Lecture 10: Liver Physiology

Question 1

describe the blood flow between the liver and small intestine

Answer 1

• 9mmHg pressure difference
• low resistance for good blood flow
• 10% capacitance level

Question 2

describe how cirrhosis affects blood flow to and in the liver

Answer 2

causes the liver to harden which increases resistance thus decreasing blood flow

Question 3

name the metabolic functions of the liver

Answer 3

• carb metabolism
• fat metabolism
• protein metabolism
• detoxification
• tackling pathogens
• bile manufacture

Question 4

how does the liver function as a glucose buffer

Answer 4

• glycogen store
• decrease blood glucose after a meal (increased glucose uptake)
• increase blood glucose between meals or during prolonged starvation (glycolysis and glucose release)

Question 5

how does the liver function as a fat buffer

Answer 5

• right types of fats can be stored and released as and when needed
• fats stores can be used to make new glucose or make ketones + ATP

Question 6

describe the relation in flow between the hepatic portal vein and hepatic artery

Answer 6

inversely related

Question 7

which vessel in the portal area will experience more blood flow after a large meal

Answer 7

hepatic portal vein

Question 8

which vessel in the portal area will experience more blood flow after a period of fasting

Answer 8

hepatic artery

Question 9

what kind of pressure difference exists driving blood from artery to vein in the liver

Answer 9

small pressure difference therefore need low resistance to achieve big flow

Question 10

describe the liver’s function in protein metabolism

Answer 10

• liver is principal site of synthesis of all circulating proteins except y-globulins
• amino acids from intestine and muscles undergo transamination to then make up around 90% of plasma proteins
• some amino acids undergo deamination to from ammonia; liver detoxifies ammonia to form urea which can be excreted by kidneys

Question 11

describe the role of the liver in vitamin storage and activation

Answer 11

• liver stores vit A,D,E,K in fat stores (fat soluble vitamins)
• B12 also stored in liver (appx 80%)
• vit D activated in liver –> hydroxylated in liver then further hydroxylated in kidney

Question 12

describe the detox function of the liver

Answer 12

• Kupffer cells present on inner wall of sinusoids –> phagocytic and remove old RBC
• haemoglobin formed into bile
• alcohol, drugs, ALP, cholesterol detoxified for excretion
• fat soluble drugs detoxified –> water soluble then removed in bile or urine
• trace metals, steroid, ammonia detoxified

Question 13

describe the composition of bile

Answer 13

bile pigments and bile acids among other substances contained within an alkaline medium

Question 14

describe the function of bile

Answer 14

• excretion of Hb degradation by products (pigments)

- digestion of fats (bile acids aid formation of micelles)

Question 15

describe the metabolism and extraction of bilirubin

Answer 15

• globin part of Hb binds to bilirubin (bilirubin combines with albumin)
• this means bilirubin is not excreted in kidneys
• bound bilirubin absorbed into hepatocytes
• conjugated with glucuronic acid –> bilirubin diglucuronide (doesn’t cross into blood stream)
• then released into the bile
• broken down by bacteria in the intestine into urobilinogens
• urobilinogens can be reabsorbed into plasma (enterohepatic circulation)

Question 16

describe the cause of jaundice

Answer 16

excess bilirubin (free or conjugated) in the blood

Question 17

what symptom indicates a problem with bile excretion

Answer 17

dark urine –> excess conjugated bilirubin dissolves in water and can appear in kidneys

Question 18

name some symptoms of jaundice

Answer 18

• yellow skin
• yellow sclera
• yellow mucous membranes

Question 19

what causes prehepatic jaundice

Answer 19

excess production of bilirubin (haemolytic jaundice)

Question 20

what causes hepatic jaundice

Answer 20

decreased uptake of bilirubin, disturbed binding or insufficient transport of conjugated bilirubin into canaliculi

Question 21

what is posthepatic jaundice (cholestatic jaundice)

Answer 21

obstruction of the bile duct or gall bladder

Question 22

what is cholelithiasis

Answer 22

gallstones

Question 23

where do gallstones come from

Answer 23

cholesterol crystals OR calcium bilirubinate

Question 24

what causes newborn jaundice

Answer 24

newborn liver is very poorly formed so can take some weeks for metabolic processes to take place