Lectures Flashcards
What are macro and micro nutrients?
Macro nutrients - fats, carbs & protein
Micro nutrients - vitamins, minerals & trace elements
Which are the fat soluble vitamins?
Where are they absorbed?
Where are they stored?
A, D, E & K
Absorbed in SI in presence of fat
Stored in body tissues.
Which are water-soluble vitamins? Where are they absorbed?
C, B1, B2 & Folate - absorbed SI - generally not stored in the body.
What is the function of Vitamin A? Where is it found?
Function - immunity, night vision, dec risk of bone fractures in older Ps
Found - liver, offal, oily fish, eggs, dairy & fortified foods.
What is the function of Vitamin D? Where is it found?
Used in Ca absorption & bone mineralisation. Deficiency –> rickets.
Found - cod liver oil, oily fish, eggs, liver, fortified food (not UK milk)
What is the function of Vitamin E? Where is it found?
Eyes, skin, immune system, protection of CSM from free radicals & lipoproteins, prostaglandin synthesis & DNA synthesis.
Found - plant oils, nuts, seeds & wheatgerm (cereals)
What is the function of Vitamin K? Where is it found?
Used for blood clotting, healing & poss bone health
Found - green leafy veg, veg oils, cereal grains, eggs, small amt in meat & dairy
FYI - DO NOT TAKE IF ON ANTI COAGS
What is the function of Vitamin C?
Where is it found?
- Antioxidants
- Collagen synthesis
- Peptide hormone activation
- Bile
- Metabolism of drugs & carcinogens
- Inc absorption of iron if in same meal.
Found: citrus, peppers, strawberries, blackcurrants, broccoli, brussel sprouts, sweet & normal potatoes.
CANT BE STORED IN THE BODY
What is the function of Vitamin B1?
Where is it found?
Release of energy from food + nervous system.
Found: Peas, pulses, nuts, some fruits (banana, orange), wholegrain bread, cereals, liver, yeast, milk
What is the function of B12?
Where is it found?
Erythropoiesis, NS, releases energy from food, in use of folate
Found: Meat, fish, milk, cheese, eggs & fortified cereals
What is the function of folate?
Where is its found?
Folate = folic acid (man made version)
Used in maintaining health RBCs, prevents neural defects in pregnancy
Found - broccoli, Brussels sprouts, peas, green leafy veg, chickpeas, kidney beans, liver, fortified cereals
What Is the function of calcium?
Where is it found?
Used to make rigid bones & teeth, muscle contractions, heart beat, blood clotting
Found - dairy, leafy green veg, bread & fortified flour, fish with bones
What is sodium used for?
Balance of fluid levels - adults need <6g/day. Too much = hypertension, heart attacks
Where is iron found?
Liver, red meat, beans, nuts, dried fruit, fortified cereals, soy bean flour.
What is K used for?
Where is it found?
Used for fluid balance & heart muscle contraction
Found - bananas, oranges, some veg, beans & pulses, nuts & seeds, coffee, dark choc, you, potatoes, LO salt.
Older Ps - kidneys may remove less K.
What additional requirements are there for diet in pregnancy?
Additional energy & thiamine needed in 3rd trimester
FA - take for first 12 weeks
Take daily Vitamin D throughout
Avoid cod liver oil / Vitamin A supplements
Vegans - need a DHA supplement (Omega3)
What additional dietary requirements do breastfeeding women have?
Limit caffeine, inc energy & vitamins Daily Vit D Restrict oily fish to x2 / week - pollutants Peanuts ok If vegan - Zn can be low.
Remember psychological impact of breastfeeding.
What additional dietary requirements do children have?
No eat well plate under 2.
Need Vitamin A, C & D supplements every day.
Growth spurts - big energy requirement increases.
Adolescents - higher Ca and P requirements than adults
What is the landmark division between upper & lower GIT?
Suspensory ligament of duodenum = ligament of Treitz.
What are the accessory organs of the GIT?
Tongue Teeth Salivary glands Gall bladder Pancreas Liver
What forces propel food?
Peristalsis, gravity + lower abdominal pressure - intraoesophageal pressure is higher than in abdomen - creates pressure for food to move down.
What is the anticipatory phase of digestion called?
The cephalic phase - salivary & parietal glands stimulated.
Name the four layers of GIT wall
Mucosa
Submucosa
Muscularis externa
Serosa
What are the three layers of the mucosa - and what is in each?
Epithelium - enteroendocrine & exocrine glands - lubricate & chemical breakdown
Lamina propria - CT (thin), GALT for immunity
Muscularis mucosae - circular and longitudinal muscle - moves substances in lumen in right direction
What is in the submucosa?
Dense layer of CT - contains BVs, lymph, mucus glands & Submucosal nerve plexus (controls gland secretions and localised blood flow).
