Gastroentology Flashcards
Which of the following cranial nerves innervate the taste buds at the back of the throat (epiglottis)?
a) Cranial nerve VII
b) Cranial nerve IX
c) Cranial nerve X
d) Cranial nerve XII
e) Cranial nerve I
c) Cranial nerve X
aka Vagus nerve (taste epiglottis, back of the throat)
Largest immune organ
Gut
Which of the following processes associated with swallowing are under autonomic control?
a) Oral phase
b) Pharyngeal phase
c) Mastication
d) Bolus formation
b) Pharyngeal phase
Explanation:
- During this phase swallowing is normally involuntary.
- Impulses from pharyngeal sensory receptors travel to the brainstem swallow centre to initiate a series of involuntary pharyngeal muscle contractions.
- Soft palate elevates and palatopharyngeal folds appose and close the nasopharynx. Larynx elevates, vocal cords appose and epiglottis becomes horizontal, leading to closure of the trachea.
- Respiration is inhibited.
During the pharyngeal phase of swallowing:
- What causes closure of the naso-pharynx?
- What occludes the respiratory tract?
- Soft palate elevates and palatopharyngeal folds appose and close the nasopharynx.
- Larynx elevates, vocal cords appose and epiglottis becomes horizontal, leading to closure of the trachea.
Oesophogeal dysphagia
Difficulty in swallowing caused by failure of smooth muscle fibres to relax, which can cause the LOS to remain closed and fail to open
Oropharyngeal dysphagia
Difficulty in preparing and transporting food bolus through the oral cavity or initiating the swallow.
Arises from abnormalities of the muscles, nerves or structures of the oral cavity, pharynx and upper oesophageal sphincter.
Purpose of Gut Motility (4)
- Move food through the tube (peristalsis, colonic mass movements);
- Mix the food with secretions (grinding/trituration and segmentation),
- Migrating Motor Complex – fasting.
- Keep food in place – sphincters.
Which of the following are NOT functions of saliva?
a) Lubrication
b) Facilitates taste
c) Facilitates speech
d) Begins chemical digestion of peptides
e) Begins chemical digestion of lipids
f) Begins chemical digestion of carbohydrates
g) Stimulates mucosal repair and re-growth
h) Targets oral bacteria
d) Begins chemical digestion of peptides
List consequences of xerostomia (5)
- Tooth decay
- Oesophogeal erosions
- Difficulty swallowing food (poor nutrition)
- Difficulty with speech
- Opportunistic infection (candida albicans)
In HCl secretion from parietal cells, what does ‘G’; ‘H’ and ‘A’ stand for in relation to the hormones involved?
And what does GRP stand for?
Gastrin
Histamine
Acetylcholine (from parasympathetic nervous system)
Gastrin-releasing peptide
What is the primary ionic component of gastric acid:
1) At rest
2) When stimulated by food
1) NaCl (at rest)
2) HCl (when stimulated, by food)
When stimulated parietal cells
a) Change morphology
b) Secrete pepsinogen
c) Secrete somatostatin
d) Apically secrete HCO3-.
e) Secrete NaCl
a) Change morphology
Explanation:
Change is accommodating the release of gastric acids.
Cytoskeletal rearrangement and fusion of tubulovesicular vesicles into canalicular membrane. Greatly increases both surface area of apical membrane (5-10 fold) of parietal cell as well as number of H+/K+ pumps, K+ and Cl- channels.
Name the 3 phases of Gastric Secretion
Cephalic
Gastric
Intestinal
Cephalic Phase of Gastric Secretion
The smell, sight, taste, thought, and swallowing of food initiate the cephalic phase, which is primarily mediated by the vagus nerve
Gastric Phase of Gastric Secretion
Gastric: the food distends the gastric mucosa, which activates a vagovagal reflex as well as local ENS reflexes.
Partially digested proteins stimulate antral G cells.
Intestinal Phase of Gastric Secretion
Intestinal:
- AAs and peptides in the proximal small intestine stimulates acid secretion by stimulating duodenal G cells to secrete gastrin.
- Peptones stimulate an unknown endocrine cell to release an additional humoral signal that has been referred to as entero-oxyntin.
- AAs absorbed by the proximal part of the small intestine stimulate acid secretion.
