Gastroenterology Flashcards
Describe the anatomy of the oesophagus including: vertebral levels, muscular types, and epithelial cell types
Oesophagus starts at C5 (where the trachea begins and ends at T11 the fundus of the stomach
Upper oesophageal sphincter is between pharynx and oesophagus, Lower oesophageal is at T11
Upper 1/3/ cervical oesophagus which ends at the sternal notch has skeletal muscle and sqaumous epithelial
middle 1/3 thoracic oesophagus is from trachea to diaphragm. Has an upper middle and lower part. the upper and middle have a mixture of skeletal and smooth muscle, the lower is only smooth muscle with columnar epithelial
Describe the phases involved in swallowing
Stage 0= oral, chew to make bolus the sphincters are closed
Stage 1= pharangeal phase, UOS opens as a reflex, LOS opens by vasovagal reflex/receptive relaxation
Stage 2= Upper Oesophageal phase, UOS closes, the superior circular muscle contracts and inferior relaxes, sequential contraction of longitudinal muscle to push bolus down
Stage 3- Lower Oeophageal Phase, LOS closes when bolus moves thru
What test determines oepophageal motility
Manometry: measures pressure
the peristaltic waves should be 40mmHg
LOS resting pressure 20 mmHg and then 15mmHg when in receptive relaxation
What neurotransmitter mediates the relaxation of the LOS
inhibitory noncholinergic nonadrenergic neurones of the myenteric plexus
What are the terms that mean (1) difficulty in swallowing and (2) pain on swallowing
(1) Dysphagia : need to know if occurs for solid, liquid, is intermittent or progressive, precise or vague
(2) Odynophagia
Define regurgitation and reflux
Regurg: return of oesophageal contents from above and obstruction
Reflux: passive return of gastroduodenal contents to the mouth
What are the functional disorders of the oesophagus
Absence of a stricture can be caused by two things
1)Abnormal oesophageal contraction
Hypermotility, Hypomotility and Disordered coordination
What is hypermotility in the oesophagus named
Achalasia (LOS doesnt relax)
What causes achalasia (pathophysiology and cause)
Loss of ganglion cells in Aurebach’s myenteric plexus on LOS wall, decreased inhibitory NCNA neurones. This causes increased resting pressure of LOS so receptive relaxation is too late and too weak. The pressure in LOS is much higher than stomach. This causes food to collect in oesophagus causing pressure and dilation of the rest of the oesophagus which stops peristaltic wave propagation
Primary: aetiology unknown
Secondary: due to diseases causing oeophageal motor abnormalities
What diseases can cause secondary achalasia
Chagas disease
Protazoa infection
Amyloid/sarcoma/eosinophilic oesophagitis
Describe how achalasia will present
weight loss, Odynophagia, insidious onset- have symptoms for ages and if not treated oeophagus keeps dilated
leads to pneumonia or esophagitis
What does achalasia put patients at risk of
Oeophageal cancer
How is achalasia treated and what are the risks
Pneumatic Dilation: Balloon inflated the LOS to weaken and stretch circumferentially, decreases pressure so food can pass
Surgery : Heller’s myotomy whch takes away muscle from above and below sphincter and then Dor fundoplication which folds the anterior fundus over. Risk of oesophageal and gastric perforation, cutting vagus nerve, injuring spleen
What is the term for hypomotility
Scleroderma
What is the cause of scleroderma (pathophysiology and causes)
neuronal defects causes atrophy of the oesophagus’ smooth muscle, peristalsis in the distal portion ceases causing hypomotility. Lower resting pressure in LOS, leads to development of gastroesophageal reflux disease,
What syndrome is associated with GORD
CREST syndrome
calcium deposits, spasm of blood vessels in response to cold or stress, acid reflux, sclerodactyl- thickening of skin on hands, dilation of capillaries
How is scleroderma treated
Check its not an organic obstruction
Prokinetiks like cisapride to improve peristalsis force
if peristalsis has failed usually reversible
Give an example of disordered coordination problems of the oesophagus
corkscrew oesophagus
Describe corkscrew oesophagus
Oesophageal spasm, incoordinate contractions so get dysphagia and chest pain. Pressures from 400-500mmHg. Hypertrophy of circular muscle and see the corkscrew on barium test
How is corkscrew oesophagus treated
Pneumatic dilation may result in a response
What is oesophageal perforation, where its most likely to happen and the causes
Hole in the oesophagus
happens at the three areas of anatomical constriction- the cricopharyngeal constriction, aortic and bronchial constriction, diaphragmatic and sphincter constriction.
