Hepatobiliary System - Liver Flashcards
Which ligament separates the right and left lobe of the liver?
The falciform ligament
What structure anatomically separates the right and the left liver?
The middle hepatic vein
How any different segments does the liver have?
8
What is the purpose of the blood delivered to the liver by the hepatic portal vein?
carriers venous blood drained from the spleen, GI tract and associated organs
What is the purpose of the hepatic artery?
To carry blood from the aorta to the liver
Which two blood vessel compose of the dual blood supply of the liver?
- Hepatic artery
2. Portal Vein
What vessels are responsible for the outflor of the liver?
The hepatic veins and the bile ducts
How many hepatic veins are in the liver?
3 - Right middle and left hepatic veins
Which side of the liver are functional segments 1-4 found on?
The left side
Which side of the liver are functional segments 5-8 found on?
The right side
What is the teres ligament?
found emerging from the posterior side of the liver, reminants of the fetal umbilical cord
What is the sinusoid?
mixed arterial and venous blood which drain into the central veins
What are the two sides which all hepatocytes have?
They have a bile-canaliculi facing side and a sinusoid facing side
What is a hepatic lobule?
The hexagonal structual unit of liver tissue
What is found at each corner of a hepatocyte?
Portal triad
What is found at the center of each hepatic lobule?
central vein
What is the function of the central vein in the middle of the hepatic lobules?
collects blood from the hepatic sinusoids -> into the hepatic veins and into the systemic venous system
What is a portal triad?
Structure found at every corner of a hepatic lobule, consists of a hepatic artery, portal vein and a bile duct
What does the hepatic artery in the portal triad do?
Brings O2-rich blood into liver to support hepatocytes ↑ energy demands
What does the portal vein in the portal trial do?
bring Mixed venous blood from GIT (nutrients, bacteria & toxins) and spleen (waste products)
What do hepatocytes do with blood from the portal veins?
process nutrients, detoxify blood & excrete waste
What is the purpose of the bile duct in the portal triad?
Bile produced by hepatocytes drains into a bile canaliculi
What is a hepatic acinus?
Functional unit of the liver - consists of two adjacent 1/6th hepatic lobules, which share two portal triads and extend into the hepatic lobules as far as the central vein
Describe the three zone model ?
Zone 1 - closest to the edge of the hepatic lobules and near the portal triad
Zone 2 - middle
Zone 3 - closest to the central vein
Describe the blood which is recieved in zone 1?
Zone 1 is closest to the portal triad - therefore recieves the most oxygenated blood however has the highest risk of toxins
Describe the blood recieved in zone 3 of the hepatic acinus?
blood is low in oxygen, however also means the toxin risk is lower
Which zone of the hepatic acinus is usually affected by ischaemia?
Zone 1
What type of endothelial cells are sinusoidal endothelial cells?
Fenestrated - discontinuous endothelium
What do sinusoidal endothelial cells do?
Allow lipids & large molecule movement to and from hepatocytes
Where are Kuppfer cells found?
In the sinosoid, attached to the sinusoidal enodthelial cells
What are Kuppfer cells?
sinsoidal macrophages
What is the purpose of the Kuppfer cell?
Eliminate & detoxify substances arriving in liver from portal circulation via phagocytosis
Where are the hepatic stellate cells found?
In the space of disse
Where is the space of disse found?
In the gap between the hepatocytes and the sinosoid
What is the purpose of hepatic stellate cells?
Store Vitamin A in liver cytosolic droplets
What are the three roles of the hepatic stellate cells?
- Store Vitain A in the liver in cytosolic droplets
- Activated (fibroblasts) in response to liver damage
- Proliferate, chemotactic & deposit collagen in ECM
What hepatocytes responsible for synthesizing?
albumin, clotting factors and bile salts
What are cholangiocytes and what are there functions?
They are cells found lining the bile ducts, secrete bicarbonate and water into the bile
What are the metabolic and catabolic functions of the hepatocyte?
synthesis & utilization of carbohydrates, lipids and proteins.