Expression of what in the distal ileum facilitates recycling of bile acids to the liver?
a) Na+-taurocholate co-transporting polypeptide (NTCP)
b) Organic anion transporting proteins (OATPs)
c) Bile salt export pump (BSEP)
d) Apical sodium-dependent bile transporter (ASBT)
b) Organic anion transporting proteins (OATPs)
Bile acids
a) Chemically breakdown dietary lipids
b) Increase the efficiency of absorption of vitamins A, D, E and K.
c) Digest fatty acids.
d) Inhibit lipid diffusion in the duodenal contents.
e) Stimulate secretion of micelles.
b) Increase the efficiency of absorption of vitamins A, D, E and K.
Secretory diarrhoea - cause and effect
Caused by increased Cl- secretion. Water follows leading to fluid loss.
Osmotic diarrhoea - cause and effect
- caused by enterotoxins
- results in osmotic movement of water into the gut lumen
Regarding nutrient digestion and absorption, select the CORRECT answer.
a) Gastric amylase begins breakdown of carbohydrates in the stomach.
b) Lingual lipase is secreted by duodenal enterocytes.
c) Proteins must be broken down into monomers in order to be absorbed.
d) The majority of digestive enzymes are secreted from duodenal crypts.
e) Absorption of carbohydrate monomers is dependent upon brush border hydrolases.
e) Absorption of carbohydrate monomers is dependent upon brush border hydrolases.
Dietary disaccharides and breakdown products of larger carbohydrates are further digested by brush border hydrolases: Sucrase, isomaltase, glucoamylase, lactase.
Lactose intolerance - symptoms and cause
- diarrhoea, intestinal cramps and flatus
- Lactose-rich foods are poorly absorbed and remain in the intestinal lumen
Identify the site of action of a) pepsin; b) trypsin; c) peptidases in the digestion of proteins.
a) Pepsin - activated from pepsinogen in stomach
b) Trypsin - pancreatic enzyme active in lumen of duodenum
c) Peptidases - brush border (bound to enterocyte membranes and intracellular hydrolysis)
Arrival of fatty acids in the duodenum stimulate I cells to secrete
a) Cholecystokinin
b) Secretin
c) Acetylcholine
d) Gastrin
e) Somatostatin
f) Lipase
g) Colipase
h) Enterokinase
a) Cholecystokinin
Mixing of ingested nutrients with pancreatic, biliary and intestinal secretions is achieved by
a) Trituration
b) Intestinal peristalsis
c) Migrating motor complex
d) Segmentation
e) Mass movements
d) Segmentation
List 3 functions of the liver (8)
- Excretion - bile
- Metabolic energy
- Synthesise proteins
- Blood sink
- Detoxify
- Energy store
- Store for vitamins and minerals
- Immune functions (kupffer cells)
Which of the following statements regarding ketones is NOT correct?
a) Ketones are produced from lipids when glucose levels are low
b) Ketones are formed from Acetyl CoA
c) High ketone concentrations are a hallmark of obesity
d) Ketones are synthesised in the liver
e) Lack of thiophorase in the liver means that ketones cannot be used as an energy source by hepatic tissue.
f) Ketones are predominantly used in the central nervous system when needed.
c) High ketone concentrations are a hallmark of obesity
Components of Upper GI tract (4)
Oral cavity
Oesophagus
Stomach
Duodenum
Components of Lower GI tract (5)
Small intestine (jejunum and ileum)
Caecum / appendix
Colon
Rectum
Anus
Mastication
Chewing
Deglutination
Swallowing
3 functions of chewing
- Mix food with saliva (lubrication)
- Physically grinds up food to facilitate swallowing (importance of dentition)
- Begins chemical digestion (salivary amylase, lingual lipase)
Involuntary and voluntary of chewing
Involuntary: sensory reflexes initiated by food in the mouth are relayed from mechanoreceptors to the brain stem
Voluntary: chewing can override involuntary or reflex chewing at any time
How many pairs of muscles are involved in swallowing?
25 pairs of muscles in the mouth, upper airway and oesophagus
What are the 3 phases of swallowing? State whether each phase is voluntary or involuntary.
Oral phase - voluntary
Pharyngeal phase - involuntary
Oesophageal phase - involuntary
Meinteric Plexus controls…
motility
Achalasia
lower oesophageal sphincter fails to relax during swallowing
Dysfunction of myenteric plexus leads to:
failure to stimulate receptive relaxation & oesophageal stasis
oesophageal stasis
hours instead of seconds for food to pass
Major risk factor for swallowing disorders
Ageing
Disorders of swallowing (8)
- Nerve damage
- Poliomyelitis or encephalitis - may damage the swallowing centre in the brain stem – cause dysfunction of swallowing.
- Muscular Dystrophy
- Myasthenia gravis / botulism
- Deep anaesthesia - paralysis of the swallowing mechanism.
