GI Topic 2 - Upper GI tract Flashcards

1
Q

Describe the intestinal phase of gastric function

A
  • Proteins in duodenum - gastrin release (excitatory)
  • Duodenum distention/presence of acidic chyme - enterogastric reflex (inhibitory)
  • Secretin released by S cells in response to acid, inhibit gastrin release (reduces affinity of parietal cells to gastrin)
  • CCK, GIP and peptide YY released in presence of lipids - inhibits gastrin release
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2
Q

What is the function of the mucous neck cells of the stomach?

A

Secrete mucous - protection of stomach walls from acidic contents and digestive enzymes

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3
Q

List the cell types of the stomach mucosa

A
  • Columnar epithelial cells
  • Mucous neck cells
  • Parietal cells
  • Chief cells
  • G cells
  • Stem cells
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4
Q

List the post-prandial phases of stomach function

A
  1. Cephalic
  2. Gastric
  3. Intestinal
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5
Q

Describe the gastric transit time of liquids compared with solids

A

Liquids leave the stomach 20 minutes after ingestion, solids take 3-4 hours

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6
Q

Describe the potential complications of a peptic ulcer

A
  • Bleeding
  • Gastric/duodenal perforation leading to acute peritonitis (indicated by extreme stabbing pain)
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7
Q

What causes increased gastric emptying?

A

Increased food volume (stretching of stomach walls)

Presence of digestive products of proteins - causes Gastrin secretion

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8
Q

How are peptic ulcers prevented?

A
  • Proton-pump inhibitor prescribed to those on long-term NSAIDs
  • Switch non-selective COX inhibitors for COX-2 NSAIDs
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9
Q

Describe the motility of the stomach in the interprandial period

A
  • Migrating motor complex, every 90-120 minutes
  • Regulated by motilin - produced by M cells in the small intestine
  • Stimulates fundus contraction, increases emptying of the stomach - cleanses the stomach
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10
Q

Describe the organisation of the muscularis propria of the stomach

A

Inner oblique, middle circular and outer longitudinal smooth muscle layers

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11
Q

Describe the secretions of:

  1. G cells
  2. D cells
  3. K cells
  4. S cells
  5. I cells
A
  1. Gastrin
  2. Somatostatin
  3. Gastric inhibitory peptide (GIP)
  4. Secretin
  5. Cholecystokinin (CCK)
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12
Q

What produces the basal motor activity of the stomach?

A

Interstitial cells of Cajal produces the basal electrical rhythm of the stomach

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13
Q

Describe the extrinsic reflexes which cause increased pyloric sphincter contraction

A

Signals travel from the stomach/duodenum to the prevertebral sympathetic ganglia which stimulates inhibitory sympathetic fibres

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14
Q

Describe the location of the lesser sac

A
  • Also known as omental bursa
  • Cavity in the abdomen formed by the greater and lesser omentum
  • Connected to the greater sac via the epiploic foramen
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15
Q

What is the function of pepsin in gastric secretions?

A

Endopeptidase - breaks down proteins to peptides

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16
Q

Describe the serosa of the stomach

A

Continuous with the greater and lesser omentum

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17
Q

What is the function of intrinsic factor in gastric secretions?

A

Needed for B12 absorption

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18
Q

Describe the cephalic phase of stomach function

A
  • Secretory phase - sight, smell or taste of food stimulates dorsal motor neurons of the vagus nerve
  • Vagal postganglionic muscarinic receptors in stomach body release acetyl choline, parietal cells secrete hydrogen ions
  • Release of gastrin from G cells stimulates HCl and pepsinogen release
  • Vagal action and gastrin stimulate histamine release from mast cells and enterochromaffin-like cells
  • Histamine acts on H2 receptors on parietal cells - causes more hydrogen ion secretion
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19
Q

Describe the pharmacological treatments for gastroparesis

A
  • SHT4 agonists - cisapride
  • D2 antagonist - metoclopramide, domperidone
  • Motilin agonist - erythromycin
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20
Q