What is in the muscularis externa layer?
Circular muscle, Myenteric nerve plexus (controls the muscles here) & Longitudinal muscle
What is the function of the serosa?
What is the serosa called in the oesophagus?
Secretes serous fluid into abdominal cavity - lubricates to prevent friction from adjacent organs.
Serosa in oesophagus = adventitia (thick & fibrous CT).
How do substances move through the GIT?
Coordinated smooth muscle contraction - synchronised & autonomic process
Which parts of the GIT are under voluntary control?
Upper oesophagus & external anal sphincter - both made of striated skeletal muscle.
How is the GIT adapted for motility?
Has smooth muscle w/gap junctions - fast - contracts as syncytium.
What are the 3 phases of swallowing & which CN controls each phase? Describe what happens in each.
Oral (Voluntary) - tongue - formation of bolus
Pharyngeal (pharynx) - autonomous - bolus stimulates receptors –> CN9 - triggers swallowing centre in medulla oblongata –> CN5, 9 & X –> muscular contraction of pharynx, propelling bolus down. Epiglottis closes over larynx, respiration inhibited. UOS (at pharyngoesophageal junction) relaxes for food to move into oesophagus, closes once it has passed.
Oesophageal - autonomous - intraoesophageal pressure is higher than abdominal = pressure for food to move down. Sphincters remain constricted to prevent air entering.
First peristalsis wave - bolus reaches oesophagus - receptors - muscularis externes circular muscle contracts and squeezes, longitudinal relaxes and lengthens - pulls bolus down.
Which cranial nerve supplies the roof of the mouth?
CN5
Which cranial nerve supplies the pharynx?
CN9 - GP nerve
Which cranial nerve supplies the oesophagus & stomach?
CNX - Vagus nerve
Which nerves supply the visceral organs?
Splanchnic nerves
What is the enteric nervous system?
Is the myenteric nerve plexus (motility + contraction) + submucosal nerve plexus (glandular secretions & local blood flow).
Functions independently of CNS - truly autonomous
How can the enteric nervous system be modified?
By the Autonomic nervous system:
- PSS - postganglionic fibres innervate the SM & Secretory cells (using ACh) - stimulates rest & digest via CNX
- SS - innervate ganglia - inhibits the enteric nervous system (F&F response) but stimulate BV and sphincter contraction.
Which vertebral level does the oesophagus penetrate the diaphragm?
T10
Which types of muscle are in the oesophagus?
Upper 1/3 - striated muscle - voluntary control
Lower 1/3 - smooth muscle - involuntary
Middle - mix of both
What stops air entering the oesophagus?
Contraction of sphincters.
What happens during the primary peristaltic oesophageal wave?
Primary peristaltic wave - bolus reaches oesophagus - receptors - muscularis externis - circular muscle contracts and squeezes, longitudinal relaxes and lengthens -> moves bolus downwards. Receptors sense pressure change - info to CNX - causes release of vasoactive intestinal peptide - VIP - causes relaxation of LOS & SM - relaxes and opens (and closes).
What happens during the secondary peristaltic wave?
Remaining bolus is detected by mechanoreceptors in mucosal layer -> ENS —> myenteric plexus coordinates contraction above and relaxation below - initiates 2 peristaltic wave which removes any remaining food.
Where does the oesophagus meet the stomach?
At the cardiac orifice via the cardiac sphincter - = oesophagogastric junction.
What happens to the lining of the GIT at the oesophagogastric junction?
Changes from stratified squamous epithelium (oesophagus) to columnar epithelium of stomach.
Which cells are in the pyloric part of the stomach?
Mucous neck cells and enteroendocrine cells
What controls gastric secretions and blood flow in the stomach?
The submucosal plexus
Which level of lining of stomach is responsible for peristalsis?
What is it used for?
Muscularis externa - has 3 layers of SM - outer longitudinal, middle circular and inner oblique layer.
Mixing, digestion and emptying
What are the stomach muscles innovated by?
Myenteric nerve plexus (ENS)
PSS - CNX - increases gastric secretion and motility
SS - celiac ganglion - inhibits secretion and motility
Which reflex mediates receptive relaxation when food enters the stomach?
What does it allow?
The vagovagal reflex - reduces muscle tone and allows reservoir function.
CNX
What do propulsion & retropulsion in stomach cause?
Mixing of the contents in cycles.
What stimulates and inhibits transfer of contents from stomach to duodenum?
Regulated by signals from SI.
Stimulated by ENS, ANS or hormones (motilin)
Inhibited by ANS, duodenal enterogastric reflexes and hormones (CCK)
Which is the gene responsible for CF?
CFTR
What causes CF on a cellular level?