It can also be due to cancer, foreign bodies, physiological dysfunction
Causes: OGD procedures (endoscope perforates Killians dehisense which is between the pharynx’s inferior constrictor muscles and the cricopharyngeal muscle) ,Boerhaave’s is spontaneous, foreign bodies, trauma,
What is Boerhaave’s and identify the most common findings/sign
Drinking a lot causes repeated vomiting againsta closed glottis creating sudden increased intra-oesophageal pressure with negative intrathoracic pressure. Creates perforation at the left posterolateral aspect of the distal oesophagus which is the weakest point
vomiting and chest pain are the signs
Describe how foreign bodies and trauma to the oesophagus causes oesophageal perforation, name the symptoms
Foreign bodies- disk batteries can erode and make large holes, magnets, sharp objects, acid/alkali things like drain cleaner burns the oesophagus
Trauma - if neck trauma usually penetrative force, if thorax then blunt force
dysphagia, chest pain, and shortness of breath, blood in saliva
How does oesophageal perforation present
Pain, fever, dyspahgia, emphysema
What investigations should be carried out for oesophageal perforation
Chest X ray, CT scan, swallow test, OGD
look for outline of mediasteinum = air in cavity/pneumomediasteinum
look for air or fluid leaking out
How is oesophageal perforations managed
is a surgical emergency so nil by mouth, IV fluids, broad spectrum ABs and antifungals as lots in the oesophagus . take bloods, tertiary referral centre
conservative management= covered metal stent
operative management is default- primary repair or oesophagectomy
How does the stomach protect against reflux and failure of these mechanisms results in what
LOS usually the barrier against reflux (pepsin and HCl)
3 protective mechanisms:
oesophageal peristalsis reflex, clears volume
saliva pH clearance
epitheliums barrier properties
Failure of protective reflux mechanisms
Gastro-oesophageal refluc Disease GORD
What inhibits and promotes reflux
INHIBITS: Acetylcholine, alpha-adrenergic agonists, hormones, protein rich food, histamine, high intra abdominal pressure all increase LOS pressure and inhibit reflux
PROMOTES: VIP, beta-adrenergic agonists, hormones, dopamine, NO, PGI2, PGE2, chocolate, acid gastric juice, fat, smoking all reduce LOS pressure promoting reflux
What causes normal sporadic reflux
pressure on full stomach, swallowing (as the oesophageal pressure and pH rises after swallowing as saliva is neutral) and sphincter opening transiently (creating low LOS pressure momentarily) are normal
Failure of protective mechanisms results in what, explain
GORD
If there is decreased sphincter pressure
If there is more transient sphincter opening theres more air and CO2 entering,
Hiatus hernia: (1) sliding hiatus hernia where stomach moves through diaphragm which moves the gastrooesophageal junction/ LOS, (2)rolling/paraoesophageal hiatus hernia where portion of stomach is herniates thru diaphragm
Abnormal peristalsis causes lower volume clearance
Reduced saliva production during sleep can reduce pH clearance, smoking can also reduce the buffering capacity of saliva and reduce pH clearance
Defective epithelium mucosal due to alcohol
All of these lead to GORD which can reult in reflux oesophagitis where the lining is damaged and lead to carcinoma
How is GORD investigated and treated
Investigations: Oesophagealgastro duodenoscopy (OGD), oesophagel manometry, 24h oesophageal pH recording
Treat: lifestyle changes (weight loss, smoking ess alcohol) and Proton Pump Inhibitors
Dilation of peptic strictures, Laparoscopic Nissen’s fundoplication
What is the function of the stomahc
Break food into smaller particles through acid and pepsin.
