Liver Phsyiology And Function Flashcards
What are the main aspects of structure which influence function?
Vascular system
Biliary tree
3D arrangement of liver cells
Where does 75% of the blood supply to the liver come from?
Portal vein, returning from the GI tract.
Where does 25% of the blood supply of the over come from?
Hepatic artery = oxygenated blood
What is the role of the hepatic vein?
It takes blood back to the vena cava
What is the role of the portal vein?
It carries blood returning from the gastrointestinal tract. This blood is nutrient rich.
Where does blood travel to from the central vein?
This feeds into the hepatic vein, the blood flows back to the vena cava.
What does the portal triad consist of?
Portal vein
bile duct
hepatic artery
What are the two cell types in the liver (main)
Hepatocytes
Kupffer cells
What is the role of hepatocytes?
They perform most metabolic functions
What is the role of Kupffer cells?
A type of tissue macrophage
Explain the process of the biliary system:
Bile is secreted by hepatocytes
It travels through;
Channels between cells (canalinculi)
Ductules
Hepatic ducts
Common bile duct
Where is bile stored?
In the gallbladder
Where is bile made, secreted and stored?
Bile is secreted by the hepatocytes, then into the duodenum. It is stored in the gallbladder.
What is the function of bile?
Fat digestion and absorption
Elimination of waste products, specifically bilirubin and cholesterol.
How is bilirubin formed?
By the breakdown of haemoglobin. It’s toxic… yellowish pigment
What is cholecystokinin (CCK)
A peptide hormone of the GI system. This is responsible for stimulating absorption into the bloodstream.
It causes contraction of the gallbladder leading to ejection of bile into the duodenum.
What is enterohepatic circulation of bile?
Emulsifying fats and recycling bikes acids (and drugs).
Bile enters the duodenum via the common bile duct.
95% Reabsorbed back to the liver via the hepatic portal vein.
What is plasma protein synthesis?
Hepatocytes synthesis and release most plasma proteins.
Give 2 exams of 2 blood clotting factors.
Fibrinogen and prothrombin
What is the importance of vitamin K and where is it stored?
Stored in the liver, it is important for the formation of clotting factors
What form must vitamin K be in to allow clotting factors to be formed?
It must be in it’s reduced form.
How is oxidised vitamin K converted into its reduced form?
Enzyme epoxide reductase
What is the mechanism of warfarin?
It blocks activity of epoxide reductase.
So vitamin K stays in its oxidised form.
This means less clotting factors are being produced = anticoagulant effect
What is stored in the liver?
Carbohydrates, lipids
Fat soluble vitamins
Iron stored as ferritin
Give examples of fat soluble vitamins.
A, D, E, K and B12
What does the liver metabolise?
Carbohydrates
Lipids and proteins
What are the three sources of cholesterol?
Dietary
De-novo synthesis in liver
Cholesterol from extrahepatic tissue
How much cholesterol is made by the body in the liver?
50%
What are lipoproteins?
Combination of proteins and lipids.
Circulating around the body.
What are VLDLs?
This is how cholesterol leaves the liver. It transports fatty acids around the body.
What are HDL?
Circulates around the body, picks up excess cholesterol and takes it back to the liver.
What are LDLs
Transports cholesterol to tissues.
Bad cholesterol
What is the function of lipoprotein lipase enzymes?
They start breaking off triglycerides to use as an energy sourc.
What happens to excess cholesterol?
It’s excreted in bile.
Impaired blood clotting would likely result from damage to what key function of the liver?
synthesis of key proteins
Impaired blood clotting is likely to result from damage to the liver’s ability to produce key proteins. The liver produces key plasma proteins which are involved in clotting. Damage to the liver would prevent these from being formed