List the contents of saliva

A
  • Mucous - lubrication
  • Amylase - digests starch
  • Bicarbonate - neutralises acid
  • Thiocyanate, lysozyme - bacteriocidal
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21
Q

Describe the innervation of the stomach

A
  • Autonomic - parasympathetic and sympathetic
    • Parasympathetic from vagus nerve branches
    • Sympathetic - T6-9 spinal nerves via the greater splanchnic nerve to form the coeliac plexus
  • Also has afferent pain transmitting fibres
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22
Q

How does pyloric sphincter function at normal tone?

A

Allows fluid chyme to empty, prevents passage of solid food

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23
Q

Describe the arterial supply of the oesophagus

A
  • Superior and inferior thyroid artery
  • Branches of the bronchial, intercostal, descending aorta, left gastric, left inferior phrenic and splenic arteries
  • Dense anastomoses in submucosa - infarction is rare
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24
Q

What is diffuse oesophageal spasm?

A
  • Rare
  • Rapid peristaltic contraction
  • Causes chest pain, can impair swallowing function
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25
Q

How does H. Pylori infection affect gastric acid production?

A
  • Lies in gastric glands, next to D cells
    • D cells function to sense acidity and produce somatostatin to inhibit gastrin production and decrease gastric acid production
  • H. Pylori increased the pH of gastric glands due to alkaline secretions, D cells do not sense acidity and somatostatin is not released
  • Increased gastrin production, increased gastric acid secretion
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26
Q

How does NSAID use contribute to peptic ulcer formation?

A
  • NSAIDs inhibit COX - catalyses prostaglandin synthesis
  • Prostaglandins stimulate neck and isthmic gastric/duodenal cells to secrete buffer layer of bicarbonate, underneath mucin blanket
  • Blockage of pathway - epithelium susceptible to damage (especially where already thinned e.g. due to H. Pylori infection)
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27
Q

Describe the branches of the common hepatic artery

A
  • Gastroduodenal artery
  • R gastric artery
  • Bifurcates into left and right hepatic arteries
  • Right artery gives off cystic artery
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28
Q

Describe the location of the greater sac

A
  • Cavity in the abdomen inside the peritoneum but outside the lesser sac
  • Connected to lesser sac by the epiploic foramen
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29
Q

What is achalsia?

A
  • No peristalsis therefore no movement of the food bolus
  • Lower oesophageal sphincter doesn’t relax - constant high pressure, functional outlet obstruction at bottom of oesophagus
  • Causes regurgitation of food, weight loss
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30
Q

Describe the path of ingested food as it passes through the stomach

A
  • Abdominal oesophagus
  • Lower oesophageal (cardiac) sphincter
  • Cardia
  • Body
  • Pyloric antrum
  • Pyloric orifice
  • Duodenum
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31
Q

What is the main side effect of proton pump inhibitors?

A

Increased risk of enteric infection e.g. C. Diff

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32
Q

Describe the process of swallowing and how it is controlled

A
  • Voluntary then involuntary
  • Opening of upper oesophageal sphincter - initially voluntary but once started involuntary
  • Controlled by ‘swallowing centre’ in the reticular formation of the brainstem
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33
Q

What is the function of the circular muscle layer of the GI tract?

A

Constriction

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34
Q

What is the function of the parietal cells of the stomach?

A

Secrete HCl and intrinsic factor (needed for B12 absorption)

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35
Q

What causes disorders of accelerated gastric emptying?

A
  • Usually history of previous gastric surgery e.g. Bilroth 1 or 2
    • Bilroth 1 - removal of pylorus
    • Bilroth 2 - removal of of part of small intestines
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36
Q

Describe the structure and location of the greater and lesser omentum

A
  • Double layers of peritoneum
  • Greater - attaches to the greater curvature of the stomach, hangs over the transverse colon
  • Lesser - attaches from the lesser curvature of the stomach to the liver
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37
Q

Why is the greater omentum called the policeman of the abdomen?

