Accessory Secretory Organs II Flashcards
what is the larger liver lobe
right lobe is larger than left
how is the liver divided for surgical purposes?
in 8 sections, each with a branch of the hepatic artery and portal vein
how much of the liver can be removed safely?
up to 70% if no fibrosis bc the remaining healthy tissue will take over function, and will grow back in as little as 30days
functions of the liver
- regulate metabolism 2. synthesizes proteins 3. stores vitamins 4. stores iron 5. inactivates and excretes drugs and toxins 6. major site of glycogen storage 7. glycogenesis 8. glycogenolysis 9. gluconeogenesis 10. LDL
how does the liver deal with fat chylomicrons
fat chylomicrons carried from SI by lymph are hydrolyzed by endothelial cell lipase (provides TAG and FAs for adipocytes) leaving cholesterol for degradation by hepatocytes to LDL
what direction does bile flow in a lobule
outward
what direction does blood flow in a lobule
inward toward the central hepatic venule
what makes up the hepatic triad?
bile duct, branch of the hepatic portal vein, and branch of the hepatic artery
what separates hepatocytes in sheets?
sinusoids which are cavities that enable the liver to hold large amounts of blood
what separates the sinusoids from hepatocytes
space of disse
whats the space of disse
separates the sinusoids from the hepatocytes. microvili from the hepatocytes extend into the space of disse to absorb nutrients from plasma in the space of disse, but RBC cannot enter. this is so direct exhange of metabolites can occur between blood and microvili of hepatocytes.
what is in the space of disse
mixed material from arterial blood, portal blood, and secretions from hepatocyte microvili
describe the liver sinusoidal blood vessel
has fenestrated endothelium to serve as a location for mixing of oxygen rich blood from the hepatic artery and the nutrient rich blood from the portal vein. separated from hepatocytes by space of disse
what blood empties into the sinusoids?
oxygen rich hepatic artery nutrient rich portal vein
why is bile excretion important?
is the only route of excretion of most heavy metals
what occurs in the sinusoids?
liver cells absorb nutrients and oxygen and filters out wastes and poisons.
what do the hepatocytes secrete into the sinusoids?
secrete sugars, vitamins, minerals, and other substances
how does blood leave the liver?
sinusoids drain into the central veins which join to form the hepatic vein, leaves through hepatic vein
what occurs if there is fatty acids in the duodenum?
CCK secretion increases and increases in concentration in the plasma. this causes gallbladder secretion increasing bile secretion into common bile duct. simultaneously the sphincter of oddi relaxes to allow bile flow into the duodenum
what does bile serve to do?
eliminate potentially harmful organic lipophilic substances including xenobiotics and toxins as well as endogenous substances like bilirubin and bile salts
what is the major route of excretion for cholesterol?
bile
what are bile salts necessary for?
major organic solute in bile and necessary for emulsification and digestive absorption of dietary lipids and fat soluble vitamins in the small intestine
what endogenous solid constituents are in bile?
95% water plus bile salts, phospholipids, cholesterol, amino acids, steroids, enzymes, porphyrins, vitamins, heavy metals
what is the fate of bile salts?
95% is reabsorbed in the small intestine to be recycled back to the liver – called the enterohepatic circulation 5% is lost in the feces
what is in the bile salts that is excreted in the feces?
waste products like bilirubin (RBC breakdown)
how much bile produced in the adult human?
400-800mL daily
what are the 2 stages of secretion of bile?
- initially, hepatocytes secrete bile into canaliculi from which it flows into bile ducts. 2. as bile flows through the bile ducts, modified by addition of watery, bicarb rich secretion from ductal epithelial cells
what does initial bile (when secreted from hepatocytes) contain
large quantities of bile acids, cholesterol and other organic molecules
how is bile modified?
by ductal epithelial cells, add watery-bicarb rich secretion
describe what happens to bile during fastin
bile is concentrated 5 fold in the gallbladder by absorption of water and small electrolytes – virtually all the organic molecules are retained
why do some newborns develop jaundice?
