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59 Cards in this Set
- Front
- Back
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general fxns of liver
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1) filtration and storage of blood 2) metabolism of carbohydrates, proteins, fats, hormones, forgein chemicals 3) formation of bile 4) storage of vitamins and iron 5) formation of coagulation factors
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basic fxnal unit of liver
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lobule; constructed around central vein
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where do central veins empty
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hepatic veins then vena cava
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cellular plates
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arrangement of cells in lobule around central vein; like spokes of a wheel, generally 2 cells thick with bile caniculi between cell layers
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what lyes btwn cellular plates
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hepatic sinusoids filled with portal blood; hepatic arterioles
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spaces of disse/perisinusoidal spaces
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large pores in endothelial lining lead to these spaces located btwn endothelium and hepatic cells
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what do spaces of disse connect with
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lymphatic vessels and interlobular septa
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how much blood flow per minute through portal vein and hepatic artery?
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1050 mL and 300 mL; accounts for 27% of resting CO
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pressure difference from portal vein into liver to vena cava
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9 mmHg vs 0 mmHg
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why does pressure difference increase when parenchymal cells are destroyed
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replaced by fibrous tissue which contracts around blood vessels
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Why would someone die within a few hours of a block in the protal circulation
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portal hypertension causes large pressure increase in capillary pressure in intestinal wall; patient loses excessive fluids into lumens and walls of intestine
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normal blood volume of liver and potential blood volume of liver
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450 mL; can stor up to 1-1.5 L
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when would the liver expand to hold excess blood
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cardiac failure with peripheral conjestion
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under resting conditions how much lymph drainage is due to liver
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~1/2
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what occurs when hepatic vein pressure rises 3-7 mmHg above normal
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excessive fluids transude lymph and leak through outer surface of liver caspule into abdominal cavity
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What does fluid from liver leaking into abdominal cavity consist of?
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almost pure plasma with 80-90% normal protein content
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What occurs when venal caval pressures of 10-15 mmHg
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hepatic lymph flow increases up to 20 times normal; large free fluid build-up in abdomen
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control of rapid regeneration of liver
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hepatocyte growth factor (HGF)
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where is HGF produced
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mesenchymal cells in liver and other tissues (not by hepatocytes); only found in liver after operations
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what other signals may be important in liver regeneration
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epidermal growth factor, cytokines like TNF and interleukin-6
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inhibitor of liver cell proliferation
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transforming growth factor-B; cytokine secreted by hepatic cells
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how efficiently do Kupffer cells clean portal blood of bacteria
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less than 1% entering portal blood bacteria passes thorough into systemic circulation
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Fxns of liver in carbohydrate metabolism (4)
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1) storage of glycogen 2) conversion of galactose and fructose to glucose 3) gluconeogenesis 4) formation of many chemical compounds from intermediate products of carbohydrate metabolism
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specific fxns of liver in fat metabolism
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1) oxidation of fatty acids 2) synthesis of large quantites of cholesterol, phospholipids, and lipoproteins 3) synthesis of fat from proteins and carbohydrates
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deriving energy from neutral fats
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split into glycerol and fatty acids, fatty acids split by beta-oxidation , enter citric acid cycle to be oxidized
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what does beta-oxidation result in
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two-carbon acetyl radicals that from acetyl CoA
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What does liver do with excess Acetyl CoA it produces
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condenses two into acetoacetic acid
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How is acetoacetic acid transported
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highly soluble and passes from hepatic cells into extracellular fluid, enters circulation and is absorb by other tissues throughout body
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what percent of cholesterol synthesized in the liver is converted to bile salts
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80%; secreted into bile
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where does the remainder of cholesterol go
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transported by lipoproteins and carried by blood to cells throughout body
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What does liver do with fat it synthesizes
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transported in lipoproteins to adipose tissue to be stored
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Important fxns of liver in protein metabolism
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1) deamination of aas 2) formation of urea 3) plasma protein formation 4) interconversions of various aas and synthesis of other cmpds from aas
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why is deamination of aas required
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so they can be used for energy or converted into carbohydrates/fats
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where else can deamination occur
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some in kidneys, little in other tissues
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hepatic coma
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high ammonia concentration
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what percent of plasma proteins are produced in liver
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90%
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what else makes plasma proteins
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gamma globins, antibodies formed mainly by plama cells in lymph tissue
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rate of liver protein formation/day
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15-50 grams; can replace half of all proteins in about 1-2 weeks
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transamination
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available aa tranferred to keto acid and amino radical takes place of keto oxygen to form new aa
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vitamens stored in liver
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large amounts of Vit A (up to 10 months worth), D (3-4 months worth), and B12 (1-many years worth)
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apoferritin fxns
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blood iron buffer and iron storage medium
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coagulation substances formed by liver
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fibrinogen, prothrombin, accelerator globulin, factor VII, and other factors
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vit K is required to form what factors
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VII, IX, X, and prothrombin
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hormones altered by liver
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thyroxine, steroid hormones
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what does liver excrete into bile
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drug metabolites, Ca++, bilirubin
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reticuloendothelial system
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tissue macrophages
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Process of hemoglobin breakdown after RBC lysis
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split into heme and globin; heme ring is opened - iron binds transferrin and straight chain four pyrrole nuclei formed)
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What is produced from the straight chain four pyrrole nuclei formed
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biliverdin which is rapidly reduced to free bilirubin
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what happens once bilirubin enters liver
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about 80% is conjugated with glucuronic acid to form bilirubin sulfate; 10% conjugated with other substances; excreted into bile caniculi
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What happens to conjugated bilirubin in intestine
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converted by bacteria to urobilinogen (highly soluble); some reabsorbed
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what occurs to urobilinogen when exposed to air in urine
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oxidized to urobilin
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what occurs to urobilinogen when oxidized in feces
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becomes sterocobilin
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normal plasma concentration of bilirubin (mostly in free form)
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0.5 mg/dl
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when does skin become jaudiced
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bilirubin levels about 3 times normal
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common causes of jaundice
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1) increased RBC destruction-hemolytic jaundice 2) bile duct obstruction or damage to liver cells-obstructive jaundice
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what effects are seen in hemolytic jaundice
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increased plasma free bilirubin and increased urobilinogen absorption from intestines resulting in increased levels excreted into urine
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what effects are seen in obstructive jaundice
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conjugated bilirubin in plasma elevated due to rupture of caniculi and emptying into lymph; urine urobilirubin neg
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what test can be performed to differentiate btwn conj. And unconj. Bilirubin
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van den Bergh reaction
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kidney bilirubin secretion
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can excrete small amount of conjugated bilirubin, but not free albumin-bound
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