CFTR - gene involved with Cl ion transport - can be completely blocked or partially impaired. Result = less Cl to outside of cell - therefore less water and HCO3 follows. Creates sticky mucus - can affect whole body inc. lungs, gut & fertility
How does neonatal meconium ileus occur?
CFTR gene irregularity = tubes in GIT fail to “canalise” - are either narrowed or completely obstructed. Means baby cannot poo - meconium remains in ileum.
How does CF affect the GIS?
Causes strictures / blockages in development. Sticky mucus can later cause obstruction.
Also causes blockages in liver, biliary tree & pancreas.
If a P with CF presents with vomiting, stress diarrhoea, distension & then absence of poo - what could be the diagnosis?
Blockage of the intestinal tract
What is creon?
Digestive pancreatic enzymes
Why do CF ps have greater risk of C Diff?
Are often on ABs for long time.
Will calprotectin by high or low in CF?
High
What is DIOS?
What causes it?
Treatment?
Distal Intestinal Obstruction Syndrome - thickened stool with mucus blocks intestinal tube - completely or partially.
Can be caused by too little Creon, dehydration or narrow intestine.
Rehydration, laxatives, enzymes + poss surgery.
P presents with distension, vomiting, constipation. AXR = distended proximal bowel + tinkling bowel sounds. Diagnosis?
DIOS
What is Cholecystitis?
What causes it in CF?
Inflammation of the gallbladder.
Lots of CFTR genes in gallbladder - may mean that ducts are too narrow. Lots of sticky mucus can also inc formation of gall stones + inc risk from bacteria with the mucus.
Why does GERD worsen respiratory status in CF Ps?
What can be done to prevent GERD in CF Ps?
Acid into lungs - aspiration - can cause more infections.
Fundoplication procedure + change in chest physio position.
P presents with dyspepsia, reflux, early satiety & regurgitation. Diagnosis?
GORD
P presents with RUQ + umbilical deep pain (to back). Have raised serum amylase & raised blood glucose.
Diagnosis?
Pancreatitis
What is the difference between pancreatic sufficiency and insufficiency?
PS = pancreas working efficiently PI = pancreas not working efficiently - sticky mucus has built up and blocks the exocrine glands.
What is CFLD?
Cystic Fibrosis associated Liver Disease
How prevalent is CFLD in Ps with CF?
Common - about 1/3 develop - can be made worse by oestrogen (so in F after puberty).
What does CFLD do?
Causes general dysfunction of the liver. Can have hepatic steatosis (FLD), biliary cirrhosis (focal or multilobular) & neonatal cholestasis (rare - dec in bile flow).
What are ALT, AST & GGT
Liver enzymes in blood serum.
Is colorectal cancer more prevalent in CF Ps?
CF Ps are x5-x10 more likely to develop CRC - should have screening from 40+
What are surgery risks to CF Ps?
CF Ps = hyper metabolic - drugs need to be calculated differently. CF Ps can also have reduced lung function - riskier for GA.
How does CF affect P’s nutrition?
Less absorption -
- Pancreas, biliary + intestinal loss = dec absorption of fats - dec ADE&K absorption
- Gastric, pancreatic + intestinal loss = dec absorption of carbs
- Pancreatic + intestinal loss = dec protein absorption
If a P has terminal ileum removed / lack of IF - what cannot be absorbed?
B12
What determines whether a reaction will proceed?
Gibbs free energy - whether the reaction is endothermic or exothermic - if exothermic (GFE neg) - reaction can spontaneously occur.
Are catabolism and anabolism positive or negative energy?
Catabolism = negative free energy (exothermic) - breaking bonds Anabolism = positive free energy (endothermic) - making bonds
What does coupling of reactions with ATP allow?
Reactions to proceed that require an input of energy - taken from the breaking of ATP bonds.
What are the two methods of phosphorylation that make ATP?
Substrative level phosphorylation (glycolysis)
Oxidative phosphorylation (ETC)
What do cofactors do? Name two types
Help the enzyme function efficiently - metal ions and coenzymes (substrates & prosthetic groups)
What are coenzymes that are covalently bound to the enzyme called?
Prosthetic groups
Name 3 coenzymes involved in respiration
NAD, FAD & CoA
How many ATP are produced from oxidative phosphorylation of NADH & FADH
NADH - 2.5
FADH - 1.5
What does CoA do?
Transfers acetate between molecules
Name the four stages of respiration. Why is it divided into stages?
Glycolysis, Pyruvate Oxidation (Link Reaction), Citric Acid Cycle + ETC
Provides lots of control points to prevent overly rapid breakdown, excess heat loss & non-utilisation of ATP that is made.
What are the products of glycolysis?
