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Human Physiology 2 - Unit 3 - Zach H. > Lecture 19: Physiology of Liver and Pancreas > Flashcards

Lecture 19: Physiology of Liver and Pancreas Flashcards

1
Q

Be familiar with each of the following.

Wasn’t a slide on these - refer to figure 70-1

A
  • central vein
  • hepatic veins
  • liver cell plates
  • bile canaliculi
  • sinusoids
  • space of Disse
  • portal vein
  • hepatic artery
  • lymphatic duct
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2
Q

What is the blood flow through the liver lobule?

A

Portal vein -> sinusoids -> central vein -> hepatic veins

Hepatic artery -> sinusoids -> central vein -> hepatic veins

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3
Q

Liver cell plates are composed of how many layers of hepatocytes?

A

Two layers of hepatocytes.

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4
Q

Liver cell plates are composed of two layers of hepatocytes. What is found between the two layers of hepatocytes in each cell plate?

A

bile canaliculi

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5
Q

What type of cells line sinusoids in the liver?

A
  • endothelial cells

- Kupffer cells (hepatic macrophages)

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6
Q

What space is found between endothelial cells and hepatocytes?

A

Space of Disse

part of the lymphatic system

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7
Q

Know figure 71-1 well for the exam!

A

Hepatic Lobule Figure

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8
Q

True or False:

The liver has high blood flow and high vascular resistance.

A

False - liver has high blood flow and low vascular resistance.

  • 1050 ml from portal vein + 300 ml from hepatic artery flows into sinusoids each minute.
  • 27% of resting cardiac output.
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9
Q

What is the portal pressure into the liver?

A

9 mm Hg

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10
Q

What is the pressure from the liver to vena cava?

A

0 mm Hg

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11
Q

What effect does cirrhosis have on blood flow?

A

Cirrhosis increases blood resistance to blood flow.

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12
Q

What is the effect of a clot blocking the portal vein or a major branch?

A

> Blockage of return blood from spleen and intestines.

> Increase in capillary pressure in intestinal wall –> loss of fluid –> death.

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13
Q

What is the normal volume of blood in the liver?

A

450 ml

(10% of body’s blood volume)

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14
Q

What happens to blood flow in the liver if there is high pressure in the right atrium?

A

High pressure in right atrium -> backpressure on liver -> increased blood volume in liver up to 1.5 L.

may occur during cardiac failure with peripheral congestion

Therefore: the liver can store blood in times of excess and supply blood in times of diminished volume

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15
Q

True or False:

Hepatic sinusoids are highly permeable to proteins.

A

True

efferent lymph has a protein concentration of 6 g/dl (almost equivalent to plasma concentration)

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16
Q

What happens if you have a higher than normal pressure in hepatic veins?

A

> Back pressure causes fluid to transude into lymph.

> Fluid leaks through liver capsule into abdominal cavity.

> Fluid is almost pure plasma.

> Large amount of fluid in abdominal cavity = ascites.

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17
Q

What are ascites?

A

Large amount of fluid in abdominal cavity.

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18
Q

What are the 7 major functions of the liver?

A
  • Carbohydrate metabolism
  • Fat metabolism
  • Protein metabolism
  • Vitamin storage
  • Immune function
  • Formation of coagulation factors
  • Removal or excretion of drugs, hormones, and other substances
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19
Q

List the specific happenings of carbohydrate metabolism in the liver.

A

> Stores glucose as glycogen.

> Converts galactose and fructose to glucose.

> Gluconeogenesis

> Forms many intermediate products of carbohydrate metabolism.

> Releases stored glucose into the circulation.

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20
Q

List the specific happenings of fat metabolism in the liver.

A

> Oxidation of fatty acids for energy.

> Synthesis of cholesterol, phospholipids, lipoproteins.

> Synthesis of fats from proteins and carbohydrates.

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21
Q

List the specific happenings of protein metabolism in the liver.

A

> Deamination of amino acids.

> Formation of urea.

> Formation of plasma proteins.

> Interconversion of various amino acids and synthesis of other compounds from amino acids.

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22
Q

Which vitamins are stored in the liver?

A

Vitamin A
Vitamin D
Vitamin B12

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23
Q

What coagulation factors are formed in the liver?

A

> fibrinogen
prothrombin
accelerator globulin
factors VII, IX, X

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24
Q

List the specific happenings in the removal or excretion of drugs, hormones, and other substances in the liver.

A

> Detoxifies or excretes into the bile:

  • sulfonamides
  • penicillin
  • ampicillin
  • erythromycin

potentially toxic substances are presented to the liver via the portal system. phase I reactions are catalyzed by P-450 enzymes. phase II reactions conjugate products from phase I reactions

> Excretes excess calcium into the bile.