-Consequence of nervous system disorders e.g.stroke / brain tumours / cerebral palsy / dementia / ALS / MS / Parkinson’s disease
- Consequence of muscle disorders e.g. achalasia, cricopharyngeal spasms, oesophageal spasms, muscular dystrophy, myasthenia gravis, myositis, scleroderma
- Narrowing /blockages /structural issues e.g. tumours, eosinophilic oesophagitis, oesphageal diverticulum, oesphageal webs, GORD
Consequences of partial or total paralysis of swallowing (4)
- Dysphagia / aphagia
- Complete abrogation of the swallowing act
- Failure of the glottis to close (food passes into the lungs instead of the oesophagus – risk of pneumonia)
- Failure of the soft palate and uvula to close the posterior nares (food refluxes into the nose during swallowing)
GORD / GERD
Sphincter not fully functional
Food moves out of stomach, back into oesophageal space (LOS opens inappropriately)
Symptoms of GORD (3)
heartburn, cough, sore throat.
Result of repetitive reflux of acid into oesophagus (3)
- oesophageal stricture
- Barret’s oesophagus
- development of oesophageal adenocarcinoma
Oesophageal stricture
Narrowing of oesophagus
Barret’s oesophagus
Replacement of the oesophageal stratified squamous epithelium with columnar cells that are more similar to the gastric mucosa.
Hiatial Hernia
upward protrusion of the stomach through the diaphragm
risk for GORD
Common causes of GI obstruction (4)
- Cancerous growth
- Fibrotic constriction resulting from ulceration or peritoneal adhesions
- Spasm of a gut segment
- Paralysis of a gut segment
What causes dehydration as a result of a GI obstruction?
Large amounts of water and electrolytes lost
Pyloric obstruction may lead to…?
persistent vomiting
Obstruction in distral colon first leads to… which then leads to … ?
This has what effect on the large intestine?
constipation
vomiting
dehydration/rupture of LI
Name 3 types of oesophageal obstructions
Barrett’s oesophagus
Oesophagitis
Oesophageal tumuors
Gastritis
inflammation (bacterial infection) of the gastric mucosa leading to atrophy (wasting/thinning of tissue)
What drugs/chemicals damage the mucosa leading to gastritis?
Aspirin
Alcohol
Name the gastric secretory, motor and endocrine functions of the stomach
Secretory: HCl, HCO3 at rest, mucus
Motor: mixing and grinding/trituration
Endocrine: gastrin & somatostatin
Loss of gastric secretions can cause: (2)
Hypochlorhydria / Achlorhydria
Pernicious anaemia
What causes a peptic ulcer? (5)
- High acid and pepsin content
- Iriitation
- Poor blood supply
- Poor secretion of mucus
- Infection (H.pylori)
Primary cause of a peptic ulcer
Gastric juice
Where is the most common location of a peptic ulcer?
near the pyloric sphincter
What is a peptic ulcer?
Excoriated area of stomach or intestinal mucosa
Excoriated = removal of layer of intestinal muscoa
Coagulopathies
Bloods ability to form clots is impaired
Does a higher or lower gastric pH leads to pneumonia?
higher the gastric pH, the greater the risk of pneumonia
What increases a patient’s risk of haemorrhage from gastric stress ulcers? (2)
ICU patients who are mechanically ventilated or have coagulopathies
Gastrinoma / Zollinger-Ellison Syndrome
gastric ulcers due to very high rates of gastric acid secretion
Gastroparesis
Delayed gastric emptying
area postrema
vomiting centre of brain
Antiperistalsis
prelude to vomiting
What action initiates the act of vomiting?
Distention of the duodenum
How does retching work in a way that is different to vomiting?
- upper oesophageal sphincter remains closed
- because the lower oesophageal sphincter is open, the gastric contents return to the stomach when the retch is over
Nausea - meaning and cause
Conscious recognition of subconscious excitation in an area of the medulla closely associated with the vomiting centre
Caused by irritation of the GI tract, motion sickness or impulses from the cerebral cortex to initiate vomiting.
Where is the chemoreceptor trigger zone for vomiting located?
located in the area postrema on the lateral walls of the fourth ventricle.
Motion sickness
motion stimulates receptors in the vestibular labyrinth of the inner ear
Impulses are transmitted mainly via the brain stem vestibular nuclei into the cerebellum, then to the chemoreceptor trigger zone, and finally to the vomiting centre to cause vomiting
What is regurgitation? And how does it differ from vomiting?