4 ATP are made, 2 are used in stage 1 - so is a net gain of 2 ATP.
2 NADH are produced
2 Pyruvate are produced
What is glycolysis controlled by?
Kinases - which are inhibited by the products of the steps:
Hexokinase - inhibited by too much G6P
Phosphofructokinase - inhibited by too much ATP or citrate (activated by ADP & AMP high levels)
Pyruvate kinase - inhibited by high levels of pyruvate, ATP or CoA.
What is the link reaction? Is it reversible or irreversible?
What are the products from this reaction?
Carrier protein in mitochondrial membrane that undergoes oxidative decarboxylation via pyruvate dehydrogenase.
Is irreversible.
Pyruvate is converted to ACoA (controlled by pyruvate dehydrogenase)
Products: 2 ACoA, 2 CO2 + 2 NADH
What are the control points of Krebs cycle?
- Link reaction (pyruvate dehydrogenase)
- Entry of ACoA into cycle (citrate synthase)
- Isocitrate dehydrogenase
- Ketoglutarate dehydrogenase
Many of these enzymes are activated by Ca - therefore inc levels of Ca during exercise in muscles stimulates and drives Krebs.
Are all inhibited by high levels of ATP & NADH
What are the products from Krebs?
Each glucose molecule makes Krebs x2
Therefore -
- 6 NADH
- 2 ATP
- 2 FADH
- 1 CoA
- 2 CO2
How does the ETC work?
H released split into H+ and e-. Electrons move across - lose energy at each carrier - used to pump H+ into inter membrane space –> electrochemical gradient. H+ moves back via ATP synthase (chemiosmosis). In matrix - H+ + e- + O2 = H2O.
O2 is final electron acceptor
Regenerated coenzymes are used in Krebs.
What are the 3 pathways into the ETC? How does each work.?
Complex I, II & Coenzyme Q
Complex I - NADH release - forms QH2 - moves to Complex III. 4H+ pumped in.
Complex II - succinate - fumarate from Krebs releases FADH2 - releases e and forms QH2. No H+ pumped.
CoQ - NADH from glycolysis directly drives formation of QH2 via CoQ in inter membrane space without using a complex (uses G3P shuttle).
Which 2 methods allow NADH to be brought into mitochondria?
G3P shuttle
Malate-aspartate shuttle
What happens at Complex III in ETC?
Receives electrons from I, II & glycolysis - in doing so 4 H+ are pumped into the intermembrane space before passing to cytochrome C in the inter membrane space - uses Fe to transfer electrons from III to IV (Fe2+ <> Fe3+).
What happens at Complex IV in ETC?
Accepts donated electrons - and attaches to O2 molecules - then uses H+ from matrix to produce H2O whilst also pumping more H+ into inter membrane space.
Which complexes in the ETC pump H+ into inter membrane space?
I, III & IV
Which enzyme creates ATP in the ETC?
ATP synthase
What do uncoupling reagents do?
Where are they found in the body?
Allow transport of H+ back into matrix bypassing ATP synthase - allows energy to be released as heat. Found in thermogenin in brown adipose tissue.
Why do muscles hurt after exercise at times?
Due to build up of lactic acid. When O2 is short - anaerobic respiration takes place - just glycolysis - pyruvate –> Lactate (NAD) + CO2 + H2O.
How many ATP are produced by lactate production?
2
What can be used in place of ATP during strenuous exercise?
Creatinine phosphate
How are fatty acids utilised in respiration?
Are changed from FA to ACoA for entry into Krebs via β-oxidation,
How is mitochondrial DNA inherited
From the mother only - father the mitochondria are in the flagella of sperm.
Why do mitochondrial DNA suffer greatest exposure and damage?
Because they are close to the ETC = greatest exposure to ROS.
Mitochondrial DNA is also less effective at correction & repair
Happens x10 more than nuclear DNA.
Which diseases have mitochondrial DNA damage over time been associated with?
Alzheimers, Parkinsons & T2 diabetes
Name some ROS
O2-, HO-, O22-, H2O2 & HOCl
Why are mitochondrial diseases from birth rare?
Affect the ETC - most are incompatible with life.
What are the implications of mitochondrial disease?
Which cells are most affected?
Reduces the capacity of cells to produce ATP.
Affects neurons, skeletal muscle and β cells of pancreas the most.
What are the symptoms of mitochondrial disease?
Exercise intolerance
Muscle weakness
Also - HF, arrhythmias, dementia, blindness & seizures
What are the two ways that mitochondrial disease can occur?
Threshold effect - threshold of mutated mitochondrial via damage that you need for pathology
Genetic bottleneck effect - randomness of mitochondrial division during ovum formation - means some will have resultant pathology whilst others wont.
What are the 5 classifications of mitochondrial disease?
