3B Physiology of the Liver Flashcards
How much glycogen can liver cells store as a percentage of liver weight?
8% of liver cell weight 100-120g in adult
Where does aa degradation occur almost entirely?
Liver
What two enzymes are required for deamination in the liver?
AST and ALT, which are measure in blood to assess liver function
Where is essentially all urea synthesized in the blood?
Liver
What is a hepatic come or hepatic encephalopathy?
In serious liver disease, ammonia often accumulate in the blood
Where is urea excreted?
Kidneys
What is azotemia or uremia?
Toxic build up of urea in blood
What can cause an elevated BUN?
Impaired renal function, increased protein intake or catabolism, GI bleeding, dehydration
What is HMG-CoA-reductase?
important enzyme in liver hepatocytes required for endogenous cholesterol synthesis
What is the only way for the body to eliminate excess cholesterol?
Via bile
When does ketogenesis occur primarily?
Fasting states or poorly controlled type 1 diabetes
How does ketogenesis affect the pH of blood?
Lower pH (more acidic)
Does the liver degrade steroid hormones and T3 and T4?
Yes, sir!
What is hemachromatosis?
To much Fe+2 that begins to deposit in tissues
What does gastroferrin do?
Makes Fe+2 more soluble and transports it to the small intestine where it is released for absorption
What is transferrrin? Apoferritin? Ferritin?
Transferrin carries Fe+2 to liver. In liver apoferretin takes Fe+2 to make soluble and the Fe+2 and apoferretin complex is now called Ferritin. Ferritin is the stored form of Fe+2 in the liver
The liver stores large quantities of what vitamins?
A, B12, and D
What is the purpose of metabolizing drugs?
Make less active and more water soluble and thus readily excreted in urine and bile
Where are Cytochrome P450 enzymes most predominant?
Liver, intestines, lungs and other organs
What are conjugation reactions designed to do?
Make metabolites more polar or hydrophilic, sometimes after they have been created by P450 enzymes
What is the most common and most important conjugation reaction?
Glucuronidation
What is CP450 inhibition?
Decreased metabolic activity of CP450 enzymes leading to decreased metabolism of drugs
What is CP450 induction?
Increased metabolic activity of CP450 enzymes leading to increased metabolism of drugs
What stimulates Vitamin D activation in the liver?
PTH
What are the major types of plasma proteins?
Albumin, globulin, fibrinogen
Which plasma proteins are completely formed in the liver? Which one is 50-80% formed in the liver?
Albumin and fibrinogen. Globulin is 50-80% formed in the liver
Which blood clotting factors are synthesized in the liver?
All but III, IV and XIII
What is the composition of bile?
50% bile salts
40% phospholipids
4% cholesterol
2% bile pigments such as bilirubin
Does bile contain water?
Yes and electrolytes, these are secreted by cells lining the bile ducts
What are the two primary bile acids? Where are they synthesized?
Cholic acid and chenodeocycholic acid. Synthesized in the hepocytes
What converts a portion of the primary bile acids into secondary bile acids? What is the name of the secondary bile acids?
Intestinal bacteria does the conversion. Secondary bile acids are called deoxycholic acid and lithocholic acid
The liver conjugates bile acids with what two possible amino acids to form bile salts?
Glycine or taurine
What does the conjugation of bile acids w/ glycine or taurine do?
Makes the bile acids amphipathic at duodenal pH
What is the most common phospholipid found in bile?
Lecithin
Are phospholipids amphipathic?
Yes, sir!
The majority of cholesterol breakdown in the body is turned into what in the liver?
Bile
How much cholesterol is converted into bile acids and eliminated daily?
500 mg
What is the waste product of Hb degradation?
Bilirubin
What does conjugation of bilirubin involve? What enzyme is needed?
Attachmen of glucuronic acid to bilirubin.
Glucuronyl transferase
Which type of bilirubin is more water soluble?
Conjugated bilirubin
What cells secrete ions and water into the bile?
Ithelial cells lining the bile ducts
What are other waste products that go into the bile?
Lipolithic drugs and metabolites, antigen-antibody complexes
What are the three steps for formation of bile?
Secretion of bile into bile canals (canaliculi).
Intrahepatic ducts secrete water bicarb rich fluid.
B/w meals about 1/2 of hepatic bile is diverted to the gall bladder, which stores bile and removes salts and water
What volume to the first two steps of bile formation produce?
Around 900 mL/day or so called “hepatic bile”
What is the result of diverting bile to the gall bladder?
Gall bladder concentrates the key remaining solutes - bile salts, bilirubin, cholesterol and lecithin by 10-20 fold
During meals the bile that reachs the duodenum is relatively what?
Dilute hepatic bile and concentrated gall bladder bile
What are the two important functions of bile?
Provides sole excretion route for many solutes that are not excreted by the kidneys.
Secreted bile salts and lecithin are required for normal lipid digestion and absorption in small intestine
