Liver (2)

Question 1

what 7 things make up the billiard system

Answer 1

1. Sinusoids
2. Central Veins
3. Bile duct
4. Portal vein
5. Hepatic artery
6. Bile canaliculi
7. Hepatocytes

Question 2

what is bile

Answer 2

Aids digestion of lipids in small intestine, excretes excess cholesterol and bilirubin.
Synthesised in the liver
Is stored in the gall bladder where it is released into the duodenum following eating

Question 3

what is bile composed of

Answer 3

• Water (85%)
• Bile Salts (10%)
• Pigments (3%)
• Fats (1%)
• Inorganic salts (0.7%)
• Cholesterol (0.3%)

Question 4

why is bile important

Answer 4

• Bile contains bile acids, which are critical for digestion and absorption of fats and fat- soluble vitamins in the small intestine.
• Many waste products, including bilirubin, are eliminated from the body by secretion into bile and elimination in faeces.

Question 5

why does bile excrete cholesterol

Answer 5

Cholesterol is a vital component of cell membranes and precursor of steroid hormones, vit D
Cholesterol is virtually insoluble in its free form
In Bile, however, it is made soluble by bile acids and lipids like lethicin (LCAT – lectin:cholesterol acetyltransferase )

Question 6

what are the 3 main functions of cholesterol

Answer 6

• It helps make the outer coating of cells.
• It makes up the bile acids that work to digest food in the intestine.
• It allows the body to make Vitamin D and hormones, like eostrogen in women and testosterone in men.

Question 7

describe The Enterohepatic Circulation

Answer 7

The Liver produces about 600mg bile acid per day but only a small amount is lost (~5%)
Most is reabsorbed into the blood in the duodenum
Venus blood from the ileum goes straight into the portal vein.
Bile acids extracted by hepatocytes and transported across the hepatocyte to be re-secreted into canaliculi

Question 8

________ secrete bile into _______, then into ___ ducts. This hepatic bile contains large quantities of ________, _______ and _________.
In the bile ducts bile is modified by addition of a watery, bicarbonate-rich secretion from ____ _______ cells.
The ____ ______ stores and concentrates (5xs) bile during the ______ state.

Answer 8

Hepatocytes secrete bile into canaliculi, then into bile ducts. This hepatic bile contains large quantities of bile acids, cholesterol and other organic molecules.
In the bile ducts bile is modified by addition of a watery, bicarbonate-rich secretion from ductal epithelial cells.
The gall bladder stores and concentrates (5xs) bile during the fasting state.

Question 9

what is the Role of Bile Acids in Fat Digestion and Absorption

Answer 9

Cholesterol from digestion or liver synthesis is broken down into bile acids (cholic/chenodeoxycholic acid)
Conjugated to an amino acid (glycine or taurine) – bile salts
Conjugated bile then enters the canaliculi –either enters duodenum or stored in gall bladder.

Question 10

what does Amphipathic nature of bile acids do

Answer 10

Amphipathic nature allows emulsification of lipid aggregates (act as detergents)
This increases the surface area of the fat and allows easier digestion by ligase
Allows solubility and transport of lipids (micelles form containing FA, cholesterol and monoglycerides

Question 11

what are other functions of bile

Answer 11

Bile serves as the route of excretion for bilirubin.
The alkaline bile has the function of neutralizing any excess stomach acid before it enters the ileum.
Bile salts also act as bactericides, destroying many of the microbes that may be present in the food.

Question 12

Liver Function Tests – what are they?

Answer 12

Measurement of blood components providing a ‘clue’ as to the existence and extent of liver damage
Composed of:
• traditional tests (bilirubin, aminotransferases and alkaline phosphatase)
• synthetic tests (albumin, prothrombin time and total
bilirubin)

Question 13

what do LFTs Assist in differentiating between

Answer 13

Obstruction to the biliary tract eg gall stones
– Acute hepatocellular damage - poisoning, infection, inadequate perfusion
– Chronic liver disease – alcoholic fatty liver, chronic active hepatitis, primary biliary cirrhosis

Question 14

describe Alanine aminotransferase (ALT)

Answer 14

• Found primarily in hepatocytes
• Released when cells are hurt or destroyed
• Normal levels depend on the reference range which actually differs lab to lab
• Considered normal between 5–40 U/L

Question 15

describe Aspartate aminotransferase (AST)

Answer 15

• Found in many sources, including liver, heart, muscle, intestine, pancreas
• Released on tissue damage
• Not very specific for liver disease
• Often follows ALT •Normal range: 8–56U/L

Question 16

describe Alkaline Phosphatase

Answer 16

• Found in liver (especially biliary tract), bones, intestines, & placenta (has to be used in conjunction with other tests eg GGT to check from liver)
• Synthesised by cells lining the bile canaliculi in response to cholestasis (intra or extrahepatic)
• Also raised in infiltrative diseases (i.e., stones or tumors) and cirrhosis
• Normal range: 20–70 U/L

Question 17

describe Gamma-glutamyl transpeptidase (gGT)

Answer 17

• Microsomal Enzyme found in lots of tissues including liver and renal tubules.
• Raised in cholestasis and sensitive index of liver pathology.
• Used in conjunction with ALP as doesn’t rise in bone disease (unlike ALP).
• Increased with high alcohol consumption and used to look at abstinence as stays in serum for 6 weeks.
• Normal levels 0 to 51IU/l

Question 18

describe bilirubin

Answer 18

• Indirect (unconjugated): old red cells, removed by the spleen, sent to the liver
• Direct (conjugated): Liver adds glucuronic acid, making these cells water soluble for excretion
• Normal range: less than 0.8mg/dL
• Total bilirubin: both direct and indirect types
• Excreted in the bile, down the common bile duct, into the small intestine
• Normalrange:0.3––1.0mg/dL

Question 19

describe albumin

Answer 19

• Liver is major site of synthesis – 1⁄2 life is 20 days so slow change if anything goes wrong
• Damaged liver can’t synthesise as much
• Hypoalbuminaemia leads to oedema. This is a feature of chronic liver disease (and very severe acute liver disease)
• Normal levels 3.2-4.5g/L

Question 20

describe Prothrombin

Answer 20

• Measures coagulation factors made by the liver – hepatic synthesis function
• 1⁄2 life ~ 60h – much shorter than albumin – preferred measure
• Can also be decreased in malnutrition , vit K deficiency therefore needs to be used in combination with other tests.