Lecture 1 Flashcards
What does the GI tract add to a meal? Why?
Water, ions, enzymes to create an aqueous solution of molecules suitable for absorption and transport around the body.
How much does the daily oral intake, combined with salivary, gastric, biliary and pancreatic secretions contribute to the fluid that enters the upper gastrointestinal tract each day?
8.5L
What is the daily faecal fluid excretion amount?
Less than 150 mL
What is the net absorption of the GI tract?
> 8L per day
Where does 90% of the net absorption occur in the GI tract?
Small intestin
What is the max amount of water the colon can absorb?
2 to 3 L a day
What are gut commensal bacteria?
Bacteria that live in the gut and are important for gut health
How many bacteria are within the gut?
Trillions, large numbers diverse species
Describe the variation of the gut bacteria
Vary widely between individuals, but stay fairly constant within an individual unless exposed to various stresses in the gut.
What are the protective functions of gut bacteria?
Barrier:
- Competes against growth of pathogenic organisms
- Influences expression of genes on intestinal epithelium
- Regulates permeability of tight junctions
Immunity
- Drives IgA production
Describe the tolerance of the immune system to gut bacteria
The immune system is tolerant towards commensal bacteria and non-harmful antigens. Problems with this tolerance lead to allergies and inflammatory bowel disease.
What happens to the undigested carbs that enter the colon?
Fermented by commensal bacteria, producing short chain fatty acids. Flatus is a by-product.
What are short chain fatty acids an important source of?
Energy and nutrients
Why might some people suffer more from bloating and distension?
Certain types of gut flora will produce certain types of fatty acids, which produce gas as a by-product.
How can gut microbiota influence metabolism?
Certain compositions of gut microbiota may produce favourable SCFA’s that have a positive effect on metabolism, leading to increased chance of obesity and diabetes.
How can inflammation alter the normal flora balance?
An individual who has had severe gastroenteritis may develop post-infectious irritable bowel syndrome. This is when there is a disturbance in the balance of the gut flora and as a result, the individual is left with this imbalance after infection.
How can antibiotic use alter normal flora balance?
- Can lead to antibiotic associated diarrhoea
- Can cause Clostridium difficile infection
What are the two main causes of the alteration of normal flora balance?
Inflammation and antibiotics
Describe how Clostridium can infect the gut
Clostridium is a bacterium that in healthy people, does not tend to be pathogenic, but in people who are immunosuppressed or elderly, who then take courses of antibiotics, healthy bacteria is suppressed and Clostridium is allowed to proliferate, causing diarrhoea and infection.