GI9 - The Liver and the Pancreas

Question 1

How the duodenum deals with the features of chyme leaving the stomach

Hypertonic (controlled)
Low pH
Partially Digested

Answer 1

1. ) Reducing Tonicity - chyme is hypertonic because the stomach wall is impermeable to water
   - duodenum is permeable to water so can dilute chyme
2. ) Controlled Chyme Release - small amounts of chyme are relased into the duodenum at a time
   - this prevents too much water entering the duodenum which helps to prevent a drop in blood pressure
3. ) Increasing pH - duodenum secretes secretin
   - secretin stimulates pancreas to release aq HCO3-
4. ) Digestion - duodenum secretes CCK
   - CCK stimulates pancreas to release enzymes
   - CCK stimulates gallbladder to release bile and relaxes sphincter of oddi to allow the bile to enter duodenum

Question 2

4 features of bile

Synthesis
Contents
Storage
Function

Answer 2

1. ) Synthesis - by hepatocytes and duct cells in the liver
   - continuously produced but only needed intermittently
2. ) Contents - bile salts (60%), pigments, alkaline juices
   - salts and pigments are secreted by hepatocytes
   - alkaline juices are secreted by cells lining the bile ducts which is stimulated by secretin
3. ) Storage - stored in the gallbladder which also concentrates bile by removing water/ions
   - released into the common bile duct –> duodenum
   - release is stimulated by CCK
   - if the gallbladder is overfilled, it can lead to gallstones

4.) Function - emulsifies fats in the duodenum to aid digestion by lipases secreted by the pancreas

Question 3

5 features of bile salts

What Are They?
Structure
Function
Micelles
Recycling

Answer 3

1. ) Conjugated Bile Acids - bile acids are made and conjugated to AAs in the liver due to low solubility
   - bile salts are more soluble at duodenal pH than bile acids

2.) Amphipatic Structure - have an hydrophilic and hydrophobic end which acts on oil/water interface

3. ) Emulsifies Dietary Lipids - increases SA for lipases
   - bile salts then create micelles w/ lipid breakdown products: cholesterol, monoglycerides, free FAs

4.) Micelles - transport hydrophobic products of lipid digestions towards cells lining the gut wall

5. ) Recycling - lipids diffuse into intestinal epithelial cell but bile salts remain the the gut
   - they are then reabsorbed in the terminal ileum and returned to the liver in portal blood

Question 4

3 features of steatorrhoea

Definition
Cause
Appearance

Answer 4

1.) Definition - excretion of undigested fat in faeces due to fat staying in the intestines

2. ) Cause - problems with bile salts or pancreatic lipases
   - not secreted in adequate amounts
   - exocrine pancreatic insufficiency

3.) Appearance - faeces is pale, floating, foul smelling