Liver and Gallbladder Function Flashcards
What is the blood supply in and out of the liver?
. Liver supplied by portal vein (70%, deoxygenated blood from stomach, pancreas, spleen, intestines) and hepatic artery (30%, oxygenated blood from coeliac trunk/aorta)
. Liver drained by hepatic veins (right, middle, left), which drain into IVC
Name 5 products of hepatocytes
Bile salts, bile pigment, cholesterol, phospholipids, inorganic ions
What is bile pigment?
. Breakdown product of haemoglobin in RBCs
. Excreted in bile
Give two important examples of bile pigment
Bilirubin (yellow) and biliverdin (oxidised form of bilirubin, green)
What colour is bilirubin?
Yellow
What colour is biliverdin?
Green
How is bile secreted and processed in the liver?
. Hepatocytes secrete primary secretion, which passes along duct cells
. Duct cells add bicarbonate ions to secretion to make it more alkaline
What is the purpose of enterohepatic recycling?
Means that bile salts don’t have to be continuously synthesised because they are uptake in the ileum with proteins and recycled to the liver via the portal vein
Describe how enterohepatic recycling works
. Liver secretes bile salts, which pass into gallbladder (stored here between meals), then into duodenum to emulsify lipids and aid digestion of fat
. Bile salts then move into intestines and into ileum, where proteins grab onto them
. The proteins with bile salts attached are absorbed in the ileum, and the bile salts are transported back to the liver via the portal vein to be re-used
What are bile salts derived from?
Cholesterol
True or false: Bile salt recycling (enterohepatic recycling) is 100% efficient
False, around 5% of the bile salts are lost during this process so this 5% needs to be synthesised to compensate
What is the lifespan of a RBC?
120 days
How is urobilin formed from urobilinogen?
Urobilinogen comes into contact with oxygen in the kidneys to become urobilin
How is urobilin eventually formed from the bile pigment bilirubin?
. Breakdown of Hb in RBCs produces bilirubin, which binds to albumin
. Bilirubin-albumin transported to liver, where the complex is broken down and bilirubin binds to glucuronic acid
. Glucuronic acid makes bilirubin more water soluble
. Bilirubin diglucuronide travels through intestines, where gut bacteria break the compound down to just bilirubin
. Hydrogen ions added in colon to form urobilinogen
. Some urobilinogen absorbed into portal system, passes through liver, then enters systemic blood (via hepatic veins, IVC etc.)
. Urobilinogen water soluble, so easy to filter in kidneys
. In kidneys, urobilinogen comes into contact with oxygen to become urobilin, which is then excreted in the urine
How does the gallbladder concentrate bile?
Takes in water and bicarbonate ions to make bile more concentrated
How do gallstones form?
Excess cholesterol or bilirubin in gallbladder (more than your bile can dissolve) forms little crystals, which can form bigger stones over time
How does the sphincter of Oddi control the movement of bile into the duodenum and gallbladder?
Sphincter of Oddi can open and close to allow bile into the ampulla of Vater in the duodenum (sphincter open) or into the gallbladder to be stored (sphincter closed)
Describe the role of CCK and neuronal signals in controlling the release of bile salts.
. Fat in duodenum stimulates neuronal signalling and release of CCK
. Sphincter of Oddi relaxes, gallbladder contracts
. Bile from gallbladder moves through sphincter into duodenum (ampulla of Vater) to work their magic and emulsify fat
What does the liver do with fructose and galactose?
Converts them to glucose
What does the liver do with fats and protein?
Converts them to lipoproteins (VLDL, HDL, LDL)
What does the liver do with glucose?
Converts it to glycogen or TAGs, or transported to adipose and muscle tissue
How come INR can be used to test for liver function?
The liver is a major site for clotting factors (and albumin), so if the liver isn’t working properly, there’ll be lower levels of clotting factors and the INR will be higher than normal
Which vitamins are fat-soluble? Where are these stored?
. A, D, E, K, iron, copper, some protein
. Stored in the liver
How is the liver involved in detoxification/excretion of compounds?
Make compound more reactive then add functional group to increase its solubility in water= more easily excreted
Give some signs and symptoms of jaundice
. Yellowed skin, sclera (white bit of eyeball), mucous membranes
. Kernicterus (deposits of pigment in brain –> nerve degeneration)
How can you treat jaundice?
Light- photo-oxidises bilirubin to break it down
Give 4 causes of jaundice
Haemolytic, intrahepatic, obstructive, physiological
What is haemolytic jaundice?
Excess haemolysis of RBCs= excess bilirubin, which can’t be processed by liver quickly enough
What is hepatocellular/intrahepatic jaundice?
Liver damage means that hepatocytes can’t conjugate bilirubin with glucuronic acid, so bilirubin can’t be excreted as easily (glucuronic acid normally makes bilirubin more water-soluble)
What is obstructive jaundice?
Bile duct becomes blocked (commonly by gallstones), which means that bilirubin builds up in the liver and a backlog occurs, spilling into the bloodstream
What is physiological jaundice?
Physiological jaundice of the new-born occurs when some new-borns can’t conjugate bilirubin
Why is urine yellow and stool brown?
. Colonic bacteria deconjugate and metabolise bilirubin into urobilinogen (colourless)
. Urobilinogen is oxidised to form urobilin (yellow) and stercobilin (brown)
. Urobilin excreted by kidneys= yellow urine
. Stercobilin excreted in faeces= brown colour
What is conjugated bilirubin?
Bilirubin conjugated with glucuronic acid (make bilirubin more water-soluble), catalysed by glucuronyltransferase
What is hepatitis?
Infection or inflammation of the liver (note: ‘it is= inflammation!)
What is acute hepatitis caused by?
. Viral infection (hep A, B, C)
. Drug overdose (e.g. paracetamol)
What is chronic hepatitis caused by? What timeframe is classed as chronic hepatitis?
. Viral infection (hep B or C)
. Over 6 months
What is cirrhosis?
Necrosis of liver cells, which are replaced by fibroblasts (scar tissue)
What is cirrhosis most commonly caused by?
Alcohol abuse or hepatitis B/C
What effect can cirrhosis have on blood pressure?
Can cause portal hypertension
What is a dangerous risk of portal hypertension?
. Blood can’t pass easily through portal system, so uses collateral system instead
. Some collateral vessels found in oesophagus –> oesophageal varices formed when high BP in these vessels
. When eating, food can push on these varices and cause them to pop, resulting in heavy oesophageal bleeding
. This can result in death
Is cirrhosis reversible?
No, only ‘cure’ is a liver transplant or minimising risks posed by secondary effects of cirrhosis
What is pruritus?
Severe itching of the skin (often due to liver damage)
