between two sinusoids (see image). Describe the general possibilities for what enters these hepatocytes and what exits and how.
What is the role of liver endothelial cells?
Fenestrated border to allow flow of material from blood to space of disse
What is the role of liver stellate (ito) cells?
Vitamin A and lipid storage, release cytokines, involved in immune/inflammation/fibrosis
What is the role of liver Kupfer cells?
Macrophages (APCs) innate immune response, phagocytes for bacteria
What is the role of liver dendritic cells?
APCs
What is the role of liver Cholangiocytes (biliary endothelium)?
Secrete electrolytes into bile, regulated by secretin and Ach
- What is bile?
- Where is it made?
- What are its roles?
How does bile aid in lipid digestion?
What are the 4 steps in bile synthesis and circulation?
Describe the synthesis of cannilicular bile formation
Digestive contents from absorption in GI tract enter liver via portal vein –> mix with blood from hepatic artery via sinusoid –> hepatocytes absorb cholesterol –> modify it to make either cholic acid or chenodeoxycholic acid –> these are unconjugated bile acids that cannot cross canalicular membrane and they cannot be secreted as such –> hepatocytes conjugate to glycine or taurine to make conjugated bile acids which increases solubility and lowers pKa –> secreted actively into canaliculus
Describe what happens to canalicular bile after it is produced by hepatocytes.
1/ Active membrane pump action is required for canalicular bile secretion
2/ Secretin stimulates cholangiocytes to actively secrete fluid, bicarb and ions into bile. (Somatostatin inhibits it).
3/ This dilutes out the canalicular bile and ductal bile it drains into the biliary tree. Along its path it is modified by the epithelial cells (cholangiocytes) lining it.
4/ Bile then drains into the proximal small bowel, that is, duodenum, and is metabolized by enteric bacteria. Secondary bile acids are formed.
5/ Most bile is recycled via enterohepatic circulation, but some is lost with feces.
Once bile mixes with contents of duodenum, it continues through the GI tract. Much of it is reabsorbed by portal vein. Some of it makes its way to colon where it interacts with gut bacteria. What do the bacteria do to the bile?
They conjugate it again making it more hydrophilic. In order to prevent loss of this bile, the body has to deconjugate it in the colon to make it more lipophilic and thus able to be absorbed across intestinal wall into portal circulation.
What is enterohepatic circulation of bile?
Fatty acids arriving in duodenum triggers […] and this impacts gallbladder and pancreas by causing […]
CCK secretion into blood by intestinal I cells
Causes GB contraction, pancreatic enzyme release, relaxation sphincter of Oddi
Acidic chyme arriving in duodenum triggers […] and this impacts liver and pancreas by causing […]
Secretin secretion into blood by intestinal s cells
Liver duct cells secrete bicarb into bile, pancreatic ducts secrete bicarb into pancreatic enzyme secretions
What effect does vagus stimulation have on gallbladder?
weak contraction
Describe how RBCs are metabolized by the liver and how this leads to bilirubin in bile.
What is the role of ito cells in the pathogenesis of cirrhosis?
- Stellate cells normally store Vitamin A and lipids and make hepatocyte growth factors.
- Following chronic stresses (↑biliary pressure, fatty change, alcohol, viral or other inflammation) eventually stellate cells transform into myofibroblasts.
- Fibrosis is caused by these abnormally activated stellate cells making large quantities of collagen filling first the space of Disse, then the sinusoids.