What are the secretory and excretory functions of the hepatocyte?
synthesis &secretion of proteins, bile and waste products.
What are the Detoxification & immunological functions of the hepatocyte?
breakdown of ingested pathogens & processing of drugs
Describe how the liver participates in the cori cycle?
- Muscle cell takes up glucose - undergoes glycolysis
- This produces pyruvate
- One of the fates of pyruvate if lactate
- Lactate is taken up by liver and converted into pyruvate using lactate dehydrogenase
- Gluconeogenesis occurs in the liver, producing glucose from pyruvate
How many ATP molecules does gluconeogenesis require?
needs 4 ATP and 2 GTP
Describe the process of protein synthesis in the hepatocyte?
Amino acids are transported into the liver (in the fed state from the diet, in the fasting state from the muscle cells) where they are converted into secreted proteins like plasma proteins, clotting factors and lipoproteins which are then secreted out the liver
Describe how non-essential amino acids are produced?
Through different transamination reactions which involve different transaminase enzymes
When alpha-keto glutarate undergoes transamination, which amino acids are produced?
glutamate and proline
How is alanine (a non essential amino acid) produced?
through the transamination of pyruvate
How is aspartate produced?
Through the transamination of oxaloacetate
Muscle can potentially utilise amino acids to produce glucose for energy; but converting pyruvate to glucose requires energy. how is this problem overcome?
By transferring the problem to the liver -
- Pyruvate from glycolysis and glutamate from amino acid breakdown undergo deamination to produce ALANINE
- The alanine is transferred to the liver - here it undergoes another deamination reaction to produce GLUTAMATE AND PYRUVATE
- The glutamate is then converted into urea using 4 ATP which is then excreted
- The pyruvate is the converted into Glucose using 6ATP which is then taken up by the muscle cells
What is the main energy store in the body?
Fat
Where is fat stores?
In adipose tissue and the liver
What happens to excess glucose when glycogen stores in the liver are full?
When glycogen stores full, liver converts excess glucose & amino acids to fat for storage
Describe what happens to fatty acids in the liver?
fatty acids are converted into Acetyl CoA through beta oxidation which the enters into the TCA cycle
How is acetoacetate formed from 2 x Acetly CoA?
2 x Acetyl CoA makes aceto Acetly Coa
Adding another CoA makes HMG CoA
HMG CoA is then cleaved to form acetoacetate which is a ketone body and is used as a tissue energy source
Which two enzymes are involved in lipogenesis or fatty acid synthesis?
fatty acid synthase and Acetyl Co A Carboxylase
How are the hepatocytes involved in lipoprotein synthesis?
Glycerol and fatty acids combine to form tri-acyl glycerol in the liver
These tri-acyl glycerol molecules combine with apoproteins to make lipoproteins
What is one of the major roles for cholesterol in cells?
Maintenance of Cell membrane integrity
what is the purpose of LDL?
To transport cholesterol to tissues
What is the purpose of VLDL?
To transport fatty acids to tissues
What is the purpose of HDL?
They are empty - they are important fo picking up excess cholesterol
What is the hepatocyte responsible for storing?
Vitamin B12, A, D, E and K
Iron
Copper
What are the four fat soluble vitamins?
A, D, E and K
What process is vitamin K responsible for?
Blood clotting
How does the hepatocyte store iron?
As ferritin - ensures it is available for erythropoesis
Describe how the hepatocytes are involved in detoxification?
P450 enzymes:
Phase 1 (modification)
– more hydrophilic
Phase 2 (conjugation)
– attach water soluble side chain
to make less reactive
What are the uses of bile?
Cholesterol homeostasis
Absorption of lipids & lipid soluble vitamins (A, D, E, & K)
What is bile involved in the excretion of
Xenobiotics / drugs
cholesterol metabolites
adrenocortical and other steroid hormones
Alkaline phosphatase
How much bile