Regurgitation of undigested or partially digested food from the stomach
Happens without effort (contrast to vomiting)
What group of people is rumination common in?
Common in babies or individuals with developmental disabilities
Dyspepsia
Indigestion - discomfort or pain in the upper abdomen area
Functions of Small Intestine (3)
- Segmentation (churning)
- Propulsion (propagated peristaltic contractions)
- Migrating motor complex (fasting)
Functions of Large Intestine (6)
- No fed/fasting patterns of motility
- Proximal: re-absorption of fluid and electrolytes. Bacterial fermentation releasing SCFAs.
- Non-propulsive segmentation & mass movements
- Distal: final desiccation, reservoir / storage organ
- Mass movements
- Filling of the rectum triggers a series of reflexes in the internal and external anal sphincters that lead to defecation
What is the name of the test used to evaluate the function internal and external anal sphincters?
Manometry
Hirschprung disease & symptoms (3)
Congenital polygenic disorder resulting in loss of neurons from submucosal and myenteric plexi
Symptoms: constipation, megacolon, and a narrowed segment of colon in the rectum
What results would manometry of internal and external anal sphincters likely produce?
smooth-muscle internal sphincter: does not relax after rectal distention
external anal sphincter: functions normally
Name 3 types of diarrhoea
Secondary
Osmotic
Psychogenic
Diverticula
abnormal pouches of colonic wall
Name 3 types of anorectal dysfunction
Faecal incontinence
Haemorrhoids/piles
Rectal prolapse (rectocele & intussusception)
Defecation is difficult for people with what form of injury?
Spinal cord injury
Give 2 examples of obstructions of the lower GI tract
Tumours
Ulcers
What 3 gases in the GI system can form an explosive mixture when suitably mixed?
CO2
Methane
Hydrogen
Name 3 disorders of the large intestine
constipation
diarrhoea
IBD: ulcerative colitis
Disorders of Gut-Brain Interaction
Diverticulosis
Anorectal dysfunction
Name 3 disorders of the small intestine
Malabsorption
Coeliac disease
Haemochromatosis
Pancreatic failure
Inflammatoy Bowel Disease: Crohn’s Disease
What tests are carried out in the GI Lab? (5)
- High Resolution Oesophageal Manometry
- 24h pH and impedance testing
- High Resolution Ano-Rectal Manometry
- Capsule Endoscopy
- Hydrogen Breath tests
What is an important consideration for HRiM/24h pH/Impedance?
Invasive test - need calm, well informed environment
What is an important consideration for HRAM?
Invasive test- sensitive emotional test
What is an important consideration for capsules?
patient previously taken laxatives
BT-fasting, patients have lots of symptoms
What is an important consideration for BT?
fasting, patients have lots of symptoms
Indications for HRiM (4)
Dysphagia
GORD
Rumination Syndrome
Pre fundoplication assessment of swallow
Contraindications for HRiM (4)
Oesophageal Varices
Large pharyngeal pouches
Large oesophageal diverticulum
Unable to tolerate
Measurements in HRiM (5)
Spatiotemporal topographical
pressure Plot
UOS relaxation
Peristaltic wave
OGJ relaxation
Ampullary emptying
Interpretations in HRiM (4)
Distal Contractile Integral (DCI)
Contractile Deceleration Point (CDP)
Distal Latency (DL)
Integrated Relaxation Pressure (IRP)
Tests used to assess swallow function - Chicago Classification (4)
Single 5ml swallows - supine/upright, salty water (impedance)
Multiple rapid swallow (MRS) test
Rapid Drinking challenge (RDC)
Solid Swallows
CC 4.0 Cannot Be Applied? (4)
Post balloon dilation
Post Hellers myotomy/or POEM
Post Fundoplication
Large para oesophageal hiatal hernia
What is involved in a GI lab report? (6)
Basal pressures
Anatomy
Residual pressures
Mobility
Findings
Indication
DeMeester Score
Composite scoring system for acid reflux
- eliminate mealtimes from results
Ambulatory Reflux Testing (3)
Wired pH monitoring
Wireless pH monitoring
Combined impedance pH monitoring
What is measured in 24h pH and impedance monitoring? (3)
Liquid (Refluxate)—– Retrograde decrease in impedance
Air (Belching)———- Anterograde increase in Impedance
pH
What impedance change and pH change indicates an acid reflux event?