- Mitochondrial transport system defects
- Substrate utilisation defects
- Krebb’s cycle defects
- Oxidative phosphorylation coupling defects
- Oxidative phosphorylation defects
What is LHON?
Lebers Hereditary Optic Neuropathy
Single base change in Complex I (or similar in III) - leads to reduced transport to Ubiquinone - less ATP produced (although some still produced via succinate and glycolysis) - but not enough to support neuronal activity = damage to optic nerve - blindness
What is MERRF?
Myoclonus Epilepsy with Ragged-Red Fibre
Mutation in tRNA - disrupts synthesis of proteins needed for oxidative phosphorylation = skeletal fibres with abnormal shaped mitochondria (clump together).
What possible treatments are there for mitochondrial myopathies to prevent inheritance?
Replacing defective mitochondria in ovum - can merge DNA from 2 eggs - use IVF and transfer pronuclei of fertilised eggs to a zygote with normal mitochondria.
How do infections directly cause diarrhoea?
Cell death –> loss of absorptive area
+
Increase inflammatory response - causes fluid to leak into the bowel
How do infections indirectly cause diarrhoea?
Toxins (cytotoxic or pro inflammatory)
Mimic endogenous cell signalling mechanisms (act upon ion channels)
Form pores in cell membrane (cholera) or inc permeability at tight junctions
End result = fluid and electrolyte loss
Which medications can cause diarrhoea?
Metformin
ABs
Omeprazole
Ace Inhibitors
What are the main bacteria that cause diarrhoea?
Salmonella
Campylobacter
C. Diff
Cholera
What is the main virus that causes diarrhoea?
Norovirus
What are the causes of acute diarrhoea?
Infection - Viral, Bacterial
Meds
Parasites (unusual in UK)
Do you test for acute diarrhoea?
If P well - doesn’t usually need tests. Only test of symptoms persist and seems more chronic pathology.
What percentage of pop have diarrhoea?
7%
How do you define acute, persistent & chronic diarrhoea?
Acute = < 14 days Persistent = > 14 days Chronic = > 4 weeks
How do drugs cause diarrhoea?
Osmotically active
Affect ion absorption
Inc Transit time
Alter absorption (causing malabsorption of fluid)
ABs - can cause overgrowth –> bugs like C Diff
When should you investigate acute diarrhoea?
P is unwell Blood/pus in stool Recent ABs Recent hospital admission On PPI Recently been abroad Immunocompromised
Start with stool microscopy
What is in diarrhoea?
H20
Na
HCO3
K
What can bad diarrhoea affect?
Fluid and electrolyte levels
What can persistent diarrhoea cause?
Dehydration, hypokalaemia & acidosis (due to dehydration)
What is the treatment for acute diarrhoea?
Usually none if P remains well.
If unwell - fluids inc saline & glucose - reduces Na loss from proximal small bowel + improves water absorption via Na/Glu transporter.
V rare for ABs unless serious infection.
What is the commonest cause of chronic diarrhoea?
IBS
What defects of the colon can cause chronic diarrhoea?
Cancer
Diverticulitis
IBD
What defects of the SI cause chronic diarrhoea?
Coeliac disease IBD Lactose intolerance Bile salt malabsorption Short bowel / intestinal failure
What defects of pancreas cause chronic diarrhoea? What will it cause?
Exocrine failure
CF
Causes steatorrhea (not digesting fats)
What defects of endocrine system can cause chronic diarrhoea?
Hyperthyroidism
Addison’s
Hormone Secreting Tumours
Which parasites can cause chronic diarrhoea?
Threadworms
Name 4 mechanisms of diarrhoea
Osmotic - fluid is drawn into lumen (lactose intolerance, steatorrhea)
Secretory - fluid is secreted into lumen (infection, gut hormone excess, post radiation)
Failure of absorption (coeliac, short gut syndrome)
Mechanical narrowing - overflow diarrhoea (neoplasia, stricture)
What faecal analysis tests can you do for diarrhoea?
Stool microscopy - infection, parasites
Faecal calprotectin level
qFIT
Faecal elastase (pancreatic exocrine levels)
What blood tests can you do for chronic diarrhoea?
Thyroid FBC CRP tTG B12 Folic Acid & Folate Gut Hormones Minerals & Vitamin levels if worried about malabsorption
How can you examine the colon?
Colonoscopy
Virtual colonoscopy
Capsule colonoscopy
How can you examine the small intestine?
MRI
Capsule endoscopy
OGD
Colonoscopy for extreme end of bowel (can reach terminal ileum)
How does IBS present?
Abdo pain with possible painful defecation
+/- Altered stool frequency & appearance + 2 of:
- Altered stool passage
- Bloating/distension (worsened by eating)
- Rectal mucus
+ ALTERNATIVES EXCLUDED
Is mucus more common with IBS or BC?
