Liver and Gallbladder Part I Flashcards
The Functional Unit of the Liver is known as?
Lobule
Hepatocytes: What are they? Role in liver?
-the major parenchymal cells in the liver -play pivotal roles in metabolism, detoxification, and protein synthesis
Kupffer cells: What are they? Role in liver?
the resident macrophage in the liver • critical mediators of both liver injury and repair • can be protective • dysregulation can cause chronic inflammation in the liver
Dysregulation of Kupffer cells can cause ?
can cause chronic inflammation in the liver
Activation of stellate cells causes? This leads to ?
their activation in damaged liver causes secretion of collagen and formation of scar tissue → chronic fibrosis or cirrhosis
Describe the liver’s dual blood supply
• The portal vein providing 60% to 80% of hepatic blood flow • The hepatic artery supplying the remaining 20% to 40%
Describe the flow of blood from the aorta to the inferior vena cava?
In regards to liver microcirculation what “model” defines areas or zones?
acinar model
Describe the zones of the acinar model
- The center of the acinus (peri-portal) is zone 1: • main functions include gluconeogenesis, oxidation of fatty acids, amino acid catabolism, ureagenesis, cholesterol synthesis, and bile acid secretion
- The periphery (peri-venular) as zone 3: • particularly vulnerable to a circulatory failure • more involved with glycolysis and lipogenesis
- The region in between as zone 2
Why is zone 3 particularly vulnerable to circulatory failure?
It is the farthest away from the portal triad which means its farther away from oxygen and nutrients → makes it vulnerable to ischemia and circulatory issues
Hepatic oxygen delivery is related to the ?
oxygen content of blood going to the liver and total hepatic blood flow
What occurs to hepatic blood under systemic stress, such as sepsis?
• In sepsis: insufficient cardiac output cannot supply demands of the brain → hepatocellular hypoxia (in zone 3)
How does reperfusion injury occur in the liver?
• Mediated by generation of ROS once ischemic hepatocytes are re-exposed to oxygen → cell injury • Kupffer cells produce cytokines (inflammatory response)
Reperfusion of ischemic tissues is often associated with microvascular injury, particularly due to increased permeability of capillaries and arterioles that lead to an increase of diffusion and fluid filtration across the tissues. Activated endothelial cells produce more reactive oxygen species but less nitric oxide following reperfusion, and the imbalance results in a subsequent inflammatory response.[1] The inflammatory response is partially responsible for the damage of reperfusion injury.
There is an increased risk of ischemia is patients who have?
- Patients who have preexisting liver disease and portal hypertension are particularly susceptible since total hepatic blood flow may already be reduced. Splanchnic (aka splenic) blood that normally enters the liver may be shunted through collateral circulation, so bypassing the liver (and potentially resulting in varices). Also, decreased liver functions in patients with chronic liver disease makes them vulnerable to development of liver decompensation when there is added injury from an ischemic insult.
-Liver decompensations mainly are: ascites, variceal bleeding and hepatic encephalopathy
- Patients who have preexisting passive congestion of the liver are also at increased risk for ischemic injury. Increased central venous pressure (seen with heart failure) is transmitted to the hepatic veins and small hepatic venules that drain the hepatic acini. This increased pressure is associated with atrophy of hepatocytes in zone 3 of the liver acinus. The mechanism leading to atrophy is because of exudation of protein-rich fluid into the space of Disse due to the sinusoidal congestion. The resulting sinusoidal edema decreases the diffusion of oxygen and flow of nutrients to hepatocytes.
In addition to the atrophy of hepatocytes, chronic hepatic congestion can cause fibrosis, which fibrosis, in turn, decreases diffusion of nutrients to hepatocytes.
- Passive congestion by itself does not seem to be sufficient to cause significant hepatic necrosis without a related decrease in hepatic blood flow. Also, there is no clear correlation between the degree of congestion (as assessed by right atrial pressure) and zone 3 necrosis in patients with heart failure. Significant zone 3 necrosis caused by acute left-sided heart failure has been shown in the absence of right heart failure, suggesting that a decrease in cardiac output rather than congestion alone is the critical factor causing hepatic necrosis.
What are the major functions of the liver?
-Secretory -Excretory -Metabolic → metabolism of carbs, lipids, and proteins -Synthetic -Detoxification -Storage
What is glycogenesis ? When does it occur?
When excess glucose (after meals) is converted to glycogen
What is glycogenolysis? When does it occur?
Decreased glucose between meals stimulates breakdown of glycogen: glycogenolysis
What is gluconeogenesis? When does it occur?
• Exhaustion of glycogen reserves stimulates glucose production from amino acids and sugars: gluconeogenesis
What is gluconeogenesis? When does it occur?
• Exhaustion of glycogen reserves stimulates glucose production from amino acids and sugars: gluconeogenesis
Transamination leads to?
keto acids
Deamination leads to ?
ammonia
What is the process of protein metabolism?
Where does ammonia come from ?
bacterial degradation of amines, amino acids, purines, and urea in the gut
Describe the process of lipolysis ?
Fatty acid oxidation is the process where ?
triglycerides get broken down into glycerol and fatty acids (VLDL)
Phospholipid and cholesterol synethsis?
During phospholipid and cholesterol synthesis which also occurs in the liver, they are bound to lipoproteins and excreted through bile as cholesterol, then converted into bile acids
How does the formation of cofactors relate to the liver?
Liver requires vitamin K to manufacture prothrombin factors 7, 9, and 10
What is the etiology of abnormal hemostasis (arrest of bleeding) caused by abnormal liver function?
- abnormal coagulation factor synthesis
- synthesis of dysfunctional coagulation factors
- increased consumption of coagulation factors
- platelet disorders
What type of endogenous substances does the liver excrete?
- bilirubin
- steroid hormones
What type of exogenous substances does the liver excrete?
drug metabolites
What does enterohepatic circulation refer to?
Any substance secreted in bile which is reabsorbed from the intestine and returns to the liver to appear once again in bile may be said to undergo an enterohepatic circulation.
What are the vascular functions of the liver ?
-Acts as a reservoir of blood -Synthesizes about 50% of the circulating lymph
The liver secretes bile containing ?
the liver secretes bile containing:
- bilirubin,
- water
- bile acids
- electrolytes
- phospholipids and cholesterol
What is the purpose of bile acids?
digestion and absorption of fat and fat-soluble vitamins (D,A,K,E) from the small intestine