Releases food in a controlled and steady rate
Kills parasites and bacteria
Describe what substances/molecules are found in different regions f the stomach
In the cardia and pyloric regions (top and bottom valve parts) its only mucus
Body and fundus have parietal and chief cells to make acid : mucus, HCl, pepsinogen
Antrum: gastrin
What types of gastritis are there
1) Erosive and haemorrhagic gastritis: causes and acute ulcer so bleeding and perforation. Causes of this can be NSAIDs, alcohol, multi-organ failure, burns, trauma and ischamia
2) Nonerosive, chronic active gastritis: helicobacter pylori acts on antrum to increase gastrin so acid secretio is increased resulting in a gastral and duodenal ulcer
3)Atrophicgastritis: Autoantibodies act on the parietal cells in the fundus, kparietal cells atrophy so less pepsinogen, intrinsic factors and acid secretion. (More acid secretion need means G-cell and Enterocromaffin like-cells hyperplasia which can lead to epithelial metaplasia and carcinoma. Less intrinsic factors means vitamin B12 cannot be absorbed so get pernicious anaemia)
All three can lead to :
Reactive gastritis which results in epithelial metaplasia and carcinoma
Describe the regulation of gastric secretion: both the stimulation and inhibition
Stimulation:
ACh acts on M1 receptors of vagal parasymapthetic fibres: stimulates acid secretion, G cells secrete gastrin and enterochromaffin cells which release histamine
Gastrin from the antrums G cells (makes partietal cells make H+/K+ pump work and chief cells to make pepsinogen to pepsin
Histamine (enterochromaffin like cells and mast cells) binds to H2 receptors, parietal cells will make HCl
Inhibition:
Secretin : inhibits antral G cells so no gastrin (less activation of parietal and chief cells)
Somatostatin: inhibits histamine release, and the H+/K+ATPase that parietal cells need
Prostaglandins PGs (E2 and I2), TGF-alpha and adenosine
How is the stomach protected from ulcer formation
1) Mucus film protects from pepsin and H+
2) HCO3 secretion from surface epithelium maintains a pH gradient, and if bicarbonate meets a proton will make water and Co2 (prostaglandins stimulate HCO3/ NSAIDs like ibuprofen inhibits this effect- so take NSAIDs with acid suppressant)
3)Epithelial barrier: EGF from salivary glands stops H+
4) Mucosal blood perfusion: Blood flow contributes to protection by supplying the mucosa with oxygen and HCO3-, and by removing H+ and toxic agents diffusing from the lumen into the mucosa.
If there is damage to the epithelium how does the body repair itself, explain the two phases
Migration: adjacent epithelial cells flatten and slide across the basement membrane to close the gap
Cell Growth to close the gap stimulated by EGF, TGF-alpha, IGF-1, GRP and gastrin
Describe acute wound healing
Acute Wound Healing: basement membrane destroyed in wounds so attract leukocytes and macrophages to phagocytose the necrotic cells, promote angiogenesis and regenerate ECM after repairing basement membrane. Epithelial cells then close by restitiution/migration and cell division
What causes ulcer formation
Helicobacter pylori disturbs the barrier function
NSAIDs (ibuprofen and aspirin) or smoking reduces prostoglandin synthesis so less inhibiton of HCl or pepsin so get too much gastric acid which is chemical aggression
Lower HCO3- secretion
Decreased cell fromation
Decreased blood perfusion to take protons away due and mucosal protection decreases
How are ulcers of the stomach treated
Medical: Proton pump ingibitor or H2 blocker, if CLO test shows its due to H.pylori then triple AB’s (amoxiccilin, clarithromycin, pantoprazole) for 1-2 weeks
Surgical:
if ulcer doesnt heal in 12 weeks then observe for another 12. Check serum gastrin and then do OGD and biopsy the four quadrants of the ulcer if it is refractory (non healing)
After surgery then may need continuous NSAIDs, complications of surgery are haemorrhage, obstruction and perforation.