IBS
How much of global pop have IBS? Which ppl is it most common in?
20% (probably underreported)
20-30 yr olds, F>M (underreporting?)
What is the cause of IBS?
Unknown - but possibly psychosocial influence, genetic link or infection link.
What is the management of IBS.
Rule out alternatives, reassure.
Dietary changes - avoid triggers - poss low FODMAP diet. Probiotics help.
Avoid stress
If symptoms persist = do tests and poss colonoscopy.
What are the medical treatments for IBS?
Diarrhoea - Loperamide (Immodium)
Buscopan (hydroscine butyl bromide) - antimuscarinic for cramps
Constipation - Laxatives (bulk-forming)
Tricyclic antidepressant - Amitriptyline (90% respond)
How does loperamide work? What are its SE?
Agonist for opioid receptors = anti motility. Opioid receptors in the bowel = mu receptors. When stimulated - inhibit GI motility and inc tone in sphincters. Loperamide only binds to SI mu receptors in the large intestine.
SE: Constipation, arrhythmia in high dose
How much of the pop has constipation?
1-2% - poss underreported. F>M.
What is the definition of constipation?
Less than 3 poos per week, excessive straining, abdominal pain / bloating. Look for change in intrinsic pattern and symptoms.
What are the functional causes of constipation?
IBS Behavioural Slow transit Pregnancy Diet (poor fluid +/- fibre)
What are the colonic causes of constipation?
Cancer
Extrinsic compression
IBD w/ stricture
What medications cause constipation?
Opioids
Loperamide
Iron tablets
What endocrine condition can cause constipation?
Hypothyroidism
What neurological conditions can cause constipation?
Parkinsons
MS
Hirschsprung’s disease
What acute pathology causes constipation?
Bowel obstruction
What is Hirschsprung’s disease?
Congenital absence of ganglia in the bowel –> failure of peristalsis.
90% diagnosed in infancy as baby doesn’t pass meconium.
What are the possible consequences of chronic constipation?
Haemorrhoids Anal fissures Painful defecation Rectal prolapse Abdo pain Bloating Diverticular disease Urinary retention Faecal impaction Overflow diarrhoea Stercoral perforation
What investigations should you do for constipation?
Bloods - thyroid, FBC, inflammatory markers
qFIT
Calprotectin
Acute - AXR, CT (rule out BO), colonoscopy, virtual colonoscopy
What is diverticular disease?
Protrusions of mucosal pouches through the bowel wall.
What is thought to cause diverticular disease?
Thought to be closely linked to constipation + poor dietary fibre.
Which part of the bowel has the highest incidence of diverticular disease?
Sigmoid colon (where the intra-luminal pressure is highest)
What are the symptoms of bowel obstruction?
Absolute constipation - no passage of stool or wind.
What are the causes of bowel obstruction?
Extrinsic compression (mass, adhesions, hernias)
Bowel wall problem (neoplasia, inflammation, stricturing)
Luminal blockage
What is the management of a bowel obstruction?
Resus (if needed) = CT to decide whether intervention needed.
How do bulk forming laxatives work? Give an example of one.
Attract fat and water into lumen - incs mass - causes distension - triggers enteric reflex - causes peristalsis. Also softens stool.
Eg. Ispaghula hulk
How do osmotic laxatives work? Give an example of one.
Draws water into the lumen of the bowel - inc faecal mass & softens - enteric reflex - peristalsis.
E.g. lactulose, phosphate enemas, Movicol, Moviprep
How do stimulant laxatives work? Give an example of one.
Stimulate bowel nerves for peristalsis + have osmotic agent - softer stool.
E.g. Senna
How do stool softeners work? Give an example of one.
Allows fat and water to penetrate the stool - makes easier passage & reduced straining.
E.g. Docusate sodium
What are 1st and 2nd line treatments for constipation?
1st = Ispaghula hulk
2nd = Docusate sodium
What are possible side effects of laxatives?
Electrolyte imbalances, diarrhoea, wind, bloating (bulk-forming & osmotic), cramps (osmotic & stimulant), bowel obstruction.
How do we treat constipation?
Suggest high fibre diet + inc fluid + laxatives. If it doesn’t resolve - further testing.
What is Coeliac Disease? Which genes cause it?
Gluten - broken into gliadin - causes inflammation of small intestine (enteropathy) - means surface cant effective absorb. Because villi are inflamed - they shorten and atrophy.
Caused by DQ2 & DQ8 genes.
What percentage of pop have coeliac?
1% - F>M.
What is gluten found in?
Wheat, barley, rye & possibly oats if contaminated
What are the symptoms of coeliac disease?