> Detoxification and removal of ammonia and ethanol.

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25
Q

Hepatic bile is produced and secreted by what?

A

Liver

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26
Q

What is bile from the gallbladder?

A

Bile from the gallbladder is hepatic bile that has been stored and concentrated.

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27
Q

What are the components of bile?

A

> Bile Acids

  • cholic and chenodeoxycholic acids (synthesized by hepatocytes)
  • deoxycholic acid and lithocholic acid (converted by bacteria)

> Water and Electrolytes

> Cholesterol and Phospholipids (especially lecithin)

> Pigments and Organic Molecules (major pigment is bilirubin)

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28
Q

What is cholic and chenodeoxycholic acids synthesized by?

A

hepatocytes

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29
Q

What converts deoxycholic acid and lithocholic acid?

A

Bacteria

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30
Q

Bilirubin Formation

A

> Hemoglobin is released from damaged RBCs.

> Reticuloendothelial System

  • hemoglobin is phagocytized by macrophages
  • split into globin and heme
  • heme ring is opened to free iron
  • heme is transported in the blood by transferrin
  • straight chain of pyrrole nuclei is formed
  • heme is converted by heme oxygenase into biliverdin
  • biliverdin is converted to free (unconjugated bilirubin

> Free bilirubin is transported in the blood stream attached to plasma albumin to liver hepatocytes.

> Liver

-Free bilirubin is released from plasma albumin within the liver cells and conjugated.
*with glucoronic acid -> bilirubin glucuronids (80%)
(enzyme = UDP glucoronyl transferase)

  • with sulfate -> bilirubin sulfate (10%)
  • with a variety of other substances (10%)

> Conjugated bilirubin is:
- secreted (active transport) into the intestine OR excreted into the urine.

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31
Q

How is free bilirubin transported in the blood stream?

A

Attached to plasma albumin to liver hepatocytes.

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32
Q

What are the fates of conjugated bilirubin?

A

> secreted (active transport) into the intestine

> excreted into the urine

33
Q

Practice drawing out bilirubin formation cascade.

A

Slide 21 - bilirubin formation.

34
Q

What is Jaundice?

A

Refers to a yellowish tint to the body tissues.

35
Q

What is Jaundice usually caused by?

A

Quantities of bilirubin in the extracellular fluids:
> increased hemolysis
> obstruction of bile ducts or damage to liver

36
Q

What are increased hemolysis and obstruction of bile ducts or damage to the liver common causes of?

A

Jaundice

37
Q

What are the 3 major types of islet cells?

A

> Alpha
Beta
Delta

38
Q

What do alpha cells secrete?

A

glucagon

39
Q

What do beta cells secrete?

A

insulin and amylin

40
Q

What do delta cells secrete?

A

somatostatin

41
Q

What percentage of alpha cells make up the pancreatic islet?

A

25% of total cells

42
Q

What percentage of beta cells make up the pancreatic islet?

A

60% of total cells

43
Q

What percentage of delta cells make up the pancreatic islet?

A

15% of total cells

44
Q

What inhibits glucagon secretion?

A

Insulin - which is secreted by beta cells.

45
Q

What inhibits insulin secretion?

A

Amylin - which is secreted by beta cells.

46
Q

What inhibits insulin, glucagon, and gastrin secretion?

A

Somatostatin - which is secreted by delta cells.

47
Q

What does somatostatin do?

A

Inhibits insulin, glucagon, and gastrin secretion.

48
Q

What does insulin inhibit the secretion of?

A

glucagon

49
Q

What does amylin inhibit the secretion of?

A

insulin

50
Q

What islet cells communicate via gap junctions?

A

> beta cells to beta cells
alpha cells to alpha cells
beta cells to alpha cells

51
Q

What islet cells communicate via islet portal blood supply?

A

> beta cells to alpha and delta cells

52
Q

Via what does beta cells communicate to alpha and delta cells in the pancreatic islet?

A

Via islet portal blood supply.

53
Q

True or False:

Insulin circulates in unbound form in blood with half-life of 6 minutes.

A

True

54
Q

What happens to insulin not bound to receptors?

A

Destroyed in Liver

55
Q

What happens when insulin binds to its receptor?

A

> Increased uptake of glucose (decrease blood glucose)

> Increased permeability to amino acids, potassium, and phosphate ions (decrease blood amino acids and potassium)

> Increased uptake of fatty acids (decrease blood fatty acids)

> Increased activity levels for many enzymes.

> Changes in rates of translation and transcription.

56
Q

Review in the text - was not included in the lecture Powerpoint.

A

> Secretion process of insulin.

> Structure or insulin receptor.

57
Q

What is the structure of the insulin receptor?