A
  • Immune function - contains collections of macrophages
  • Infection and wound isolation - prevents spread of infection by wrapping around infected area to isolate it
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38
Q

What type of cells are the chief cells of the stomach?

A

Cuboidal epithelial cells

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39
Q

Define a hiatus hernia

A

Weaknening of oesophageal ligament, stomach migrates forwards into chest, separation of sphincter and diaphragm

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40
Q

What common drug affects MMCs and therefore stomach motility?

A

Erythromycin is a motilin agonist - accelerates MMCs

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41
Q

Describe the contents of the submucosa of the GI tract

A

Meissner’s submucosal plexus

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42
Q

Describe the structure of the oesophagus

A
  • Upper oesophageal sphincter to lower oesophageal sphincter
  • Upper 1/3 is voluntary striated (skeletal) muscle
  • Lower 2/3 is involuntary smooth muscle
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43
Q

How is Gastric electrical stimulation used in the management of gastroparesis?

A
  • 2 electrodes, 1cm apart, 9cm from pylorus in greater curvature of the stomach
  • Stimulates high frequency low amplitude contractions
  • Does not increase gastric emptying, improves nausea/vomiting
  • Effective for diabetics
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44
Q

Describe the external anatomy of the stomach

A
  • Greater curvature around left side of the body
  • Lesser curvature around right side of the body
  • Cardial notch between the oesophagus and the fundus
  • Angular incisure between the lesser curvature and the beginning of the duodenum
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45
Q

How much saliva is produced per day?

A

0.5L/day

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46
Q

Describe the gastric phase of stomach function

A
  • Food distends the stomach, activating the vago-vagal reflex and short loop myenteric reflexes, which stimulate secretion of ACh, which causes increased gastric secretions
  • MMC replaced by contractions of variable amplitude and frequency, allowing for mixing and digestion
  • Pacemaker cells (interstitial cells of Cajal) generate rhythmic depolarisation at a rate of 3 cycles per minutes, additional input from neurohormonal sources
  • Increased gastric secretion (HCl and pepsinogen) mediated by the vago-vagal reflex and further stimulated by the presences of the products protein digestion, inhibited when pH < 2/3
47
Q

Describe the innervation of the oesophagus

A
  • Sympathetic and parasympathetic
  • Myenteric plexus
  • Parasympathetic - peristalisis regulation via vagus nerve
  • Sympathetic trunk
48
Q

What is the function of the chief cells of the stomach?

A

Secrete pepsinogen and gastric lipase

49
Q

List the steps involved in a migrating motor complex

A
  1. Prolonged quiescence
  2. Increased frequency of contractility
  3. Few minutes of peak electrical and mechanical activity
  4. Reducing activity, back to phase 1
50
Q

List the risk factors for peptic ulcers

A
  • Males
  • Smokers
  • Stress
  • Blood group A
  • Increased gastric acid secretion - history of GERD
  • NSAID use
  • Age 45+
  • HLAB5 phenotype
51
Q

List common diseases of oesophageal dysfunction

A
  • Achalsia
  • Oesophagus in scleroderma
  • Nutcracker oesophagus
  • Diffuse oesophageal spasm
52
Q

How is achalsia treated?

A
  • No cure (nerve permanently damaged), palliative care
  • Rigiflux balloon dilation - Sengstaken tube
  • Oesophagotomy - cut lower oesophageal sphincter
  • Peroral endoscopic myotomy - cut muscle layers from inside
53
Q

Where does H. Pylori reside? How is it able to do this?

A
  • Inhabits low pH of gastric pits - binds via specific receptor of gastric epithelium
  • Uses enzyme urease to break down urea (in gastric juice) to ammonium bicarbonate (ammonia and carbon dioxide) - constant production of alkaline protects from gastric acid
  • Has flagella to burrow into mucosa, protects from host response and antibiotics
54
Q

What is the function of the columnar epithelial cells of the stomach?

