The Liver

Question 1

What are the two major vessels that supply the liver

Answer 1

Hepatic artery and hepatic portal vein

Question 2

Describe the movement of blood in the liver

Answer 2

High blood flow and low vascular resistance

Question 3

What does the hepatic portal vein carry

Answer 3

Water soluble products of digestion absorbed from enterocytes into the villi capillaries

Question 4

What is the basic functional unit of the liver

Answer 4

The liver lobule

Question 5

Describe the structure of a lobule

Answer 5

Consists of hepatic cellular plates (2 cells thick) and has a central vein ( branch of hepatic vein carrying blood to vena cava) in centre, blood flows between hepatocytes from HPV via sinusoids (capillaries) and small bile canaliculi that empty in to bile ducts lie between adjacent cells

Question 6

What is a triad in a lobule

Answer 6

At the corner of each lobule a triad of 3 vessels exist as branches of the portal vein, hepatic artery and bile duct

Question 7

What are Kupffer cells

Answer 7

Macrophages within the liver

Question 8

What are the 3 main types of cells that the liver consists of

Answer 8

Hepatocytes, endothelial cells and kupffer cells

Question 9

What is the function of the liver

Answer 9

Energy metabolism and storage

Question 10

What 8 processes are controlled by the liver

Answer 10

Glycogenesis, gkycogenolysis, gluconeogenesis, lipogenesis, lipolysis, transanimation and deanimation and excretion

Question 11

Why must the liver maintain a store of glucose (glycogen store)

Answer 11

Glucose cannot be synthesised directly from fat stores in the liver

Question 12

How does circulating glucose enter liver cells

Answer 12

GLUT-2 glucose transporter

Question 13

How is glucose store in cells

Answer 13

As granules

Question 14

How are TAG carried in the blood

Answer 14

Hydrophobic so carried as lipoproteins (bound to protein albumin)

Question 15

What are drawbacks of glucose and protein storage

Answer 15

Carry large weight penalty

Question 16

What is the rate of glucose turnover

Answer 16

2mg/kg/min

Question 17

What is the rate of fatty acid turnover

Answer 17

1.7 mg/kg/min

Question 18

How much energy does glucose yield (kJ/g)

Answer 18

17

Question 19

How much energy does fatty acids yield (kJ/g)

Answer 19

38

Question 20

What % of total contribution to energy is from glucose

Answer 20

32%

Question 21

What % of total contribution to energy is from fatty acids

Answer 21

66%

Question 22

What hormones are released from the pancreas into the hepatic portal vein

Answer 22

Insulin and glucagon

Question 23

When is insulin released from the pancreas

Answer 23

When plasma glucose is above 5mmol/L

Question 24

What does the binding of insulin to the receptors on liver cell membranes stimulate

Answer 24

Glycogenesis, lipogenesis

Question 25

What is the function of glucagon

Answer 25

Elevate blood glucose when lower than 3 mmol/L by glycogenolysis in the liver

Question 26

What is the role of cortisol in liver function

Answer 26

Released from adrenal glands to stimulate liver gluconeogenesis so more blood glucose for brain

Question 27

What is the role of adrenaline (epinephrine) in liver function

Answer 27

Released form adrenal glands to stimulate glycogenolysis and lipolysis

Question 28

What are the 3 main ways glucose enters the blood stream

Answer 28

Absorption from small intestine (SGLUT1, GLUT2), glycogenolysis and gluconeogenesis in the liver

Question 29

What is gluconeogenesis

Answer 29

Synthesis of glucose from other precursors (amino acids, lactate and glycerol to maintain supply to brain

Question 30

What is lipolysis

Answer 30

Beta-oxidation of fatty acid

Question 31

What is de novo lipogenesis

Answer 31

Synthesis of endogenous TAG exported from liver into plasma as VLDL lipoproteins (adipose)

Question 32

How does the liver play a role in protein metabolism

Answer 32

First organ to receive dietary amino acids via hepatic portal vein and only organ capable of eliminating nitrogen from amino acids (deanimation/ eliminating amine group) to form ammonia and synthesis urea

Question 33

What hormone activates amino acid transporters to increase uptake

Answer 33

Glucagon

Question 34

What happens in the liver when we exercise

Answer 34

Increased glycogenolysis and gluconeogenesis Increased adipose tissue lipolysis and FFA mobilisation

Question 35

What happens to insulin and glucagon concentrations during exercise

Answer 35

Insulin falls so the glucagon to insulin ratio rises

Question 36

What is effect of an increased glucagon/insulin ratio during exercise

Answer 36

Adipose tissue releases fatty acid transporters (oxidation of fatty acids for local energy demands)

Question 37

What happens to protein during exercise

Answer 37

Increased protein breakdown from skeletal muscle or GI tract, so more AA is circulation as minor direct fuel for muscle (recycled in liver to make glucose)

Question 38

What happens to the associated nitrogen in broken down proteins when AA are recycled in the liver to make glucose during exercise

Answer 38

Converted and excreted as urea via kidney

Question 39

Why is liver metabolism not dominant during exercise

Answer 39

Reduced blood flow to liver

Question 40

What are the adaptations of the liver to exercise training

Answer 40

More effective at fat utilisation for fuel Reduces liver fat content

Question 41

How can the liver synthesis cholesterol (endogenous cholesterol)

Answer 41

From multiple molecules of acetyl-CoA

Question 42

What are bile salts composed of

Answer 42

Bile acids, phosphatidylcholine and cholesterol

Question 43

How are bile salts synthesised in the liver

Answer 43

Cholesterol is converted into cholic acid and chenodeoxyxholic acid (primary bile acids) in hepatocytes, primary bile acids ar conjugated to glycine or taurine

Question 44

Describe active reuptake of conjugated bile salts

Answer 44

In the terminal ileum via sodium dependent bile salt transporter into the portal vein to hepatocytes

Question 45

Describe lipoprotein synthesis

Answer 45

Remaining cholestrol synthesised in liver and phospholipids synthesised in the liver is incorporated into lipoproteins

Question 46

How are lipoproteins transported

Answer 46

Via blood to peripheral cells

Question 47

What are the functions of phospholipids

Answer 47

-lipoprotein synthesis and lipid transport in blood - membrane structure - thromboplastin synthesis - Sphingomyelin synthesis

Question 48

What are the other metabolic functions of the liver

Answer 48

Storage of vitamins A, D and B12 Storage of iron Synthesis of blood clotting proteins Detoxification Hormone excretion