3 liver and gall bladder function

Question 1

describe the hepatic portal blood supply

Answer 1

• blood supply in series
• all organs’ drainage (deoxygenated) will be screen by liver before entering vena cava via hepatic vein

Question 2

describe the liver structure

Answer 2

organised into lobule that are delineated into vascular and bile channels

Question 3

how much biles does the liver produce a day

Answer 3

150-250mls

Question 4

what are secreted by hepatocytes? (consituents of bile)

Answer 4

• Bile salts: same as bile acids
  
  • Emulsification of fat droplets
• Phospholipids (lecithin)- maintain bile
• Bile pigment (bilirubin)
• Cholesterol (bile is major site of secretion)
• Inorganic ions- secrete bicarbonate ions, maintain fluid nature of bile

Question 5

What does bile salts undergo?

Answer 5

enterohepatic recycling

reabsorbed actively in ileum, reclaim 95%, goes to portal venous system then in liver the hepatocytes can reclaim bile salts

Question 6

what are bile pigments are major breakdown product of?

what does it combine with in the liver and why?

Answer 6

heamoglobin

glucuronic acid- increases polarity and solubility in water

Question 7

what happens to bile pigments when acted upon by bacteria?

what happens to the product

Answer 7

in the colon, produces urobilinogens

some taken up by blood, excreted in feces and kidneys (as urobilin- yellow)

some converted to stercobilin (brown pigment in feces)

Question 8

discuss inorganic secretion in bile

Answer 8

osmotic effect of bile acid secretion

Some reabsorption/further secretion by duct cells (dependent on rate of flow).

Question 9

what is the rate of bile production dependent on?

Answer 9

hepatocyte secretion

Question 10

what happens to bile during resting conditions (fasting)?

Answer 10

flow to duodenum prevented by sphincter of oddi

so enters gall bladder for storage

Question 11

what happens to bile in gall bladder

Answer 11

become concentrated due to reabsorption of salt and water in the gall bladder

Question 12

what happens to bile after a meal

Answer 12

neural influences and CCK- released in response to the presence of fat in duodenum

relaxes sphincter of Oddi and contracts gall bladder allowing bile to pass into duodenum

Question 13

how are gallstones produced

Answer 13

cholesterol crystallisation from bile salts

Question 14

discuss metabolism in the liver

Answer 14

1. fructose and galactose converted into glucose
2. glucose in liver taken up as glycogen, some coverted to TAG
3. fats combine with protein fraction and released as lipoproteins (VDL, HDL, LDL)
4. remainder glucose taken up by adipose tissue and muscle

Question 15

metabolism in the liver- what does it synthesise

Answer 15

albumin- plasma protein, clotting factors,

Question 16

important nutrients that the liver stores

Answer 16

vitamin ADEK (fat soluble), iron and copper

Question 17

why is liver a site of detoxofication and of what

Answer 17

Multiple enzyme system (cytochrome P450) allows modification of chemical structures, aim is generally to increase water solubility

• Endogenous* e.g. insulin, glucagon, aldosterone, female sex hormones
• Exogenous* e.g. drugs (some converted to active compound, some lost to first pass metabolism- must decrease dosage in LF due to decreased first pass metabolism)

Question 18

mechanisms involved in detoxification

Answer 18

Phase 1: oxidation/ reduction (increase reactivity)

phase 2: conjugation with

Amino acid, sulphate, glucuronic acid, acetic acid

(increase water solubility and excretion through kidneys)

methylation

Question 19

Jaundice

Answer 19

biluribin accumulation in plasma (>50 mM) – produces yellowing of skin, sclera and mucous membranes. May produce kernicterus – deposits of pigment in brain leading to nerve degeneration.

Question 20

causes of jaundice

Answer 20

1. haemolytic jaundice - excessive haemolysis of red blood cells (overwhelms liver capacity for excretion of biluribin). (Pre hepatic jaundice)
2. intrahepatic jaundice – defect in uptake or conjugation or secretion of biluribin by hepatic cells (common in acute hepatitis).
3. obstructive jaundice – blockage of bile ducts.
4. Physiological (not pathological) jaundice of the new born – babies have a poor capacity for conjugating biluribin.

ESP pre mature as liver immature

Question 21

types of hepatitis

Answer 21

Acute hepatitis: viral infections – hepatitis A, B, C

Drugs (e.g. paracetamol)

Chronic hepatitis (>6 months duration): viral infections – hepatitis B, C

Question 22

cirrhosis

Answer 22

Necrosis of liver cells – replaced by fibroblasts

caused by alcohol, hep B and C

no reversible treatment- stop cause, transplant and treat main cause