UDP glucuronyl transferase is synthesized slowly after birth, converts bilirubin to conjugated bilirubin to make bilirubin soluble.
describe RBC breakdown
RBC is broken down to hemoglobin. Hb–>biliverdin–>bilirubin (is insoluble)–binds to albumin in bloodstream–>bilirubin freed in liver–UDP glucuronyl transferase conjugates bilirubin to make soluble–>goes to bile–>in bile, conjugated–>urobilinogen enters enterohepatic circulation or made into urobilin and stercobilin and excreted in feces
how do hepatocytes metabolize cholesterol?
to cholic acid and chenodeoxycholic acid (primary bile salts)
what are the primary bile salts?
cholic acid and chenodeoxycholic acid, are lipid soluble only
how are the primary salts solubilized?
conjugated to taurine or glycine molecules to form water soluble conjugated bile acids. Na or K addition makes them bile salts
4 steps of enterohepatic circulation of bile salts
- liver hepatocytes synthesize and secrete bile components.
(bile salts 50%, cholesterol 4%, phospholipids 40%, bile pigments, ions, water)
- bile flows to gallbladder for concentration and storage
- CCK induced contraction ejects bile into duodenum to emulsify and solubilize lipids
- following lipid absorption, bile salts (which are deconjugated to secondary bile acids) are absorbed from the ileum into the portal circulation to the liver. hepatocytes extract bile salts.
what converts bile salts into secondary bile acids so they can be resorped into the circulatory system?
intestinal commensal bacteria
how often do bile salts circulate through the pathway?
10-12 times/day – liver to gut to liver, enterohepatic circulation
describe the path of bilirubin
some conjugated with glucuronic acid in the liver–>SI as bile–>colonic bacteria remove glucuronic acid–>urobilinogen–>reabsorbed into enterohepatic circulation OR oxidized to urobilin and stercobilin–>lost in stool
what makes feces brown
stercobilin and urobilin from urobilinogen
what is cholestasis
where bile cannot flow from liver to duodenum, could cause liver injury or possible death
2 types:
- obstructive
- metabolic
what is obstructive type cholestasis
mechanical blockage in the duct system that can occur from a gallstone, malignancy, or parasite migration (ascaris lumberoides, opisthorchis sineisis)
what is metabolic type cholestasis
disturbances in bile formation that can occur because of genetic defects, side effect of many meds, late pregnancy bc of hormones
what is characteristic of cholestasis
pruritis
jaundice
pale stool in obstructive cholestasis
dark urine
what causes jaundice
elevated bilirubin
what causes pruritis in cholestasis
bile acids act on opioidergic nerves
how do gallstones form
when bile contains either too much cholesterol or bilirubin or not enough bile salts. or when gallbladder doesn’t empty efficiently.
cholesterol in relation to gallstone
cholesterol secretion into bile is major elimination route. but free cholesterol is insoluble in aqueous solutions, but in bile is solubilized by bile salts and lipids (lethicin)
what makes up gallstones?
90% of gallstones are almost pure cholesterol or mixtures of choesterol and substances like mucin resulting from processes that allow cholesterol to precipitate from solution in bile
10% of gallstones are pigment stones that are composed of large quantities of bile pigmentts along with lesser amounts of cholesterol and calcium salts
what is the first symptom of liver disease?
pale stools
then
dark urine
bilirubin
swelling
excessive fatigue
bruising
what causes pale stools in liver disease?
bilirubin is yellow. is conjugagted with glucuronic acid in the liver (water soluble)–>enters bile–>colonic bacteria removes glucuronic acid which makes urobilinogen–>some reabsorbed some oxidized into urobilin and stercobilin–>feces = brown
absence of bilirubin produces whitish discoloration of feces
what causes dark urine in liver disease?
bilirubin mixes with urine due to impaired liver function or blocked biliary drainage
pruritis in liver damage
bilirubin deposits in the skin and act on opioidergic nerves
cannot be relieved by drugs
why does swelling occur in liver disease?
abdomen, ankles, feet because liver fails to make albumin and more water goes to ISF.
albumin also cannot carry unconjugated bilirubin so its insoluble)
what causes excessive fatigue in liver disease
generalized loss of nutrients, minerals, and vitamins
why does increased bruising occur in liver disease
bc liver makes clotting factors. if liver is damaged, no more clotting factors, more bleeding.