Decrease in impedance of >50% of baseline
Decrease in pH < 4
Indications for pH monitoring and impedance (3)
GORD
Rumination Syndrome
Pre fundoplication
GORD typical symptoms (4)
heartburn
belching
regurgitation
epigastric pain
GORD atypical symptoms (5)
chronic cough
Hx chronic chest infections
sore throat
hoarseness
silent reflux
AET
Acid Exposure Time
MNBI
Mean Nocturnal Baseline Impedance
- Impedance-pH metric assessing impaired mucosal integrity of the oesophagus due to chronic acid reflux exposure.
- MNBI < 2292 Ω considered abnormal
- Indicative of an inflamed oesophageal mucosa
PSPW
Post reflux swallow induced Peristaltic wave
-antegrade progression of impedance decline within 30 s of a reflux episode on a pH-impedance study, (ie a swallow).
-Facilitates chemical clearance of acidic refluxate
-Protects the lining of the oesophagus from acid insult
Symptom association probability (SAP)
A metric that expresses the statistical likelihood that the patients symptoms are related to reflux.
SAP >95% = Positive SAP
How long does a 24hr pH test need to be to be useful?
20 hrs
Supragastric Belching
air sucked in continuously
- acid
- chest discomfort
- nausea
What is considered an abnormal DeMeester score for Acid Reflux?
> 14.7
24hr pH & impedance monitoring
What does it measure? (3)
- Liquid (Refluxate)—– Retrograde decrease in impedance
- Air (Belching)———- Anterograde increase in Impedance
- pH
Indications for 24hr pH - typical symptoms (4)
Heartburn
Belching
Regurgitation
Epigastric pain +/- radiating
Indications for 24hr pH - atypical symptoms (5)
Chronic cough
Hx chronic chest infections
Sore throat
Hoarseness
Silent Reflux
Lyon Consensus - AET
Acid Exposure Time
Lyon Consensus - MNBI (3)
- impedance-pH metric assessing impaired mucosal integrity of the oesophagus due to chronic acid reflux exposure
- MNBI < 2292 Ω is considered abnormal
- Indicative of an inflamed oesophageal mucosa
Lyon Consensus - PSPW (3)
-antegrade progression of impedance decline within 30 s of a reflux episode on a pH-impedance study, (ie a swallow).
-Facilitates chemical clearance of acidic refluxate
-Protects the lining of the oesophagus from acid insult
Anorectal function (2)
Continence (keeping stool in)
Evacuation (of stool)
Factors Regulating anorectal function (3)
Faecal incontinence
Constipation
Evacuatory disorders
Anorectal Pathophysiology (5)
Anorectal dysfunction (x3)
Haemorroids
Rectal prolapse
Rectocele
Intussusception
Investigating Anorectal function (3)
High Resolution of Anorectal Manometry (HRAM)
Rectal Sensitivity Training (RST)
Balloon Expulsion Test (BET)
In the balloon expulsion test, what is considered a normal time?
<1min
High resolution Anorectal Manometry - indications (5)
- Referred after organic pathology excluded Constipation/Evacuation disorder
- Faecal incontinence
- Functional anorectal pain
- Pre-operative assessment of anorectal function (risk of postoperative incontinence & impaired evacuation)
- Assessment of patients after obstetric injury or traumatic birth
High resolution Anorectal Manometry - method (7)
- Measures anorectal muscle function
- Used to perform rectal sensitivity testing
- Pressure sensors (8 anal canal sensors and 2 rectal sensors)
- Spaced 1 cm apart (give a higher degree of spatial resolution).
- Topographical plots that create a ‘pressure picture’ of the anal canal and rectum.
- Colour coded.
- Characteristic pressure signature
London classification (4)
Part I Disorder of the Rectoanal Inhibitory Reflex
Part II Disorders of Anal Tone and Contractility
Part III Disorders of Rectoanal Coordination
Part IV Disorders of Rectal Sensation
Regulation of faecal continence (5)
Ability to control bowel movement
- functional
- structural
-neurological
- psychological
Factors affecting faecal continence (8)
External anal sphincter - voluntary
Internal anal sphincter - involuntary
Neurological
Rectal sensation
Neuromuscular co-ordination
Rectal capacity
Haemorrhoidal cushions
Anorectal angle :Puborectalis, ‘Sling’ Muscle
Anorectal Dysfunction: Faecal incontinence (4)
passive
urge
overflow
stress
Anorectal Dysfunction: Constipation (3)
slow transit
normal transit
IBS-C
Anorectal Dysfunction: Evacuatory disorders (3)
-Defecatory Dyssynergia
-Inadequate
defecatory propulsion
-Pelvic floor dysfunction
