Hepatic Pathophysiology Flashcards
What is the largest organ in the body?
The liver
What is the functional unit of the liver?
The lobule about 50,000-100,000 in the liver
What cells are known as the macrophages of the liver?
Kupffer cells
What are the capillaries of the liver?
Sinusoids
What is the function of the space of disse?
Collects lymphatics fluid
From a radial view of a lobule, how might the provider determine the difference between the portal vein and hepatic artery?
The wall of the artery is thicker due to smooth muscle that is able to constrict the vessel
Where does blood come from to the hepatic artery?
Aorta and celiac circulation
Where does blood come from to the portal vein?
Brings blood from the intestines
Where does the bile drain to?
The intestines
Where does the liver receive O2 flow from?
Hepatic artery and portal vein (50:50 split)
What is the SaO2 of the portal vein?
85%
How much of the CO goes the liver?
1500mL or 25-30% of CO
What percentage of blood flow to the liver is from the portal vein?
1100mL or 75%
What percentage of blood flow to the liver is from the hepatic artery?
400mL or 25%
What is the average pressure in the hepatic vein leaving the liver and entering the IVC?
Averages 0mmHg
What is the average portal vein pressure entering the liver?
9mmHg
Why is it said that the hepatic sinusoids are a low pressure system?
Small pressure difference 9-0mmHg demonstrates that resistance to flow in the hepatic sinusoid is very low
About how long does it take for blood to traverse from the portal vein to the central vein?
8-9 seconds
What is hepatic arterial blood flow dependent on?
Metabolic demand (auto regulation)
What is hepatic portal vein blood flow dependent on?
Blood flow from the GI tract and the spleen
How will blood flow to the liver differ when change in one source occurs?
A change in blood flow from one source will produce a reciprocal (but somewhat limited) compensatory change in the blood flow from the other source
Decrease in hepatic arterial blood flow produces an increase in portal venous blood flow
What pathology greatly increases the resistance to blood flow in the liver?
Cirrhosis, destruction of liver parenchymal cells results in replacement wit fibrous tissue that contracts around the blood vessels
What is the most common cause of cirrhosis?
Alcoholism (viral hepatitis, obstruction/infection in bile duct and ingestion of poisons)
What is the most common cause of cirrhosis from poisoning?
Carbon tetrachloride, dry cleaning industry
What is the newest cause of cirrhosis that is on the rise?
Non alcoholic fatty liver disease found in the morbidly obese
What are the stages of alcohol induced liver damage?
Fatty liver –> liver fibrosis –> cirrhosis
What causes a fatty liver?
Fat deposition causes liver enlargement
What causes liver fibrosis?
Scar tissue forms, recovery is possible but scar tissue remains
What causes cirrhosis?
Growth of connective tissue destroys liver cells and the damage is irreversible
What type of receptors are located on the hepatic artery?
Alpha1 –> produce vasoconstriction and
Beta2 –> produce vasodilation
Dopamine1 –> produce vadosilation
Cholinergic –> vasodilation
What type of receptors are located on the portal vein?
Alpha1 –> produce vasoconstriction
Dopamine1 –> produce vasodilation
How does the SNS affect hepatic blood flow?
Sympathetic activation results in hepatic artery and mesenteric vessel vasoconstriction and decreased hepatic blood flow
What are the vascular function of the liver?
Functions as a blood reservoir
Hepatic macrophages serve as blood cleansing function
Liver has very high lymph flow
What is the normal amount of blood volume in the hepatic veins and sinusoids?
450mL
How much blood can potentially be stored in the hepatic veins and sinusoid as a result of back pressure from the RA?
0.5-1L of blood
How much blood can be shifted to central circulation from the liver when low pressure results such as during hemorrhage?
As much as 300mL
Why does blood entering the portal vein contain so much bacteria?
Because it comes from the intestinal capillaries
What bacteria is most commonly found in the blood of the portal vein?
Bacilli, however extremely rare to grow if you take a systemic sample of blood
What type of cells clean the blood entering the liver from the portal vein?
Kupffer cells that line the hepatic venous sinusoids, it takes about 0.01 second
What other function does the Kupffer cells do besides phagocytosis?
Release various enzymes, cytokines and other chemical mediators as part of an immune function
What system are Kupffer cells apart of?
Monocyte-Macrophage system (reticuloendothelial system)
Why does the liver have very high lymph flow?
Pores in the sinusoids are very permeable and allow easy passage of fluid and protein into the space of Disse
About how much of the lymph comes from the liver?
About 1/2 of all lymph in the bay comes from the liver
What can occur to the lymph fluid if high hepatic vascular pressure is present?
Causes fluid transudation into the abdominal cavity from portal sinusoids and the liver (ascites)
What hepatic vascular pressures result in excessive amounts of lymph fluid?
3-7mmHg increase above normal in hepatic venous pressure
What hepatic vascular pressure can increase lymph flow to 20x normal?
10-15mmHg increase in hepatic venous pressure, produces sweating from the liver surface with large amounts of free fluid entering the abdominal cavity
What causes ascites?
Blockage of the portal vein produces high pressure in the GI tract with transudation of fluid through the gut into the abdominal cavity
What are the final products of carbohydrate metabolism?
Glucose, Fructose and Galactose
What is the final common pathway of most carbohydrate metabolism?