Diarrhoea, steatorrhea, weight loss, anaemia, abdominal pain, malabsorption.
Malabsorption -> anaemia -> glossitis (B12 def), mouth ulcers, dermatitis herpetiformis, pale eye, angular stomatitis & chelitis.
How does coeliac present histologically?
Decreased folds of the intestine, villous atrophy (smooth shiny surface) & scalloping of the folds. Can form lots of crypts with large presence of inflammatory cells (trying to stop gliadin crossing into bowel wall). Also increased intraepithelial lymphocytes.
Why does gliadin cause coeliac disease?
It crosses enterocytes & forms a complex with tTG - binding to T cells - causes them to produce antibodies - anti-tTG, anti-endomysial & anti-gliadin.
Why does coeliac disease cause dermatitis herpetiformis?
The tTG complex can react to epidermal TG causing the rash.
What are the three antibodies produced in response to tTG in coeliac Ps?
Anti-tTG
Anti-gliadin
Anti-endomysial
What is the gold standard investigation for coeliac disease?
Endoscopy biopsy (OGD).
What is the Marsh criteria?
For coeliac disease - 3 things observed:
Raised intraepithelial lymphocytes, crypt hyperplasia + villous atrophy
What is the treatment for coeliac disease?
Gluten free diet (oats ok) Vaccination against pneumococcus Screen for osteoporosis Supplements - iron, B12 & folate Screen for other AI disease & thyroid disease Annual FBC
Why are coeliac Ps vaccinated against pneumococcus?
Because for many the spleen becomes inept.
How does Crohn’s appear on histology?
Patchy, transmural ulceration - anywhere from mouth to anus. Inflammation is full depth - can form fistulae, ulcers & strictures. Granulomas can be seen. Perianal disease may also be seen.
Can spread to adjacent bowel & organs - can also cause localised abscesses.
Who is more likely to get Crohn’s?
Younger adults & children - bimodal peak at mid-20s and mid-60s.
Strong link to smoking
Higher in Western & Jewish Ps
What causes Crohn’s?
Not known - combo of genetic, immune, environment, diet, smoking & NSAIDs. Strong genetic link.
What happens to the mucosal barrier in Crohn’s?
Defects in the mucosal barrier allow pathogens and antigens to invade.
Which gene is most commonly identified in Crohn’s?
Chromosome 16, NOD2 - most common. 200+ others have also been identified.
What is the treatment for Crohn’s?
Acute - nil by mouth, IV ABs (if abscess) & HCS, liquid diet for 1 month (modulen).
Meds: Thiopurines, Biologics, Prednisolone
Surgically - 50% will need - of these 70% will need a second op within 5 years. Remove infected patches.
How does Ulcerative Colitis present?
Continuous inflammation, superficial to mucosa only (unlike Crohn’s), only affects colon. Lesions start at rectum and extend proximally with no breaks. Does not affect small intestine.
What does ulcerative colitis look like on histology?
No deep ulcers, continuous inflammation.
Crypt abscesses but no granulomas.
Affects only mucosal layer.
Which disease is more at risk for perforation and why - Crohn’s or UC?
UC - lumen can become so narrowed with inflammation that air cannot pass - causes toxic megacolon.
What is the risk of colectomy in Ps with UC?
20-30%
In UC - what are the following?
- Proctitis
- Left-sided disease
- Pancolitis
Proctitis = inflammation of rectum only
Left-sided disease = rectum and sigmoid colon only
Pancolitis = entire colon inflammation
What are the statistics regarding progress of UC?
First year - 1/3 remission, 1/3 symptomatic, 1/3 progressive to extensive disease.
What does extensive UC put Ps at risk of developing?
More flares, perforation and colorectal cancer.
What is the treatment for UC?
Acute - IV HCS, LMWH, Mesalazines, Thiopurines then Biologics. Use corticosteroids for flares in between.
What are mesalazines?
5-aminosalicyclic acids (5-ASAs) = are pH dependant capsules - can alter release timing along passage.
What is Barrett’s oesophagus?
Changes in the lining of oesophagus from squamous epithelium to columnar with goblet cells.
What is the progression of Barrett’s oesophagus?
GORD –> Reflux oesophagitis –> Metaplasia
What are the signs of Barrett’s oesophagus?
Dysphagia & heartburn
What is metaplasia?
Replacement of one adult cell type to another adult cell type.
What is dysplasia?
Increased cell numbers - can be low or high grade - is a pre-malignancy stage.
What is the biggest risk factor for oesophageal adenocarcinoma?
Barrett’s oesophagus
What is the pathogenesis of Barrett’s Associated Adenocarcinoma?
Normal squamous –> Reflux / Oesophagitis –> Metaplasia (Barrett’s) –> Low grade dysplasia –> High grade dysplasia –> Adenocarcinoma
What functions do secretions perform?
