Lecture 1 Flashcards
Luminal organs
Oesophagus
Stomach
Small and Large intestine
Hepato-bilary system
Liver
Pancreas
Gall bladder
Reffered pain
GI tract, depending on where pain originates from, it is referred to different areas because visceral pain felt by gut, is often is same pathway as somatic nerves.
- often tend to correlate with dermatomes
- generally tends to be felt in the Upper, Mid or Lower Abdomen
T8-9 Referred Pain
Liver Gallbladder Spleen Stomach Duodenum Pancreas Heart + Aorta
T10-11
Small bowel Appendix Caecum Ascending colon to mid transverse Testis Renal Tract
T12-L1 Referred Pain
Large Bowel
Bladder
Prostate (male) or Uterus+Adnexa (female)
Gut Barrier function
barrier against foreign invaders (bacteria, pathogen)
Lubrication - goblet cells release mucous (barrier/prevent bacterial permeation)
Immune cells form gut barrier
Epithelial cells: Goblet-mucous secretion, Paneth cells-protective enzymes. Tight junction-less permeation of large molecules through.
Deeper: Immune cells (T and B) + Lymphoid follicles
Role of gastric acid
- Sterilize food (gut exposed to external triggers/factors that are potentially harmful)
- Initial digestion
- Only bacteria known to survive in stomach (Helicobacter Pylori-pathogen causing stomach ulcers)
Gut Microbiota
Commensal Bacteria/Gut flora- live in gut and good for gut health- probiotics
Large numbers(trillions), diverse species
Most cannot be cultured/identified (due to be so diverse)
Vary widely between individuals (dont have identical type of gut bacteria) , but stay fairly constant within an individual (unless exposed to gut stresses)
Stomach + DJI (proximal+distal) + Colon
Order and Distribution of Gut Microbiota
Stomach: 0-10^2 (fairly sterile)
Duodenum: 10^2
Jejunum: 10^3
Prox. Ileum: 10^3
Dist. Ileum: 10^7 -10^9
Colon: 10^11-10^12 (highly populated w. bacteria)
-gut bacteria predominantly lives in colon. has regulation in determining symptoms in some people
Protection against pathogens re barrier function
- Competes against growth of pathogenic organisms (important as gut is exposed to large number of pathogens, therefore needs to be able to protect itself)
- Influences expression of genes on intestinal epithelium (certain cells promoted to increase, depending on state of gut flora)
- Regulates permeability of tight junctions (selective permeability)
- mucosal barrier
- has gut flora, which protects invasion of foreign organisms (competes against foreign pathogens)
Protection against pathogens re balance of both Immunity + Tolerance
- Complex inter-relationship
- Multiple components of the gut and systemic immune system
- Drives IgA production
- Tolerance to commensal bacteria and to non-harmful antigens (allergies, inflammatory bowel disease) (exposed to a number of foreign pathogens, but doesn’t illicit immune response against all these organisms)
- degree of tolerance important, w. loss of tolerance develop diseases (inflammatory bowel disease) and allergies (celiac disease) (must protect and tolerate BOTH otherwise will be constant state of inflammation - Immunity and Tolerance balance)
- balance of immunity and tolerance is an important driver of diseases
Effects on Metabolism
Undigested carbohydrates that enter colon are fermented by commensal bacteria, producing short-chain fatty acids (acetate, propionate, butyrate)
-Flatus is a bi-product (gas) –> driver of irritable bowel syndrome (component driven by gut bacteria)
SCFAs source of energy/nutrients for bowel
-gut flora from obese mouse put into skinny mouse will make skinny mouse obese
Certain compositions of gut microbiota may produce favourable SCFAs that have positive effects on metabolism (obesity, diabetes) - individuals produce different SCFA, hence why some people suffer from certain symptoms (bloating and distention) whilst other people dont
Alterations in normal flora balance
- Inflammation: e.g. patient w severe gastroenteritis may develop post-infectious irritable bowel syndrome- inflammation has disturbed balance of gut flora, even after infection, causing persistent symptoms
- Antibiotic use: (esp chronic use)
-Antibiotic-associated diarrhoea (can cause a number of GI symtoms including diarrhoea)
-Clostridium difficile infection. Clostridium is bacteria that isnt normally pathogenic in healthy people. But in the elderly or immunosuppressed people who take antibiotic courses, antibiotics suppress normal healthy gut flora, clostridium proliferates, causing diarohea and infection
Role of Probiotics: reintroduction of health bacteria to cure these disturbances
Key GI functions
Digestion
Absorption: min, nutrients and vitamins
Excretion
Role of Liver
