Hepatic System (FINAL EXAM) Flashcards
Basic anatomy of the liver
The liver consists of a right and left lobe, separated by the falciform ligament
The right lobe has 2 additional lobes, the caudate and quadrate lobes
The liver is also described as having 8 different segments
The liver is composed of ___ lobules.
50,000 – 100,000 lobules
Each lobule in the liver consists of ___
Hepatocytes
Many portal tracts
Hepatic arterioles
Portal venules
Bile canaliculi
Lymphatics
Nerves
One Centrilobular vein
The acinus is ________
The functional unit of the liver
Includes same anatomical structures as the lobule, but the portal tract is in the middle and the centrilobular veins at the periphery
Consists of three zones
* Zone 1 is most sensitive to hepatoxic agents. Zone 3 is least sensitive to hepatotoxic agents.
* Zone 3 is most sensitive to ischemic injury. Zone 1 is the most protected in an ischemic event.
Kupffer cells
- Are macrophages found within the sinusoidal channels of the liver
- Essential to filtering bacteria, viruses, proteins and particulate from blood
What is bile?
A dark green fluid that aids in the digestion of lipids and absorption of vitamins A, D, E and K
Vitamin K deficiency is manifested as _____.
a coagulopathy due to impaired formation of prothrombin and of factors VII, IX, and X
Bile is produced by ____.
hepatocytes
Bile drains into the ____
the bile ducts and converges to form the common hepatic duct
The sphincter of Oddi controls the ____.
emptying of the common hepatic duct into the duodenum
Innervation of the liver
supplied by T6–T11 sympathetic nerve fibers, vagal nerve parasympathetic fibers, and right phrenic nerve fibers
Some autonomic fibers synapse first in the _______, whereas others reach the liver directly via ______.
celiac plexus
splanchnic nerves and vagal branches before forming the hepatic plexus
Sympathetic activation results in _____.
vasoconstriction of the hepatic artery and mesenteric vessels, decreasing hepatic blood flow
The liver receives what percent of cardiac output?
25%
Liver perfusion is supplied by which two vessels?
1) portal vein and 2) the hepatic artery
Details on the portal vein
supplies 70% of the liver blood flow and 50% of the oxygen
* Vasoconstriction: a1 receptors
* Vasodilation: D1 receptors
Receives venous blood that has passed through splanchnic circulation
blood flow dependent on spleen and GI tract flow
Details on the hepatic artery
supplies 30% of the liver blood flow and 50% of the oxygen content
* Vasoconstriction: a1 receptors
* Vasodilation: b2, D1, and cholinergic receptors
The hepatic artery is a branch from the aorta
* Blood flow dependent on autoregulation
Unique properties of blood flow with the hepatic artery and portal vein
Some **compensation **between portal vein and hepatic artery blood flow
Decrease in flow flow from one increases the flow the another
Where are the majority of our cytochrome p450 enzymes located?
Zone 3 of the Acinus
Intrinsic regulation revolves around ____
Intrinsic regulation = hepatic arterial buffer response
By adenosine
Limited by things like portal venous pressure
Extrinsic regulation revolves around ____
Extrinsic regulation = by metabolic state
↓ pH, pO2, ↑ pCO2 of portal blood→ ↑ hepatic artery flow to sustain metabolism
Hypercarbia can do what to hepatic perfusion
increase it
The liver is a reservoir for ___
blood
Low resistance of hepatic sinusoids allows ___
large blood flow through the portal vein
Small changes in hepatic venous pressure can result in ___.
large changes in hepatic blood volume
Chart comparing hepatic venous blood volume and hepatic venous pressure
What are some examples of how changes to hepatic venous pressure can influence blood volume?
- Intraoperative hemorrhage ➡️ decrease CVP ➡️ decrease hepatic venous pressure ➡️ shifts blood from liver to circulation (300 mL)
- Congestive heart failure ➡️ increase CVP ➡️ increase hepatic venous pressure ➡️ shifts blood from circulation to liver (1 L)
Function of Kupffer cells
Cleanse more than 99% of bacteria load
Process antigens
Release cytokines
The liver is the major organ for the storage of what?
Major organ for glycogen storage
What enhances glycogenesis?
Insulin
What enhances glycogenolysis?
Epinephrine and glucagon
The liver is responsible for the metabolism of ____.
macronutrients (like carbohydrates)
Glycogenesis = ____
Glycogenesis decreases the blood sugar level to normal.
Glycogenolysis = ____
Glycogenolysis increases the blood sugar level.
Glycogen stores are depleted after___.
24 hours of fasting
The liver and kidney can form glucose from ___.
lactate, pyruvate, amino acids and glycerol. Gluconeogenesis is vital for the maintenance of normal blood sugar.
Gluconeogenesis
Gluconeogenesis refers to synthesis of new glucose from noncarbohydrate precursors, provides glucose when dietary intake is insufficient or absent.
What enhances gluconeogenesis?
Glucocorticoids, catecholamines, glucagon and thyroid hormone
What inhibits gluconeogenesis?
Insulin
When carbohydrate stores are saturated, the liver converts the excess carbohydrates (and proteins) into _____.
fat (fatty acids), which can be used directly as fuel or stored in the liver or adipose tissue.
What can utilize only glucose?
Only RBCs and the renal medulla can utilize only glucose (even neurons can switch to fatty acid breakdown products – ketone bodies – after several days of starvation).
Discuss the liver and protein metabolism
The liver performs CRITICAL steps in protein metabolism. Without this function, death occurs in a matter of days.
* Deamination of amino acids (converts them to carbs and fats – “transamination”)
* Formation of Urea (formed from ammonia)
* Interconversions between nonessential amino acids
Discuss the liver and the formation of plasma proteins
Nearly all plasma proteins (except for immunoglobulins)
Albumin
ALL COAGULATION FACTORS (except for Factor III, IV and VIII
Anticoagulants: protein C and S, antithrombin III
Plasma Cholinesterase (pseudocholinesterase)
Drug Metabolism in the liver (general info)
Most drugs undergo hepatic biotransformation.
End products are inactivated or more soluble (more easily excreted in kidney or by bile)
There are two phases
Phase I of drug metabolism in liver
Phase I: via oxidases and P-450
Oxidation
Reduction
Deamination
Sulfoxidation
Dealkylation
Methylation
Phase II of drug metabolism in liver
conjugation
Enzymes systems, like the CYP450 system can be increased and decreased by ____.
exposure to other drugs
CYP450 inducers
Barbiturates, ketamine, benzodiazepines, phenytoin, chronic alcohol use, rifampin, glucocorticoids,
“Bad kids bring pot causing risky games”
CYP450 inhibitors
Acute alcohol use, Omeprazole, erythromycin, Cimetidine
“Always Offer Excellent Candy”
The liver converts ____
T4 to T3