A

Secrete alkaline mucin - protection from acidic contents and digestive enzymes

55
Q

List the parts of the lesser omentum

A
  1. Hepatogastric ligament - liver to lesser omentum of stomach
  2. Hepatoduodenal ligament - liver to first part of duodenum
56
Q

What is the function of the longitudinal muscle layer of the GI tract?

A

Shortening the GI tract

57
Q

List the components of gastric secretions

A
  1. Hydrogen ions - parietal cells (HCl),
  2. Pepsin - secreted as pepsinogen by chief cells
  3. Intrinsic factor - parietal cells
  4. Mucous - simple columnar and mucous neck cells
  5. Water
58
Q

What is the most superior part of the stomach called? What is its clinical significance?

A

Fundus - can see gas bubble in imaging

59
Q

How does mastication aid digestion?

A

Decreases the food particle size, mixes food and saliva, increases the surface area of food

60
Q

Describe the general organisation of the layers of the upper GI tract

A
  1. Mucosa
  2. Submucosa
  3. Muscularis propria
  4. Serosa/adventitia
61
Q

Describe pathogenesis of gastric cancer

A
  1. Superficial gastritis
  2. Atrophic gastritis hypochlorrhydia
  3. Dysplasia
  4. Cancer
62
Q

How is oesophagus in scleroderma treated?

A

Proton pump inhibitors e.g. omeprazole

63
Q

What is the clinical name for delayed gastric emptying?

A

Gastroparesis

64
Q

Describe the organisation of the mucosa of the stomach

A
  • Folded into rugae, produces gastric pits
  • Epithelium is simple columnar
  • Lamina propria
  • Muscularis mucosae
65
Q

What is the function of HCl in gastric secretions?

A

Converts pepsinogen to its active form pepsin

Acidity kills ingested pathogens

66
Q

What is the function of the G cells of the stomach?

A

Enteroendocrine cells, secrete gastrin

67
Q

What is nutcracker oesophagus? How is it treated?

A
  • Squeeze pressure of oesophagus too tight - pain on swallowing (dysphagia)
  • Functional swallowing intact - benign
  • No therapies
68
Q

List the salivary glands

A

Parotid, submandibular, sublingual

69
Q

Which arteries supply the greater omentum?

A

Left and right gastroepiploic arteries

70
Q

Describe the management of peptic ulcer disease

A
  • Treat H. Pylori infection - antibiotics
  • Proton pump inhibitor to decrease gastric acid production e.g. omeprazole
  • Bismuth salts + sucralfate help with healing (without decreasing acid production)
  • Withdraw use of NSAIDs
  • Treatment if ulcer bleeding
71
Q

Describe the lining of the oesophagus

A

Non-keratinised stratified squamous epithelium

72
Q

Describe the function of the pyloric pump

A
  • Strong, peristaltic, ring-like contractions move from the mid-stomach downwards
  • As stomach becomes more empty, contractions start further up body of stomach
  • Normal pyloric tone - each waves forces several mls of chyme into the duodenum
73
Q

What controls the pyloric orifice?

A

Pyloric sphincter

74
Q

Describe the afferent and efferent pathways which control oesophageal motility

A
  • Efferent vagal pathway from non-vagal nuclei, nucleus ambiguous and dorsal motor nucleus
    • Moves down the oesophagus causing contraction of smooth muscle, moving food downwards
  • Afferent vagal pathway back to swallowing centre in brainstem
75
Q

Describe the parasympathetic control of the salivary glands

A

Parotid - glossopharyngeal nerve (IX)

Submandibular, sublingual - facial nerve (VII)

76
Q

Describe the transition which occurs in those with Barrett’s oesophagus

A

Simple squamous epithelium becomes columnar epithelium

77
Q

What is oesophagus in scleroderma?

A
  • Connective tissue disease
  • Weak peristalsis and lower oesophageal sphincter
  • Causes bad reflux, leads to oesophagitis
78
Q

How is pyloric tone altered?

