6. Liver & Biliary Tree

Question 0

What are zymogen granules?

Why are they useful?

Answer 0

Membrane-bound bodies that contain enzyme precursors (usually inactive)

Allow sorting & packing of digestive enzymes (esp in pancreas)

Question 1

List the digestive enzymes released by the pancreas

Answer 1

Proteases: 
trypsin
chymotrypsin
elastase
carboxypeptidase

Amylases

Lipases

Question 2

Give examples of pancreatic enzymes that are produced in their inactive forms
What is the reason for this?

Answer 2

Trypsinogen
Chymotrypsinogen

If these proteases released in their active form, would digest the pancreas, causing destruction & Pancreatitis

Question 3

What hormone stimulates the release of enzyme rich pancreatic secretions?

Answer 3

Cholecystokinin (CCK)

Question 4

What hormone stimulates bicarbonate rich pancreatic secretions?

Answer 4

Secretin

Question 5

List 4 major functions of the liver

Answer 5

Energy metabolism
Detoxification
Plasma protein production
Production/secretion of bile

Question 6

What does bile comprise of?

Answer 6

Bile salts
Bile pigments (e.g. Bilirubin)
Cholesterol
Phospholipids
Electrolytes
Water

Question 7

Whats the difference between bile acid dependent & bile acid independent parts of bile?

Answer 7

Bile acid dependent:
secreted by hepatocytes
contains bile acids & bile pigments

Bile acid independent:
secreted by duct cells (in bile ducts)
composed of alkaline juice containing HCO3- (similar to pancreatic alkaline secretions)

Question 8

Give 2 examples of bile acids

Answer 8

Cholic acid

Chenodeocycholic acid

Question 9

Describe the pathway involved in the enterohepatic recirculation of bile acids

Answer 9

Bile acids (as part of bile) delivered to 2nd part of duodenum, having passed thru biliary tree

Bile acids lass thru gut until reabsorbed in terminal ileum.

Transported back into portal vein.

Drain back into liver.

Question 10

What percentage of bile acids are recycled?

Answer 10

95%

Question 11

What structural feature of bile acids enables them to emulsify fat?

Answer 11

Bile acids are facial amphipathic: contain both hydrophobic & hydrophilic (polar) faces.
Cholesterol-derived portion of bile acids: 1 face hydrophobic & 1 face hydrophilic
Amino acid conjugate: hydrophilic (polar)

Amphipathic nature enables bile acids to carry out:
Emulsification of lipid aggregates
Solubilisation & transport of lipids in aqueous environment

Question 12

What is the purpose of emulsifying digested fats?

Answer 12

Blending fat & water (that dont normally mix) in the gut.
Increases surface area.
So larger proportions dispersed in water.
Makes it easier for Lipases to digest fat

Question 13

What is a Micelle?

Answer 13

Aggregates of: fatty acids, cholesterol, fat soluble vitamins & phospholipids
Surrounded by bile acids.

Form as result of emulsifying action of bile acids

Question 14

What are the functions of the gallbladder?

Answer 14

To store & concentrate bile

To release bile when needed (i.e. When chyme enters duodenum)

Question 15

What hormone is involved in causing the gallbladder to contract?

Answer 15

Cholecystokinin (CCK)

Has other functions, incl relaxation sphincter of Oddi

Question 16

What is the consequence of inadequate bile/pancreatic lipase secretion?

Answer 16

Fat digestion largely unsuccessful:
Dietary consequences: lack absorption of fat soluble vits
Steatorrhoea (pale, fatty, foul smelling stools)

Question 17

What is the difference between the anatomical & functional lobes of the liver?

Answer 17

Anatomical division (right, left, caudate, quadrate) of little significance

Division into lobes & segments had functional & practical implications: each lobe & segment has own:
vascular supply (branch of hepatic portal vein & hepatic artery)
element of intra-hepatic biliary sys (bile duct/ductule)

Question 18

Which structures help to suspend the liver in the abdomen?

Answer 18

Hepatic veins: join IVC near passage thru diaphragm

Tone of anterior abdominal wall muscles ‘push’ liver up & under diaphragm, assisting with holding up in position

Minor role from:
Coronary, right, left & triangular ligaments
(peritoneal reflections btw upper surface if liver & lower surface of abdomen)

Question 19

Which other structures derive arterial blood supply from the hepatic artery?

Answer 19

Cystic artery branch supplies:
Cystic duct
Gall bladder
Common bile duct

Question 20

Explain the terms ‘hepatic lobule’ & ‘hepatic acinus’

Answer 20

Hepatic lobule:
Organisation of hepatic parachymal cells (hepatocytes) around vascular elements.
Has a tributary of:
hepatic vein (central vein) @ axis
Portal triads @ periphery (hepatic portal vein branch, hepatic artery branch, element of intrahepatic biliary system- bile duct)

Hepatic acinus:
also based on functional parameters, but focuses on metabolic & pathologic considerations.
An elliptical area with short axis, spanning 2 portal triads & long axis, defined btw 2 central veins that form outermost poles of acinus.
Short axis contains portal venous & hepatic arterioles, draining into hepatic sinusoids lying btw hepatocytes.
Sinusoids drain into central veins (terminal hepatic venules)

Question 21

Draw the structure of the biliary tree

Answer 21

https://www.studyblue.com/notes/note/n/52-gallbladder-and-biliary-tracts/deck/6519297