Liver and the Biliary Tract Flashcards
(76 cards)
What is the composition of bile?
- Bile acids and bile salts
- Water (95%)
- Electrolytes
- Cholesterol
- Phospholipids
- Conjugated bilirubin
- Bile pigments
- Enzymes
- Vitamins
- Heavy metals
Where is bile formed?
The hepatocytes of the liver
What is bile and it’s pH?
A greenish-yellow alkaline that is stored and concentrated in the gallbladder.
pH7-8
What is the action of bile on fat?
- Acts as a detergent to fats - emulsifies large fat particles into smaller fat particles and form micelles to be attacked by lipase in pancreatic juice
- Aid transport of digested fat end-products to / through intestinal mucosal membrane
Why is bile a better emulsifier than bile acids?
Bile is amphipathic - both hydrophilic and hydrophobic parts
What are the functions of bile? (3)
- Aids digestion and absorption of fat (detergentation)
- Means for excretion for bilirubin (end product of haemoglobin destruction) and excess cholesterol synthesised by liver cells
- Exerts hormone-like effect to influence intestional metabolic pathways
What role does the gallbladder have in bile formation?
Stores and concentrates bile about 5 times.
What are bile acids formed from?
Cholesterol
What are the main primary bile acids
Cholic acid
Chenodeoxycholic acid
What happens to primary bile acids?
They are conjugated to bile salts by the addition of an amino acid group. They are then actively transported from the hepatocyte.
Once bile salts are formed, where do they get transported to?
Once the leave the liver, they travel through the hepatic duct and the common bile duct. Here, they either travel directly to the duodenum (where they act) or to the gallbladder via the cystic duct.
What stimulates gallbladder contraction and Sphincter of Oddi relaxation?
Vagal stimulation
CCK - Cholecytokinin
This is released from duodenal enteroendocrine cells in response to luminal fat presence.
How would you describe the contractions of the gallbladder?
Rhythmic contractions of gallbladder transmit peristaltic waves down common
What is the role of CCK in the bile system?
It promotes bile release into the duodenum. It’s released by enteroendocrine cells of the duodenum due to presence of luminal fat.
It causes gallbladder rhythmic contractions (contraction of the smooth muscle of the gallbladder) and relaxation of the Sphinter of Oddi (allowing bile into the duodenum).
What mediates relaxation of the gallbladder and closure of the sphincter of odds?
sympathetic nerves and the gut hormones Vasoactive Intestinal Polypeptide (VIP) and Somatostatin.
What % of bile acids recirculate and are recycled?
- 85%
- 90%
- 95%
- 99%
95%
Describe the enterohepatic circulation.
This is the circulation of bile substances (bile acids/bilirubin) and drugs. Bile acids are secreted from the liver in bile which enters the small intestine. They are then reabsorbed by enterocytes (mainly in the ileum) by active transport. They are then transported to the liver sinusoids via the portal vein.
The liver produces more bile acids to compensate.
What facilitates the transport of bile acids back to the liver?
Albumin. They are bound to albumin in blood.
What is the order of the biliary tree from smallest to largest?
Biliary canaliculi Interlobular ducts Septal bile ducts Intrahepatic ducts R. and L. hepatic ducts Common hepatic duct Common bile duct
Explain the path of the common bile duct (location).
It passes behind the duodenum and through the head of the pancreas. It joins the main pancreatic duct and this opens into the 2nd part of the duodenum (descending d.).
Terminology : Cholecystitis
Gallbladder inflammation
Terminology: Cholelithiasis
Gallstones within the gallbladder
Terminology: Cholecystectomy
Removal of the gallbladder
Terminology: Cholangitis
Gallstone within a bile duct