Liver and Gallbladder Function

Question 1

What is the blood supply in and out of the liver?

Answer 1

. 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

Question 2

Name 5 products of hepatocytes

Answer 2

Bile salts, bile pigment, cholesterol, phospholipids, inorganic ions

Question 3

What is bile pigment?

Answer 3

. Breakdown product of haemoglobin in RBCs

. Excreted in bile

Question 4

Give two important examples of bile pigment

Answer 4

Bilirubin (yellow) and biliverdin (oxidised form of bilirubin, green)

Question 5

What colour is bilirubin?

Answer 5

Yellow

Question 6

What colour is biliverdin?

Answer 6

Green

Question 7

How is bile secreted and processed in the liver?

Answer 7

. Hepatocytes secrete primary secretion, which passes along duct cells
. Duct cells add bicarbonate ions to secretion to make it more alkaline

Question 8

What is the purpose of enterohepatic recycling?

Answer 8

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

Question 9

Describe how enterohepatic recycling works

Answer 9

. 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

Question 10

What are bile salts derived from?

Answer 10

Cholesterol

Question 11

True or false: Bile salt recycling (enterohepatic recycling) is 100% efficient

Answer 11

False, around 5% of the bile salts are lost during this process so this 5% needs to be synthesised to compensate

Question 12

What is the lifespan of a RBC?

Answer 12

120 days

Question 13

How is urobilin formed from urobilinogen?

Answer 13

Urobilinogen comes into contact with oxygen in the kidneys to become urobilin

Question 14

How is urobilin eventually formed from the bile pigment bilirubin?

Answer 14

. 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

Question 15

How does the gallbladder concentrate bile?

Answer 15

Takes in water and bicarbonate ions to make bile more concentrated

Question 16

How do gallstones form?

Answer 16

Excess cholesterol or bilirubin in gallbladder (more than your bile can dissolve) forms little crystals, which can form bigger stones over time

Question 17

How does the sphincter of Oddi control the movement of bile into the duodenum and gallbladder?

Answer 17

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)

Question 18

Describe the role of CCK and neuronal signals in controlling the release of bile salts.

Answer 18

. 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

Question 19

What does the liver do with fructose and galactose?

Answer 19

Converts them to glucose

Question 20

What does the liver do with fats and protein?

Answer 20

Converts them to lipoproteins (VLDL, HDL, LDL)

Question 21

What does the liver do with glucose?

Answer 21

Converts it to glycogen or TAGs, or transported to adipose and muscle tissue

Question 22

How come INR can be used to test for liver function?

Answer 22

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

Question 23

Which vitamins are fat-soluble? Where are these stored?

Answer 23

. A, D, E, K, iron, copper, some protein

. Stored in the liver

Question 24

How is the liver involved in detoxification/excretion of compounds?

Answer 24

Make compound more reactive then add functional group to increase its solubility in water= more easily excreted

Question 25

Give some signs and symptoms of jaundice

Answer 25

. Yellowed skin, sclera (white bit of eyeball), mucous membranes
. Kernicterus (deposits of pigment in brain –> nerve degeneration)

Question 26

How can you treat jaundice?

Answer 26

Light- photo-oxidises bilirubin to break it down

Question 27

Give 4 causes of jaundice

Answer 27

Haemolytic, intrahepatic, obstructive, physiological

Question 28

What is haemolytic jaundice?

Answer 28

Excess haemolysis of RBCs= excess bilirubin, which can’t be processed by liver quickly enough

Question 29

What is hepatocellular/intrahepatic jaundice?

Answer 29

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)

Question 30

What is obstructive jaundice?

Answer 30

Bile duct becomes blocked (commonly by gallstones), which means that bilirubin builds up in the liver and a backlog occurs, spilling into the bloodstream

Question 31

What is physiological jaundice?

Answer 31

Physiological jaundice of the new-born occurs when some new-borns can’t conjugate bilirubin

Question 32

Why is urine yellow and stool brown?

Answer 32

. 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

Question 33

What is conjugated bilirubin?

Answer 33

Bilirubin conjugated with glucuronic acid (make bilirubin more water-soluble), catalysed by glucuronyltransferase

Question 34

What is hepatitis?

Answer 34

Infection or inflammation of the liver (note: ‘it is= inflammation!)

Question 35

What is acute hepatitis caused by?

Answer 35

. Viral infection (hep A, B, C)

. Drug overdose (e.g. paracetamol)

Question 36

What is chronic hepatitis caused by? What timeframe is classed as chronic hepatitis?

Answer 36

. Viral infection (hep B or C)

. Over 6 months

Question 37

What is cirrhosis?

Answer 37

Necrosis of liver cells, which are replaced by fibroblasts (scar tissue)

Question 38

What is cirrhosis most commonly caused by?

Answer 38

Alcohol abuse or hepatitis B/C

Question 39

What effect can cirrhosis have on blood pressure?

Answer 39

Can cause portal hypertension

Question 40

What is a dangerous risk of portal hypertension?

Answer 40

. 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

Question 41

Is cirrhosis reversible?

Answer 41

No, only ‘cure’ is a liver transplant or minimising risks posed by secondary effects of cirrhosis

Question 42

What is pruritus?

Answer 42

Severe itching of the skin (often due to liver damage)