Lecture 9 - Overview of the Liver Flashcards
7 functions of liver? What 3 groups can they be made into?
METABOLIC:
1. Regulation of carbohydrate and protein metabolism
2. Beta-oxidation of fatty acids
SECRETORY/EXCRETORY:
3. Regulation of cholesterol excretion through bile
4. Bile production and secretion
VASCULAR:
5. Degradation of hormones and detoxification and excretion of drugs and toxins into bile
6. Vitamin storage
7. Synthesis of blood plasma proteins: albumin, globulins, clotting factors
Where does the hepatic vein drain? What is the pressure in it?
IVC
Around < 1 mmHg
What % of lymph does the liver produce? What % of lymph in thoracic duct is produced by liver?
50%
25-50%
What are the Kupffer cells of the liver? Role?
Big fixed phagocytotic cells (aka macrophages) that line the liver sinusoids
Roles:
- Cleanse the blood rapidly
- Take care of ~ 99 % of the bacteria entering the portal blood from the intestines
- Metabolize old red blood cells (NOT BILIRUBIN) once they have been eliminated in the spleen and some antigens
Describe the 4 roles of the liver with regards to carb metabolism. Overall?
1) conversion of galactose and fructose to glucose
2) gluconeogenesis
3) glycogen storage (used during fasting (~18 hr supply)
4) formation of chemical compounds from intermediates of carbohydrate metabolism
OVERALL: maintain blood glucose levels
Describe the 4 roles of the liver with regards to lipid metabolism. Overall?
1) has a high rate of beta-oxidation of FAs
2) forms most lipoproteins
3) synthesizes lots of cholesterol and phospholipids
4) converts unused carbohydrates and proteins to FAT!!!!
Overall: provides another energy source, provides the building blocks for membranes, intracellular structures, as well as steroid hormones, and can bulk up your fat stores
Describe the 4 roles of the liver with regards to protein metabolism.
1) deamination of amino acids
2) forms urea to remove ammonia from body fluid (excreted in urine)
3) forms 90% of the plasma proteins
4) interconversion among different AAs via transamination
What vitamins does the liver store?
A, D, B12
Liver role with coagulation?
Formation of blood coagulation products: fibrinogen, prothrombin, factor VII
Liver role with regards to iron?
Stores it in ferritin pools (Fe2+) as free iron is toxic
What are the bile acids formed from in the liver?
Cholesterol backbone
What are the 2 primary bile acids formed by the liver? Are these hydrophilic or hydrophobic?
- Cholic acid
- Chenodeoxycholic acid
Both hydrophobic
What are primary conjugated bile acids? Purpose?
Primary bile acids conjugated with taurine or glycine => makes them amphipathic (polar), which increases their water solubility to be able act on lipids by getting through the water layer
What are bile salts?
Bile acids with NaCl and HCO3- (which is almost always the case)
What are secondary bile salts? Where are these produced? Are these hydrophilic or hydrophobic or amphipathic? What does this mean?
Bile salts produced in the intestines when bacteria can dehydroxylate the primary bile salts and DECONJUGATE THEM:
- Deoxycholic bile salt
- Lithocholic bile salt
Mainly in the colon
Hydrophobic => harder to reabsorb them into enterocytes
What is bilirubin? What does build up cause? Describe the excretion pathway and whether the bilirubin is hydrophilic or hydrophobic.
Major end-product of hemoglobin degradation => carried to liver by albumin (HYDROPHOBIC) => uptook at sinusoidal membrane by organic anion transporters => transported/stored in liver => conjugated with 1 or 2 glucuronide (80%) or sulfate (10%) (HYDROPHILIC) => excreted into bile canaliculi by MRP2/ABCC2 and into the intestines as a “bile pigment” => bacterial deconjugation and degradation forms: urobilinogen reabsorbed into portal circulation (90%) (HYDROPHOBIC) WITH CONJUGATED BILE ACIDS (HYDROPHILIC) => portion of urobilinogen is converted to stercobilin (HYDROPHOBIC) and excreted in feces (10%) => a portion of urobilinogen (2%) is filtered at the kidneys and excreted into the urine, making the urine yellow, the rest (CONJUGATED AND NOT) is reabsorbed by the kidney
Build-up in the blood (eg, from obstructive liver disease) associated with jaundice
What can bilirubin levels be used for?
As diagnostic criterion for hemolytic blood diseases and liver disease
Normal pressures of liver capillaries and veins?
VERY low
What do we call the capillary net of the liver?
Sinusoids of the liver
What are liver cells called?
Hepatocytes
What is hepatic cirrhosis? What is it due to?
Chronic degenerative disease in which normal liver parenchyma is damaged and then replaced by scar tissue due to repeated toxic insults to liver (e.g. alcoholism, viral hepatitis) => obstruction of blood flow + decrease in functional hepatocytes
Where are lymphatics found in the liver?
EVERYWHERE
Role of production of lymph in liver?
Removes fluid and proteins from the Space of Disse to drain it into the venous blood
What is the Space of Disse in the liver?
Interstitial space between liver sinusoids and hepatocytes