A
  • Neuronal and hormonal control
  • Increased by CCK, secretin, gastic inhibitory peptide, vagus nerve action, enteric reflexes, extrinsic reflexes
  • Decreased by local myenteric reflexes (stretching of wall), gastrin release
79
Q

Describe the management of gastroparesis

A
  • Dietary
    • Small meals frequently
    • Liquid food tolerated better than solids
    • Nutritional support - post-pyloric feeding or nasogastric tube
  • Treat underlying cause
    • Limit opiates or other trigger medicines
    • Post-viral may improve with time
    • Improve diabetic control
  • Pharmacological - prokinetics
  • Endoscopic - botulinum toxin injection to pyloric sphincter
  • Gastric electrical stimulation - Entera device
80
Q

What is the function of Meissner’s submucosal plexus?

A

Controls secretion and blood flow of the GI tract

81
Q

Describe the venous drainage of the oesophagus

A
  • Azygous vein in the thorax (+ hemiazygous)
  • Inferior thyroid vein in the neck
  • Left gastric vein in the abdomen (drains to hepatic portal vein)
82
Q

What is the main side effect of a vagotomy?

A

Delayed gastric emptying

83
Q

How does the stomach facilitate storage of food?

A

Food stretches stomach walls, stimulates vago-vagal reflex (stomach sends signals to brainstem, signals back to stomach), relaxes the smooth muscles of the stomach to allow storage of more food

84
Q

Which substances stimulate acid secretion in the stomach?

A
  • Histamine - secreted by enterochromaffin-like cells
  • Gastrin - acts on CCK 2 receptor
  • Acetyl choline - vagus nerve (parasympathetic) at muscarinic receptor
85
Q

List the causes of gastroparesis

A
  • Idiopathic
  • Longstanding diabetes with macrovascular disease
  • Drugs - opiates
  • Post-viral
86
Q

What causes decreased gastric emptying?

A
  • Distention of duodenum
  • Irritation of duodenal mucosa
  • Acidity of duodenal chyme
  • Osmolality of chyme
  • Presence of breakdown products of digestion, especially digestive products of fats
87
Q

How is GI motility function measured?

A
  • Pressure - circular muscle function
  • Transit - radiolabelled isotopes, scintigraphy, breath tests, dynamic contrast radiography
88
Q

What are the symptoms of gastroparesis?

A
  • Abdominal pain
  • Nausea and (often delayed) vomiting
  • Poorly controlled gastroesophageal reflux
  • Malnutrition
  • Weight loss
89
Q

How is gastric acid secretion inhibited?

A
  • Gastrin secretion inhibited by low pH (<3)
  • Also stimulates somatostatin release - inhibitory (D cells of pancreas), GIP (K cells), secretin (S cells) and CCK (I cells)
90
Q

What is the function of Auerbach’s myenteric plexus?

A

Controls the motility of the GI tract

91
Q

Define peptic ulcer

A
  • Break in epithelium of stomach, duodenum or lower oesophagus causing erosion and ulceration, loss of surface lining, fibrous scarring
  • Causes long-term, chronic pain
92
Q

Describe the layers of the muscosa of the upper GI tract

A
  1. Epithelium
  2. Lamina propria
  3. Muscularis mucosae
93
Q

Describe the venous drainage of the stomach

A
  • Left and right gastric veins drain to the hepatic portal vein
  • Short gastric veins and left/right gastro-omental veins drain to the superior mesenteric vein (drain to the HPV)
94
Q

Describe the arterial supply of the stomach

A
  • All branches derived from the coeliac trunk
  • Common hepatic artery (proper) branches to give the right gastric artery (supplies the right inferior stomach) and gastroduodenal artery and continues to supply the liver
    • Gastroduodenal artery gives rise to the superior pancreaticoduodenal artery and the right gastroepiploic artery (supplies L inferior stomach)
  • L gastric artery supplies R superior stomach and gives off oesophageal and gastric branches
  • Splenic artery gives off pancreatic branches, passes behind the stomach and gives off the short gastric arteries (supplies the L superior stomach) and the left gastroepiploic artery (supplies the L middle stomach)
95
Q

Describe the risk factors for gastric cancer

A
  • Majority of cases have H. Pylori infection
  • Strong genetic link
  • Bacterial strain
  • Male
  • Smoking
  • Diet
96
Q

What is the effect of prolonged untreated gastroesophageal reflux disease?

