Intestine Physiology Flashcards
What senses content of the duodenum
- Vagal afferents
- I cells and S cells (apical surface)
I cells secretion
CCK
S cells secretion
Secretin
What do I cells sense
Fat/protein in duodenum lumen
What do S cells sense
pH (HCl)
CCK and secretin functions
Inhibit gastric emptying
Inhibit gastric acid secretion
Enterochromaffin cell secretion
Serotonin
How do anti-nausea meds work
Decreased serotonin (some by inhibiting enterochromaffin)
Enterochromaffin-like cell secretion
Histamine
Coeliac Genetic Rule-out Test
Two genes that almost all Coelaic have = rules out if negative (but non Coelaic also have it, so doesnt confirm Coelaic if positive)
Coeliac Symptoms
Can be anything!
Mostly IBS, nausea, vomiting, steatorrhoea etc
Coeliac Blood Test
Anti-TTG IgA
- Must be eating gluten when doing it = can be harmful
Gold standard for coeliac
Biopsy of small intestine
- Take from many (8) locations
Even if asymptomatic why should Coelaics not have gluten
Inflammation builds over time = in long term as elderly will lead to malabsorption problems in the small intestine
- Micronutrients first
Genetic markers for Coelaic
DQ2 DQ8
DGBI
Disorder of gut-brain interaction
- Tests normal but still symptoms and disease
IBS location
Any part of the GI tract
Causes of IBS
Many reasons (Microbiome, stress, mucosa etc), not 100% sure
Main cause is visceral hypersensitivity
Microbiome of IBS
Increased enterobacteriacaea
IBS severity
Low mortality
Very high morbidity - time off work, social stigma
IBS symptom criteria
- Recurrent abdominal pain
- Changes with defecation
- Change in stool consistency (Bristol chart)
Must be chronic (3-6 months)
Types of IBS
IBS-C (constipation, hard stools)
IBS-D (diarrhoea, watery stools)
IBS-M (mixed, hard and watery stools)
IBS-U (unclassified)
What symptoms suggest it might be something more than IBS
Rectal bleeding
Iron deficiency
Weight loss
Vomiting
Familial history of other disease eg Coelaic, colorectal cancer
IBS Management
- Explain no evidence of cancer, inflammation
- Don’t say its all in your head, say “Sensitive gut”
FODMAP Diet
Fermentable sugars
If IBS what diet should you consider
Low FODMAP (but dont cut out all FODMAP as need a diverse diet)
Why might you give someone with ‘diarrhoea’ laxatives / fibre
They have hard stools blocking the colon, and only the watery stools can actually get out. But the root of the problem is the constipation from hard stools
Gut-brain neuromodulators
TRC
SSRI
Anti-depressants change the way your body responds to discomfort
IBD vs IBS
Inflammable Bowel Disease v Irritable Bowel Syndrome
IBD risk groups
30s, and 60s
Non-Maori
Cause of IBD
Environmental factors in genetically susceptible individuals
- Western diet
- Antibiotics in childhood
- Smoking Crohn’s
Symptoms of IBD
Diarrhoea - frequency, urgency
Blood in stool
Tenesmus
Tenesmus
Incomplete defecation
Where else does IBD present other than the bowel
Eyes, skin, joints
Types of IBD
Ulcerative Colitis
Crohns
Ulcerative Colitis
Limited to colon
Inflammation down whole colon
Crohn’s
Any part of the GI tract, mainly colon and ileum
Inflammation
Narrowing
Fistula = joining
Perianal fissures
Different symtpoms of Chrons and Ulcerative colitis
UC - Always diarrhoea, bleeding
Chrons - Not always diarrhoea, bleeding = harder to detect
Normal stools on the Bristol Stool Chart
2-4
As Bristol Stool number increases, what happens to consistency
More loose
Acute Diarrhoea cause
Infection!
Chronic diarrhoea types
- Inflammatory
- Osmotic
- Secretory
- Fatty
If blood in diarrhoea what type is it
Inflammatory
Campylobacter causes ______ diarrhoea
Inflammatory
Giardia causes ______ diarrhoea
Osmotic
E. coli causes ____ diarrhoea
Secretory
Main cause of acute diarrhoea
Campylobacter
Inflammatory Diarrhoea cause
Inflammation of the bowels = rupture to mucosa
- eg IBD Coeliac cancer
What causes osmotic diarrhoea
Fluid drawn into lumen (eg. By lactose, IBS, Coeliac)
What causes secretory diarrhoea
Bile acid in the lumen = H2O secretion increased = diarrhoea
What causes fatty diarrhoea
Undigested fat in stool
SIBO stands for
Small intestinal bacterial overgrowth
What types of diarrhoea caused by SIBO
All
Ileostomy
Ilium diverted to outside of body, circumvent the anus = need holding bag
How much fluid consumed / excreted daily
8.5L consumed
6.5L absorbed by small int
2L absorbed by large int
~100mL excreted
Small intestine electrolyte secretion
HCO3-
Large intestine electrolyte secretion
K+ and HCO3-
Transcellular movement
Across two membranes, therefore must be active across at least one
Solutes
Paracellular Movement
Passive via tight junctions
Where does absorption of water mostly occur
Jejunum
How does Na+ absorption occur
Exchanges and cotransporters down conc grad into cell
How does Cl- absorption occur
Follows Na+ absorption for charge balance
By exchangers (with HCO3-) and absorption on its own
What does CFTR do
Active channel that moves Cl-
What regulates absorption and secretion
Mainly Aldosterone
Also enteric nervous system, paracrine hormones etc
Difference between secretory and osmotic diarrhoea
Secretory =contents added to the lumen eg Na+ causing solvent drag
Osmotic = contents remain in the lumen from malabsorption
How does oral rehydration therapy work
Na+ and glucose absorbed
= Cl- absorbed to balance charge
= H2O absorbed due to osmotic gradient
= Less diarrhoea
What is a polyp
Circumscribed growth projecting above the mucosa
Can be neoplastic or not
Types of non neoplastic polyps
Hyperplastic (common)
Inflammatory
Adenoma
Pre-malignant polyp
Types of adenomas
Tubular (common)
Villus
Tubulovillous
Main risk factor for neoplastic adenoma becoming carcinoma
Size of the polyp (larger = increased risk)
Adenocarcinoma leads to which nutrient deficiency
Iron, due to chronic bleeding
How to stage tumours
TNM
T - Extent of invasion of bowel wall
N - Number of lymph nodes
M - Metastatic?
Familial Polyposis Syndromes lead to higher rates of carcinomas because
Higher likelihood of adenoma becoming carcinoma (no increase in numbers of polyps themselves)
