Liver and Biliary System Diseases I Flashcards
Liver anatomy, histology, functions and assessment of function.
Where is the liver located?
In the upper part of the abdomen, where it occupies the right hypochondriac and the greater part of the epigastric region. [Upper right quadrant, right below the diaphragm]
The liver is divided into lobules by _________.
the line of insertion of the falciform ligament
The right lobe has on its posterior-inferior surface, two smaller lobes called the _____ and ________.
caudate and quadrate lobes
The liver is covered by ________.
the fibrous capsule of Glisson
The gallbladder is connected to the GIT via the ________ and _______.
cystic duct and common bile duct.
What is the function of the gallbladder?
To concentrate and store bile produced in the liver and release into the duodenum for the digestion of fats.
How is bile released?
By muscular contraction of the gallbladder, primarily in response to gut hormones, especially cholecystokinin (CCK), that are stimulated by digestive products in the GIT.
Describe the histology of the liver.
- Hepatocytes are arranged into hexagonal lobules, the functional units of the liver
- Each lobule has a hepatic venule (central vein) sitting in its centre and plates of hepatocytes separated by sinusoids into hepatic cords.
- At the edge of each lobule is a portal triad comprised of:
i. Hepatic artery: supplies 25% of blood supply as arterial blood
ii. Hepatic portal vein: supplies 75% of blood supply as deoxygenated nutrient-rich blood from GIT
iii. Bile duct and lymph ducts
What are the four types of cells that make up the liver?
- Hepatocytes
- Endothelial cells
- Kupffer cells
- Stellate/Ito cells
HEKS
What are the functions of the hepatocytes?
They make up 80% of liver parenchyma. They:
- store glycogen, vitamin B12, folic acid and iron
- aid the turn over and transportation of lipids
- synthesis some plasma proteins e.g. albumin, prothrombin alpha and beta globulins and fibrinogen
- secrete bile to metabolise fat
- help in steroid hormone turnover and regulate cholesterol
What is the function of the endothelial cells?
They line the sinusoids, which are capillaries that carry blood throughout the liver. Form fenestrations to control entry of plasma solutes and keep out RBCs
What is the function of the stellate cells?
- They contain fat droplets which store vitamin A.
- Differentiate in myofibroblast-like cells and synthesise extracellular matrix
- Involved in liver regeneration
What is the function of the kupffer cells?
- They are liver macrophages that adhere to lumen of sinusoids.
- Clear pathogens and act as APCs in adaptive immunity.
- Secrete cytokines and chemokines, which mediate inflammation.
What are the functions of zones I and III of the liver?
Zone I - oxidative processes such as:
-gluconeogenesis
-beta-oxidation of fatty acids
-cholesterol synthesis
-amino acid metabolism
-ureagenesis
- bile formation
Zone III- these processes don’t require oxygen
-glycolysis
-lipogenesis
-ketogenesis
-xenobiotic metabolism (detoxification)
-glutamine formation
What are the general functions of the liver?
- Carbohydrate metabolism:
- Protein metabolism:
- Lipid metabolism:
- Bile acid and Bilirubin metabolism:
- Drug and hormone metabolism
- Immunological function
Highlight the carbohydrate metabolism function of the liver.
The liver regulates glucose via:
- Glycogenesis: storing glucose as glycogen
- Glycogenolysis: breaking down glycogen into glucose
- Gluconeogenesis: creating glucose from non-carbohydrate sources
Highlight the protein metabolism function of the liver.
The liver regulates plasma protein levels.
- All circulating plasma protein except gamma-globulins are synthesised in the liver. - Synthesis of other proteins such clotting factors, complement proteins and acute phase proteins.
- Nitrogen excretion via amino acid transamination and oxidative deamination
Highlight the lipid metabolism function of the liver.
- Storage of fatty acids as triglyceride within very low-density lipoproteins (VLDL)
- Beta-oxidation of fatty acids for energy
- Production of lipoproteins which transport insoluble fatty acids
- Cholesterol formation, redistribution and excretion
Highlight the bile acid and bilirubin metabolism function of the liver.
- Synthesis of primary bile acids from cholesterol, which are then converted to secondary bile acids by GI microbiota
- Bile aids digestion of fats and provides alkaline pH for pancreatic ⁹ function
- Bilirubin, formed from RBC breakdown is conjugated with glucuronic acid in the liver and excreted within bile.
Highlight the Drug and hormone metabolism function of the liver.
- Most xenobiotics are inactivated in the liver by CYP450 enzymes, and excreted in bile or urine after conjugation by hepatic transferases
- The liver ins involved in the catabolism of hormones such as insulin , glucocorticoids, GH and PTH
- Angiotensin is produced in the liver
Highlight the immunological function of the liver.
- The liver helps filter the blood and remove debris, including bacteria and toxins
- Crucial site of gut-derived antigen presentation to Kupffer cells, NK cells and sinusoidal endothelium.
- The liver is involved in adaptive immunity via lymphocyte trafficking from the GIT.
Where is bile secreted?
At the hepatocyte canicular membrane via bile transporter proteins, with the contribution of biliary ductular epithelium.
Bile formation is stimulated by ______ and inhibited by _____.
Secretin and somatostatin
What is enterohepatic circulation?
It is the process by which substances from the liver (e.g. bile acids) are secreted into the bile, absorbed by the small intestine are returned to the liver through the portal vein.