A
  1. Oesophagitis (inflammation)
  2. Barrett’s oesophagus (metaplasia)
  3. Oesophageal cancer
97
Q

Describe the contents of the muscularis propria of the upper GI tract

A
  1. Circular muscle
  2. Auerbach’s myenteric plexus
  3. Longitudinal muscle
98
Q

What is the effect of H Pylori infection?

A

Peptic ulcers

99
Q

What is the function of the mucous in gastric secretions?

A

Protects the stomach walls from acidity, provides lubrication

100
Q

What kind of organism is H. Pylori?

A

Gram negative helical bacterium

101
Q

List the symptoms of gastric cancer

A
  • Anorexia
  • Weight loss
  • Anaemia
  • Haematemesis
  • Melena
  • Bloating
  • Nausea/vomiting
102
Q

How is gastric acid secretion reduced therapeutically?

A
  • Vagus nerve intervention - vagotomy
  • Anti-histamine - cimetidine
  • Proton-pump inhibitor - omeprazole, lansoprazole, esomeprazole
103
Q

When is gastric acid secretion at its peak?

A

1hr post ingestion

104
Q

List the functions of the stomach

A
  1. Storage of food
  2. Mixing of food with gastric secretions to produce chyme
  3. Acid secretion
  4. Slow, controlled emptying of its contents into the duodenum
105
Q

List the causes of peptic ulcer disease

A
  • H. Pylori infection
  • NSAID use
  • Smoking
  • Stress
  • Behut disease
  • Zollinger-Ellison syndrome
  • Crohn’s disease
  • Liver cirrhosis
106
Q

Which foods directly stimulate Gastrin release?

A

Protein/peptides, coffee, foods high in calcium

107
Q

List the symptoms of peptic ulcers

A
  • Abdominal (epigastric) pain - often occurs 3 hours after meal
  • Bloating
  • Waterbrash - sudden flow of saliva
  • Nausea/copious vomiting
  • Loss of appetite, weight loss
  • Haematemesis
  • Melena - black, tarry stool associated with upper GI bleeding
108
Q

Which important anatomical structures are contained within the lesser omentum?

A
  • Hepatic artery proper
  • Common bile duct
  • Portal vein
  • Lymphatics
  • Hepatic plexus

All enclosed in Glisson’s capsule (fibrous)

109
Q

What is the function of the oesophagus?

A

Propel the food bolus from the mouth to the stomach

110
Q

What are the effects of accelerated gastric emptying?

A
  • Dumping syndrome - carbohydrate load, increased insulin secretion, low glucose - causes syncope/pre-syncope
  • Diarrhoea
111
Q

How do parietal cells function to produce HCl?

A
  • H+/K+ ATPases actively transport H+ into stomach lumen, K+ into cells
  • K+ diffuse out of cells into the lumen
  • H+ supply maintained by carbonic anhydrase, catalyses reaction CO2 + H2O –> HCO3- + H+
    • HCO3- diffuses into blood, H+ into the stomach lumen
  • Cl- diffuse out of parietal cells through specialised transporter into lumen
  • Cl- supply maintained by antiporters - import Cl-, export HCO3-
112
Q

How is H Pylori infection diagnosed?

A
  • IgG antibody in seryum
  • Stool antigens - qualitative
  • Endoscopy - biopsy
  • 13C urea breath test - ingest 13C urea, measure CO2 exhaled
113
Q

Which antibiotics can be used to treat H Pylori infection?

A

Amoxicillin, tetracycline, clarithromycin, metronidazole