Bile & Biliary System Flashcards
What does CCK stand for?
What is it and what does it do in the body?
Cholecystokinin.
It is a peptide hormone and acts as a gall bladder contractor, which causes bile to be released into the duodenum. It also causes pancreatic pro-enzyme release.
Where is CCK synthesised and secreted?
By I-cells in the mucosal lining of the duodenum.
What triggers the duodenal I-cells to secrete CCK into the blood stream?
Fatty acids entering the duodenum from the stomach.
Which sphincter opens the common bile duct into the duodenum?
Which hormone causes this sphincter to relax?
The sphincter of oddi.
CCK.
Up to how many times more concentrated is bile in the gallbladder?
X15.
What is secretin?
What does it do in the body?
It is a hormone.
It stimulates bicarbonate rich fluid to be released into the duodenum from the pancreas and from the duodenal glands themselves into the duodenal lumen to neutralise the acidic chyme.
It also stimulates bile production in the liver.
Where is secretin synthesised and released from?
What stimulates this release?
It is synthesised and secreteted from S-cells in the mucosal lining of the duodenum.
It is stimulated to do this by low pH chyme entering the duodenum from the stomach.
Which cells in the pancreas are responsible for releasing bicarbonate rich fluid into the pancreatic duct and eventually the duodenum?
The Acinar cells.
Which glands in the duodenum are responsible for releasing bicarbonate rich fluid into the duodenal lumen?
Where are these glands located?
Brunners glands.
Proximal to (above)the sphincter of oddi (hepatopancreatic sphincter).
What happens to bile salts towards the end of the small intestine?
Give percentages.
They are re-absorbed for re-use (95%).
What does bile acid re-absorption stimulate?
Hit stimulates hepatpcytes (liver cells) to secrete more bile salts.
What specific circulation does bile acid re-absorption use?
Enterohepatic circulation.
Entero = intestinal absorptive cells Hepatic = liver
Is biliary secretion driven by blood pressure/hydrostatic pressure?
No, it is an active process requiring energy that can occur against the pressure gradient. It is independent from blood pressure.
What must accompany any secretion in order to facilitate this?
Why?
An increase in blood flow to provide nutrients and electrolytes to drive the process.
What are the smallest tubular structures that form the biliary tree?
Where are these found?
Bile canaliculi.
Found between the apical membranes of adjacent hepatocytes.
What do multiple bile canaliculi merge to form?
Terminal bile ducts.
What is the structure of the biliary tree from terminal ducts to right and left hepatic ducts.
Terminal > perilobular > interlobular > septal > lobar > R&L hepatic ducts
What is bilirubin?
A component of bile and a waste product from RBC breakdown.
How does bilirubin travel in the blood stream to the liver?
Bound to albumin.
What happens to bilirubin once it is in the liver?
It is formed into bilirubin glucuronide and secreted into the bile canaliculi.
What is normal plasma bilirubin?
What level is jaundice?
What is the obvious symptom of jaundice?
3-10mg/mL.
> 18mg/mL.
Yellowing of the mucous membranes/skin/sclera of the eye.
What does bile do once it has been secreted into the small intestine?
Digests lipids and aids with their absorption.
What is the breakdown and absorption process for glycerol and short chain fatty acids?
They can penetrate the enterocytes and cross the cell to be directly absorbed into the blood capillary supplying that particular villus.
cholesterol, monoglycerides and long chain fatty acids can not freely penetrate enterocytes. By what process do these molecules enter enterocytes?
They require the aid of mixed micelle ‘shells’ formed of bile salts surrounding the molecules. This allows them to enter the enterocytes.
Are bile salts hydrophilic or hydrophobic?
They are both! They are aphipathic.
Once inside the enterocytes, what happens to the long chain fatty acid molecules?
They are broken down by rough ER, smooth ER, and the Golgi to form chylomicrons.
What happens to chylomicrons in the enterocytes?
They are exocytosed into lacteal vessels (lymphatic capillaries) which then travel to the thoracic duct and finally into the generic circulation.
What is the process called by which bile acids are reabsorbed and recirculated for reuse, meaning the whole ‘pool’ of body bile is not resynthesised everyday?
The enterohepatic circulation of bile acids.