If gastrin levels are high after 24 weeks what two diagnoses are possible
g cell hyperplasia or gastrinoma Zollinger-Ellison Syndrome (tumour secreting gastrin which causes lots of ulcers)
What three factors control thirst
Osmolality (conc)
Blood volume reduced
Blood pressure reduced
What hormone regulates osmolality, how does it work and where
ADH/Vasopressin
is stored in the posterior pituitary and when released binds to the V2 receptor on the kidneys collecting duct to insert aquaporin 2 channels. When ADH is high in the plasma it means anti diuresis is achieved and small amounts of urine passed. Also binds to the V1 receptor to cause constriction
In which regions of the hypothalamus are osmoreceptors located
Organus vasculosum of the lamina terminalis / circumventricular organs
Subfornical Organ
Describe the process of ADH release
Osmoreceptors in the organus vasculosum of the lamina terminalis and the subfornical organ. When plasma is more concentrated/ high osmolality, water moves out the osmoreceptors and they shrink. Shrinking means the membrane: cation channels increases so more activation and the membrane depolarises. A positive charge therefore moves across the osmoreceptor and fires and action potential which triggers supraoptic magnocellular nuceli which stimulates ADH producing cells in the posterior pititary to increase ADH. ADH is released, fluid retention occurs through ADH binding to V2 receptors and inserting aquaporin 2 channels, and thirst is triggered
How is relief of thirst sensation caused
Receptors in the mouth, pharynx and oesophagus decrease thirst sensation even before sufficient water has been absorbed- this is short lived but to ensure not too much is drunk
Completely relieved when plasma osmolality is decreased or blood volume/ arterial pressure decreased
Describe how the body responds to changes in blood pressure/volume
When blood pressure/volume drops then juxtaglomerular cells of the renal afferent arteriole release renin. Renin breaks down angiotensinogen that the liver produces into angiotensin I. Angiotensin I is then broken down to angiotensin II by ACE. Angiotensin II then increases sympathetic activtiy and causes vasoconstriction, causes ADH secretion, stimulates thirst and stimulates the zona glomerulosa of the adrenal cortex to release aldosterone which will then absorb Na+ and Cl- and excrete K+
How is body weight homeostasis achieved
Reduction of adipose tissue increases food intake and reduces energy expenditure and reduces sympathetic nervous system activity
Increase does the opposite
What are the terms meaning appetite stimulant and appetite suppressant respectively
Stim- Orexigenic
Supp- Anorectic
What nucleus in the brain regulates food intake
Arcuate nucleus
How is appetite regulated
(1) Leptin (2) Ghrelin, PYY and gut hormones (3) neural input all give infromation to the hypothalamus. The arcuate nucleus of the hypothalamus has an incomplete BBB so allows access to these peripheral hormones, when ghrelin is produced due to an empty stomach it stimulayes synthesises info producing either appetite stimulant/orexigenic neuropeptides such as NPY and AGRP. When PYY and other gut hormones like GLP-1 and CCK are relasease from a full stomach the arcuate nucleus produces suppressive/anorectic neuropeptides such as POMC (in PYY’s case it will also inhibit NPY) . It sends this info to the paraventricular nucleus that has neurones that terminate in the posterior pituitary.