A

Tetramer with two alpha (extracellular) and two beta (transmembrane) subunits.

intrinsic tyrosine kinase activity autophosphorylates the beta subunits, which then phosphorylate intracellular proteins

58
Q

True or False:

Insulin down-regulates its own receptors.

A

True

    • increased in starvation
    • decreased in obesity
59
Q

What is the effect of removing the pancreas on blood glucose, FFA, and acetoacetic acid levels?

A

> Blood Glucose - increases.

> Free fatty acids - sudden increase and then stays the same level.

> Acetoacetic acid - slowly starts to rise and then quickly increases by day 3 to 4.

60
Q

What is most of the glucose absorbed after a meal stored as?

A

Glycogen in the Liver

61
Q

What are glucose uptake mechanisms for the liver?

A

> Insulin inactivates liver phosphorylase.

> Insulin activates glucokinase and enhances uptake of glucose from blood.

> Insulin increases activities of enzymes needed for glycogenesis.

62
Q

What is one of the most important functional roles of insulin in the body?

A

Control from moment to moment whether fat (reduced insulin) or carbohydrate (increased insulin) will be used by cells for energy.

63
Q

List events that cause liver to release glucose into the blood.

A

> Decreased blood glucose resulting in decreased insulin secretion.

> Lack of insulin reverses glycogen synthesis pathway.

> Lack of insulin activates phosphorylase which splits glycogen into glucose phosphate.

> Glucose phosphatase removes phosphate from glucose and allows it to diffuse back into blood.

> Insulin inhibits gluconeogenesis.

64
Q

True or False:

Insulin promotes conversion of excess glucose into fatty acids and decreases utilization of fat.

A

True

65
Q

List the effects of insulin on fat storage.

A

> Increases transport of glucose into liver creating excess.

> Excess glucose is converted to acetyl-CoA

> Fatty acid synthesis is initiated.

> Newly synthesized fatty acids are converted into triglycerides and transported from liver as lipoproteins.

> Triglycerides are split into fatty acids in capillaries and taken up into fat cells.

> Insulin promotes uptake of glycerol by fat cells.

66
Q

What is the effect of the lack of insulin on fat storage?

A

> Large amounts of acetoacetic acids are formed in the liver.

> Carnitine transport mechanism in the liver is activated.

> Beta-oxidation results in excess of acetyl-CoA.

> Excess acetoacetic acids cause acidosis.

> Increase of ketone bodies in the blood.

67
Q

What are the two major effects of glucagon?

A

> Break down of liver glycogen.

> Increased gluconeogenesis.

Recall: released by alpha cells.

68
Q

What type of tissue does glucagon act on?

A
  • liver tissue

- adipose tissue

69
Q

List the glucagon cascade of events that lead to the increase in blood glucose.

A

> Activated adenyl cyclase in hepatic cell membrane.

> Which cuases formation of cAMP.

> Which activates protein kinase.

> Which activates phosphorylase B kinase.

> Which converts phosphorylase B into phosphorylase A.

> Which promotes degradation of glycogen to glucose-1-phosphate.

70
Q

Besides causing the break down of liver glycogen and increased gluconeogenesis, what else does glucagon increase?

A

> Increases lipolysis

> Increases urea production (due to deamination of amino acids used for gluconeogenesis)

71
Q

What is the major factor that regulates glucagon secretion?

A

blood glucose concentration

72
Q

What does increased blood amino acids stimulate?

A

glucagon secretion

73
Q

Increased blood amino acids stimulate glucagon secretion. What does this prevent?

A

Prevents hypoglycemia due to unopposed insulin in response to a high protein meal.

74
Q

What cell type secretes somatostatin?

A

delta cells

75
Q

What major effects does somatostatin cause?

A

> inhibits secretion of insulin, glucagon, and gastrin

> decreases motility of stomach, duodenum, and gallbladder

> decreases secretion and absorption of GI tract

76
Q

List negative effects of having an increased blood glucose level.

A

> increased osmotic pressure in extracellular fluid

> loss of glucose in urine

> osmotic diuresis (dehydration and loss of electrolyts)

> damage to tissues and blood vessels

77
Q

Diabetes Mellitus Type I (IDDM)

A

> Due to lack of insulin secretion.

> Injury to Beta cells:

  • viral infections
  • autoimmune disorders
78
Q

Diabetes Mellitus Type II (NIDDM)

A

> Due to insulin resistance.

> Obesity is major risk factor.

> Preceded by metabolic syndrome.

79
Q

List the conditions that a patient with metabolic syndrome would present with.

A 
> obesity (esp. abdominal fat)
> insulin resistance 
> fasting hyperglycemia
> increased lipid triglycerides 
> decreased HDL levels 
> hypertension

Human Physiology 2 - Unit 3 - Zach H. (9 decks)

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