Week 2.10 - Bile and Gallbladder Flashcards
What are bile pigments?
come from breakdown of haemoglobin in old/damaged erythrocytes in the liver. breakdown secreted into bile, forming yellow bile
What is billirubin and what happens to it?
yellow bile. secreted into intestine where it is modified by bacterial enzymes and forms brown faeces. rest is reabsorbed and excretes as yellow urine
How are bile acids made?
synthesised in the liver from cholesterol oxidised to bile acids using cytochrome P450
How much bile acids do we make each day?
0.5g
how are bile salts made? why?
bile acids conjugated with other acids in the liver like glycine and taurine.
increases solubility of bile acids.
Where do bile salts go after they are synthesised?
through hepatic duct, then cyctic duct to gallbladder or common bile duct towards intestine
How are bile salts reabsorbed?
in intestine reabsorbed back into circulation. reach liver again through hepatic portal vein. 95% recycled.
What is the cycle of bile?
bila acid - bile salt in liver - bile duct -> duodenum -> jejunum -> ileum -> hepatic portal vein -> liver… etc
What is the structure of the gallbladder?
saclike 8cm long 4cm wide
- innermost rugae mucosa
- muscularis smooth muscle
- serosa layer.
What controls bile secretion?
sphincter of oddi when contracts pushes bile back into gallbladder for storage, where it is concentrated 5-20x. when opens bile is secreted and gallbladder empties.
How is bile able to be concentrated?
Na+ in gallbladder epithelium leaves cell when bile enters, causing water to exit alongside due to high osmotic pressure of Na+.
What hormones control contraction of sphincter of oddi?
CCK and secretin
How is CCK release initiated?
fats and amino acids in duodenum induce CCK release
How is secretin release initiated?
acid in the duodenum initiates release of secretin
What does secretin do?
- lowers gastrin secretion, decreasing gastric emptying
- releases HCO3- from duodenal cells, pancreas and liver
- these neutralise the acid causing halt in secretin secretion