Leptin is in proportion to adipose tissue in the body, If it is high it signals to stop eating and burn fat
Describe the difference between the two orexigenic neuropeptides
AGRP inhibits POMC to encourage eating (inhibits the inhibitor double negative)
NPY directly stimulates
How does the neuropeptide that stimulates a decrease in food intake work. What is this system called
Melanocortin system
POMC triggers neuropeptides such as alpha-MSH which act on the paraventricular nucleuses MC4R receptor to decrease food intake. However AGRP which inhibits POMC has to be inhibited for POMC to be activated
What mutations of the CNS could possibly affect appetite
POMC deficiency and MC4-R deficiency
Signals from amygdala: emotion, memory, reward
Other parts of the hypothalamus
Problems with the vagus nerve to the brain stem
What is the hormone produced by fat and what does it do, give an example of one
Adipostat, hypothalamus senses the concentration and alters the neuropeptides adjustingly
Leptin is an example, is made in white adipose tissue and enterocytes, circulates in plasma and acts on hypothalamus to regulate appetite and energy expenditure. Leptin is in direct proportion to amount of body fat. If it is high it decreases food intake and increases thermogenesis/energy expenditure
What mechanisms can affect leptins effect on fat regulation
Congenital leptin deficiency : absent leptin
Decreased leptin expression/secretion from adipose tissue : cant regulate
Leptin resistance
What gastrointestinal hormones control appetite and food intake, where are they produced and how do they work
Enteroendocrine cells in the stomach pancreas and small bowel secrete gastrointestinal hormones
ghrelin stimulates appetite when stomach is empty. Increases gastric motility and acid secretion. Directly modulates arcuate nucleus to stimulate ARGP and NPY peptides whilst inhibiting POMC neurones. Regulates reward, taste sensation, memory and circadian rhythm. LEvels spike before a meal
Peptide tyrosine tyrosine (PYY) inhibits food intake when stomach distended. Reelased in the terminal ileum and colon once feeded, Inhibits NPY release, stimulates POMC neurones to reduce appetite
What are some concequences of obesity
Sleep apnoea
Depression
Bowel cancer
Osteoarthritis
Gout
Stroke
MI
HYpertension
Diabetes
What is Rigler’s sign
Double wall sign, sign of pneumoperitoneum (free intraperitoneal air)
What are the signs of duodenal perforation
Riglers sign, subdiaphragmatic air , pain, vomiting, pyrexia
How are duodenal perforations managed
I.V fluids and AB’s
Surgery: laproscopic omental pathc
What are the clinical signs of pancreatitis
Amyalse levels high, pyrexial, epigastic pain, vomiting, fatty foods aggravate
How is pancreatitis investigated and managed
Fluids and painkillers, avoid fatty foods
US to see gallstones, if gallstones present then MRCP ( if gallstones may see dilated cyctic duct and a stricture below due to the stone)
Describe the embryology of the digestive tube and how this affects blood supply
Distal oesophagus to proximal part of of 2/3 of duodenum is foregut. The blood supply to this region is the coeliac trunk
Distal half of 2/3 of duodenum to proximal 2/3 of transverse colon is midgut. Blood from Superior mesenteric artery
Dital 1/3 of transverse colon to rectum is hindgut. Blood from inferior mesenteric artery
Which organs and issues are associated with colicky pain, and which constant
Colicky :
Ureter stones
Kidney stones
Cholelithiasis (stone in gallbladder)
Choledocholithiasis (in common bile duct)
Colon
Constant: kidney, spleen, liver problems
Describe radiation of pain of the upper six quadrants and what organ theyre associated with
Right hypochondriac : gallbladder radiates through the back and to the right
Epigastric : stomach, duodenum, pancreas: straight through to back
Left hypochondriac: pancreas: through back to righ
Right Lumbar and Left Lumbar: kidneys radiate from loin to groin
Umbilicus doesnt usually radiate
How would appendicitis present
Central epigastric pain then shifts to right iliac region.
Gradual onset
Constant pain
No radiation of pain
nausea, anorexia, fever
worse on movement
dull ache
How would bowel obstruction present
Central/epigastric pain
gradual
colicky
vomiting if bowels not open
Farting relieves pain
Moderate pain
How would uriteric colic present
Loin pain that radiates to groin
sudden onset
Colicky
vomiting
severe pain
How would cholelithiasis or choledocholithiasis present
Right upper quadrant that radiates to right shoulder
sudden onset
colicky
nausea and indigestion
after eating and fatty foods make worse
Since the GI tract has such a high antigen load what immunological state is it in
Restrained activation state as has to tolerate the resident microbiota, dietary ntigens but also respond to pathogens
What four major phyla of bacteria live in the gut microbiota
Bacteroidetes
Firmicutes
Actinobacteria
Proteobacteria
descirbe what symbionts, commensals and pathobionts are
Symbionts - bacteria that live in bowel and dont harm
Commensals- get an advantage from the host such as nutrients in bowel
Pathobionts- no advantage or harm but if become too much can lead to harm