Hepatic conversion of fructose and galactose to glucose
What are liver functions associated with carbohydrate metabolism?
Conversion of galactose and fructose to glucose
Storage of large amounts of glycogen
Gluconeofensis
Formation of many chemical compounds from intermediate products of CHO metabolism
What are glucose, fructose and galactose?
Simple sugars, all have the same chemical formula but their structural formulas are different
What is most of the glucose stored as?
Glycogen
What is the glucose buffer function?
Storage of glycogen allows the liver to remove excess glucose from the blood, store it and return it to the blood when BG concentration decreases
How does a diseased liver affect glycogen storage?
Glucose concentration can rise 2-3 times as much in a person with poor liver function compared to a person with normal liver function
What occurs when glucose storage capacity is exceeded?
The excess glucose is converted to fat
What are the only two things in the body that are able to store significant amounts of glycogen?
The liver and the muscle
What hormone enhances glycogen storage?
Insulin
What factors enhance glycogen breakdown?
Epinephrine and Glucagon (gucogenolysis)
When are glycogen stores depleted when fasting?
After 24hrs
What process is required when glycogen stores are depleted?
Gluconeogenesis, the generation of glucose from non-carbohydrate carbon substrates
What two organs are able to convert amino acids, glycerol, pyruvate and lactate to glucose?
The liver and kidneys
What agents increase gluconeogenesis?
Glucocorticoids, catecholamines, glucagon and thyroid hormone
What agent decreases gluconeogenesis?
Insulin
What cells are only able to use glucose for energy?
RBCs and renal medulla
What other source of energy can neurons use?
Ketone bodies produced in the liver by the breakdown of fatty acids following a few days of starvation
What are specific liver functions associated with fat metabolism?
Oxidation of fatty acids to supply energy for other body functions
Synthesis of large amounts of cholesterol, phospholipids and lipoproteins
Synthesis of fat from CHO and proteins
What is the purpose of oxidation of fatty acids?
To derive energy from Fat
How does oxidation of fatty acids produce usable energy?
They must split into glycerol and FAs
The FAs are then split by beta oxidation into 2-carbon acetyl radicals that form Acetyl Co A
Acetyl Co A enters the citric acid cycle
Where in the body does beta oxidation occur?
In all body cells but occurs especially rapidly in the hepatic cells
What happens to the Acetyl Co A that isn’t used by the liver?
Converted to acetoacetic acid, highly soluble and leaves the hepatocytes enters the blood and is absorbed by other tissues
What do the tissues do with the acetoacetic acid once absorbed?
Reconvert it back into Acetyl Co-A which enters the citric acid cycle
What is an additional function of Acetyl Co A in the liver?
Synthesize cholesterol and phospholipids
What is majority of the cholesterol in the liver synthesized into?
80% Converted to bile salts and secreted into the bile
Where does the remaining 20% of cholesterol in the liver go?
Packaged in lipoproteins and carried by the blood to all tissue cells in the body
What other component is synthesized in the liver and transported predominately as lipoproteins?
Phospholipids
What are the functions of cholesterol and phospholipids in the body?
Cell membrane
Intracellular structures
Chemical substances
What role does the liver play in fat metabolism?
Almost all synthesis of fat from CHO and proteins occurs in the liver
Without what function in the liver will death occur within a few days?
Protein metabolism
What are four specific liver functions associated with protein metabolism?
Deamination of proteins
Formation of urea for removal of ammonia from the body
Formation of plasma proteins
Synthesis of amino acids and synthesis of other compounds from amino acids
Why is deamination of proteins required?
Deamination of the amino acids in proteins is required before they can be used for energy or before they can be converted to CHO or fats
What is the byproduct of deamination?
Ammonia
Deamination of what amino acids plays a major role in gluconeogenesis?
Alanine
Where are branched chain AAs metabolized?
Metabolized by the skeletal muscle
What removed ammonia from the body fluids?
Formation of urea
What causes ammonia to form in the body?
Deamination process and bacteria in the gut with subsequent absorption into the blood
What can occur if the liver does not form urea?
Ammonia concentrations will rapidly rise and result in hepatic coma and death
What is a portal caval shunt and how does it affect ammonia levels in the blood?
Surgical procedure shunts blood from portal to arterial circulation, skips liver and increases amount of ammonia in blood –> encephalopathy
What are the only plasma proteins that are not formed by the hepatocytes?
Immunoglobulins
At what rate can the liver make plasma proteins?
15-50g/day
How does plasma depletion affect the liver?
Causes rapid mitosis of hepatocytes and liver growth
What are the most important quantitative plasma proteins?
Albumin (plasma oncotic pressure and binding for transport proteins)
What are the most important qualitative plasma proteins?
Coagulation factors
What is the difference between essential and non essential amino acids?
Essential have to be taken in dietary while non essential can be synthesized in the liver by interconversion of one AA to another
How are non essential AA formed?
Same chemical composition as the AA to be formed except at the keto oxygen
Amino radical is transferred from an available AA to the veto acid to take the place of the keto oxygen
What are the end products of drug metabolism?
Inactivated or are made more water soluble and can be excreted in urine or bile
What is included in the phase I reaction of biotransformation?
P450 enzymes and mixed function oxidases:
Oxidation
Reduction