6. Liver & Biliary Tree Flashcards
What are zymogen granules?
Why are they useful?
Membrane-bound bodies that contain enzyme precursors (usually inactive)
Allow sorting & packing of digestive enzymes (esp in pancreas)
List the digestive enzymes released by the pancreas
Proteases: trypsin chymotrypsin elastase carboxypeptidase
Amylases
Lipases
Give examples of pancreatic enzymes that are produced in their inactive forms
What is the reason for this?
Trypsinogen
Chymotrypsinogen
If these proteases released in their active form, would digest the pancreas, causing destruction & Pancreatitis
What hormone stimulates the release of enzyme rich pancreatic secretions?
Cholecystokinin (CCK)
What hormone stimulates bicarbonate rich pancreatic secretions?
Secretin
List 4 major functions of the liver
Energy metabolism
Detoxification
Plasma protein production
Production/secretion of bile
What does bile comprise of?
Bile salts Bile pigments (e.g. Bilirubin) Cholesterol Phospholipids Electrolytes Water
Whats the difference between bile acid dependent & bile acid independent parts of bile?
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)
Give 2 examples of bile acids
Cholic acid
Chenodeocycholic acid
Describe the pathway involved in the enterohepatic recirculation of bile acids
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.
What percentage of bile acids are recycled?
95%
What structural feature of bile acids enables them to emulsify fat?
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
What is the purpose of emulsifying digested fats?
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
What is a Micelle?
Aggregates of: fatty acids, cholesterol, fat soluble vitamins & phospholipids
Surrounded by bile acids.
Form as result of emulsifying action of bile acids
What are the functions of the gallbladder?
To store & concentrate bile
To release bile when needed (i.e. When chyme enters duodenum)
What hormone is involved in causing the gallbladder to contract?
Cholecystokinin (CCK)
Has other functions, incl relaxation sphincter of Oddi
What is the consequence of inadequate bile/pancreatic lipase secretion?
Fat digestion largely unsuccessful:
Dietary consequences: lack absorption of fat soluble vits
Steatorrhoea (pale, fatty, foul smelling stools)
What is the difference between the anatomical & functional lobes of the liver?
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)
Which structures help to suspend the liver in the abdomen?
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)
Which other structures derive arterial blood supply from the hepatic artery?
Cystic artery branch supplies:
Cystic duct
Gall bladder
Common bile duct
Explain the terms ‘hepatic lobule’ & ‘hepatic acinus’
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)
Draw the structure of the biliary tree
https://www.studyblue.com/notes/note/n/52-gallbladder-and-biliary-tracts/deck/6519297
