Bile & Biliary System

Question 1

What does CCK stand for?

What is it and what does it do in the body?

Answer 1

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.

Question 2

Where is CCK synthesised and secreted?

Answer 2

By I-cells in the mucosal lining of the duodenum.

Question 3

What triggers the duodenal I-cells to secrete CCK into the blood stream?

Answer 3

Fatty acids entering the duodenum from the stomach.

Question 4

Which sphincter opens the common bile duct into the duodenum?

Which hormone causes this sphincter to relax?

Answer 4

The sphincter of oddi.

CCK.

Question 5

Up to how many times more concentrated is bile in the gallbladder?

Answer 5

X15.

Question 6

What is secretin?

What does it do in the body?

Answer 6

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.

Question 7

Where is secretin synthesised and released from?

What stimulates this release?

Answer 7

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.

Question 8

Which cells in the pancreas are responsible for releasing bicarbonate rich fluid into the pancreatic duct and eventually the duodenum?

Answer 8

The Acinar cells.

Question 9

Which glands in the duodenum are responsible for releasing bicarbonate rich fluid into the duodenal lumen?

Where are these glands located?

Answer 9

Brunners glands.

Proximal to (above)the sphincter of oddi (hepatopancreatic sphincter).

Question 10

What happens to bile salts towards the end of the small intestine?

Give percentages.

Answer 10

They are re-absorbed for re-use (95%).

Question 11

What does bile acid re-absorption stimulate?

Answer 11

Hit stimulates hepatpcytes (liver cells) to secrete more bile salts.

Question 12

What specific circulation does bile acid re-absorption use?

Answer 12

Enterohepatic circulation.

Entero = intestinal absorptive cells
Hepatic = liver

Question 13

Is biliary secretion driven by blood pressure/hydrostatic pressure?

Answer 13

No, it is an active process requiring energy that can occur against the pressure gradient. It is independent from blood pressure.

Question 14

What must accompany any secretion in order to facilitate this?

Why?

Answer 14

An increase in blood flow to provide nutrients and electrolytes to drive the process.

Question 15

What are the smallest tubular structures that form the biliary tree?

Where are these found?

Answer 15

Bile canaliculi.

Found between the apical membranes of adjacent hepatocytes.

Question 16

What do multiple bile canaliculi merge to form?

Answer 16

Terminal bile ducts.

Question 17

What is the structure of the biliary tree from terminal ducts to right and left hepatic ducts.

Answer 17

Terminal > perilobular > interlobular > septal > lobar > R&L hepatic ducts

Question 18

What is bilirubin?

Answer 18

A component of bile and a waste product from RBC breakdown.

Question 19

How does bilirubin travel in the blood stream to the liver?

Answer 19

Bound to albumin.

Question 20

What happens to bilirubin once it is in the liver?

Answer 20

It is formed into bilirubin glucuronide and secreted into the bile canaliculi.

Question 21

What is normal plasma bilirubin?

What level is jaundice?

What is the obvious symptom of jaundice?

Answer 21

3-10mg/mL.

> 18mg/mL.

Yellowing of the mucous membranes/skin/sclera of the eye.

Question 22

What does bile do once it has been secreted into the small intestine?

Answer 22

Digests lipids and aids with their absorption.

Question 23

What is the breakdown and absorption process for glycerol and short chain fatty acids?

Answer 23

They can penetrate the enterocytes and cross the cell to be directly absorbed into the blood capillary supplying that particular villus.

Question 24

cholesterol, monoglycerides and long chain fatty acids can not freely penetrate enterocytes. By what process do these molecules enter enterocytes?

Answer 24

They require the aid of mixed micelle ‘shells’ formed of bile salts surrounding the molecules. This allows them to enter the enterocytes.

Question 25

Are bile salts hydrophilic or hydrophobic?

Answer 25

They are both! They are aphipathic.

Question 26

Once inside the enterocytes, what happens to the long chain fatty acid molecules?

Answer 26

They are broken down by rough ER, smooth ER, and the Golgi to form chylomicrons.

Question 27

What happens to chylomicrons in the enterocytes?

Answer 27

They are exocytosed into lacteal vessels (lymphatic capillaries) which then travel to the thoracic duct and finally into the generic circulation.

Question 28

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?

Answer 28

The enterohepatic circulation of bile acids.