Lubrication
Digestion
Protection
What are the 3 major salivary glands, what percentage of saliva do they make and what does their saliva contain?
Parotid - 25% - serous + high conc salivary amylase
Submandibular - 70% - mixed mucous and serous.
Sublingual - 5% - mucus
What are dispersed salivary glands?
Smaller salivary glands found in the mucosa of mouth & tongue.
What are the components of saliva?
Water Electrolytes - Na, Cl, HCO3 & K Enzymes IgA Mucin Urea & Uric acid (waste for removal)
What does α-amylase in saliva do?
Hydrolyses α 1-4 glycosidic bonds in starch
What do lysozymes in saliva do?
Hydrolyses peptidoglycan in G-ve bacteria.
When is lingual lipase activated?
In low pHs - stomach acid.
What does lactoferrin in saliva do?
Antibacterial - chelates iron - stops microbes from multiplying.
What does IgA do in saliva?
Prevents microbial attachment to the epithelium.
What do myoepithelial cells around acinar cells do?
They contract and force more saliva from the acinar cells into the acinus & duct.
What are the two stages of saliva formation?
1) . NKCC1 co-transporter transports Na & Cl into the acinus - water follows - forms isotonic fluid.
2) . Fluid flows into the duct of the salivary gland - reabsorption of Na and Cl occurs, water cannot follow as ductal cells are relatively impermeable to water - K and HCO3 flow into the ductal fluid = hypotonic fluid.
What happens to the components of saliva when flow rate increases?
Becomes more isotonic - BUT is always slightly hypotonic - Na & Cl levels inc.
What is the pH of saliva?
6-7
How does the ANS control salivary secretions?
PSS - stimulates via CN7 (submandibular and sublingual) and CN9 (parotid) = inc saliva production and vasodilation.
SS - superior cervical ganglion & sympathetic postganglionic nerves - INHIBIT - vasoconstriction & reduced saliva = dry mouth (e.g. nervous)
Which cranial nerve innervates the submandibular and sublingual salivary glands?
CN 7 - Facial nerve
Which cranial nerve innervates the parotid salivary gland?
CN9 - GPG
Which AI disease destroys exocrine glands - leading to reduced tear and saliva production?
Which test is used to determine?
Sjorgren’s syndrome
Schirmer’s test (filter paper to eyes)
Which disease causes lack of adequate saliva leading to tooth decay & halitosis, difficulty speaking, dysphagia & bacterial overgrowth in the mouth?
Xerostonia
Where are gastric glands in the stomach? What do they contain?
In the mucosa.
Exocrine and endocrine glands
Which cell produces mucus?
Mucous neck cells
Which cell produces HCL in the stomach?
Parietal cells
Which cell produces intrinsic factor in the stomach?
Parietal cells
What is the function of HCL in the stomach?
It converts pepsinogen to pepsin.
Denatures proteins - allowing easier protein breakdown
Kills microbes
What is the function of Intrinsic factor?
Needed for B12 absorption in the SI - needed for erythropoiesis.
Absence of IF = pernicious anaemia.
Which cells produce pepsinogen?
Chief cells
Which cells produce gastric lipase?
Chief cells
Which cells produce rennin?
Chief cells
What does pepsinogen do?
Used to break down proteins (activated in the presence of HCL and covered to pepsin).
What does gastric lipase do?
Breaks down 3Gs to FAs and 2Gs.
Name 3 exocrine glands in the stomach.
Mucous neck cells
Parietal cells
Chief cells
Name 3 endocrine cells in the stomach
G-cells
D-cells
ECL cells
Which cell in the stomach can be endocrine or paracrine.
D cells
Which cells in the stomach produce gastrin?
G cells
In what 3 ways are G cells in the stomach stimulated?
CNX
Distension of the stomach
Presence of peptides
What does gastrin do?
Activates parietal and chief cells.
Causes lower oesophageal sphincter contraction
Increases motility of the stomach
Which cells produce somatostatin?
D Cells
When is somatostatin produced?
What does it do?
When the H+ levels in the duodenum are too high.
It inhibits H2 receptors on parietal cells - prevents H+ release into the stomach.
Which cells produce histamine in the stomach?
The enterochromaffin-like cells
What is the membrane of parietal cells like?
Branched canaliculi with lots of villi
In which 3 ways can parietal cells be stimulated?
1) . CNX (via ACh)
2) . Gastrin from blood stream - binds to their basolateral membrane.
3) . Histamine binds to H2 receptors and stimulates.
What happens inside parietal cells when they are stimulated?
ACh/Gastrin simulate and activate PLC - releases Ca2+ or histamine –> H2 receptor –> AC –> cAMP –> PKA.