Medicine Year 2 > GI Topic 2 - Upper GI tract > Flashcards

GI Topic 2 - Upper GI tract Flashcards

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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
How does H. Pylori infection affect gastric acid production?
* 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
26
How does NSAID use contribute to peptic ulcer formation?
* 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)
27
Describe the branches of the common hepatic artery
* Gastroduodenal artery * R gastric artery * Bifurcates into left and right hepatic arteries * Right artery gives off cystic artery
28
Describe the location of the greater sac
* Cavity in the abdomen inside the peritoneum but outside the lesser sac * Connected to lesser sac by the epiploic foramen
29
What is achalsia?
* 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
30
Describe the path of ingested food as it passes through the stomach
* Abdominal oesophagus * Lower oesophageal (cardiac) sphincter * Cardia * Body * Pyloric antrum * Pyloric orifice * Duodenum
31
What is the main side effect of proton pump inhibitors?
Increased risk of enteric infection e.g. C. Diff
32
Describe the process of swallowing and how it is controlled
* 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
33
What is the function of the circular muscle layer of the GI tract?
Constriction
34
What is the function of the parietal cells of the stomach?
Secrete HCl and intrinsic factor (needed for B12 absorption)
35
What causes disorders of accelerated gastric emptying?
* 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
36
Describe the structure and location of the greater and lesser omentum
* 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
37
Why is the greater omentum called the policeman of the abdomen?
* Immune function - contains collections of macrophages * Infection and wound isolation - prevents spread of infection by wrapping around infected area to isolate it
38
What type of cells are the chief cells of the stomach?
Cuboidal epithelial cells
39
Define a hiatus hernia
Weaknening of oesophageal ligament, stomach migrates forwards into chest, separation of sphincter and diaphragm
40
What common drug affects MMCs and therefore stomach motility?
Erythromycin is a motilin agonist - accelerates MMCs
41
Describe the contents of the submucosa of the GI tract
Meissner's submucosal plexus
42
Describe the structure of the oesophagus
* Upper oesophageal sphincter to lower oesophageal sphincter * Upper 1/3 is voluntary striated (skeletal) muscle * Lower 2/3 is involuntary smooth muscle
43
How is Gastric electrical stimulation used in the management of gastroparesis?
* 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
44
Describe the external anatomy of the stomach
* 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
45
How much saliva is produced per day?
0.5L/day
46
Describe the gastric phase of stomach function
* 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
Describe the innervation of the oesophagus
* Sympathetic and parasympathetic * Myenteric plexus * Parasympathetic - peristalisis regulation via vagus nerve * Sympathetic trunk
48
What is the function of the chief cells of the stomach?
Secrete pepsinogen and gastric lipase
49
List the steps involved in a migrating motor complex
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
List the risk factors for peptic ulcers
* Males * Smokers * Stress * Blood group A * Increased gastric acid secretion - history of GERD * NSAID use * Age 45+ * HLAB5 phenotype
51
List common diseases of oesophageal dysfunction
* Achalsia * Oesophagus in scleroderma * Nutcracker oesophagus * Diffuse oesophageal spasm
52
How is achalsia treated?
* 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
Where does H. Pylori reside? How is it able to do this?
* 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
What is the function of the columnar epithelial cells of the stomach?
Secrete alkaline mucin - protection from acidic contents and digestive enzymes
55
List the parts of the lesser omentum
1. Hepatogastric ligament - liver to lesser omentum of stomach 2. Hepatoduodenal ligament - liver to first part of duodenum
56
What is the function of the longitudinal muscle layer of the GI tract?
Shortening the GI tract
57
List the components of gastric secretions
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
What is the most superior part of the stomach called? What is its clinical significance?
Fundus - can see gas bubble in imaging
59
How does mastication aid digestion?
Decreases the food particle size, mixes food and saliva, increases the surface area of food
60
Describe the general organisation of the layers of the upper GI tract
1. Mucosa 2. Submucosa 3. Muscularis propria 4. Serosa/adventitia
61
Describe pathogenesis of gastric cancer
1. Superficial gastritis 2. Atrophic gastritis hypochlorrhydia 3. Dysplasia 4. Cancer
62
How is oesophagus in scleroderma treated?
Proton pump inhibitors e.g. omeprazole
63
What is the clinical name for delayed gastric emptying?
Gastroparesis
64
Describe the organisation of the mucosa of the stomach
* Folded into rugae, produces gastric pits * Epithelium is simple columnar * Lamina propria * Muscularis mucosae
65
What is the function of HCl in gastric secretions?
Converts pepsinogen to its active form pepsin Acidity kills ingested pathogens
66
What is the function of the G cells of the stomach?
Enteroendocrine cells, secrete gastrin
67
What is nutcracker oesophagus? How is it treated?
* Squeeze pressure of oesophagus too tight - pain on swallowing (dysphagia) * Functional swallowing intact - benign * No therapies
68
List the salivary glands
Parotid, submandibular, sublingual
69
Which arteries supply the greater omentum?
Left and right gastroepiploic arteries
70
Describe the management of peptic ulcer disease
* 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
Describe the lining of the oesophagus
Non-keratinised stratified squamous epithelium
72
Describe the function of the pyloric pump
* 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
What controls the pyloric orifice?
Pyloric sphincter
74
Describe the afferent and efferent pathways which control oesophageal motility
* 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
Describe the parasympathetic control of the salivary glands
Parotid - glossopharyngeal nerve (IX) Submandibular, sublingual - facial nerve (VII)
76
Describe the transition which occurs in those with Barrett's oesophagus
Simple squamous epithelium becomes columnar epithelium
77
What is oesophagus in scleroderma?
* Connective tissue disease * Weak peristalsis and lower oesophageal sphincter * Causes bad reflux, leads to oesophagitis
78
How is pyloric tone altered?
* 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
Describe the management of gastroparesis
* 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
What is the function of Meissner's submucosal plexus?
Controls secretion and blood flow of the GI tract
81
Describe the venous drainage of the oesophagus
* Azygous vein in the thorax (+ hemiazygous) * Inferior thyroid vein in the neck * Left gastric vein in the abdomen (drains to hepatic portal vein)
82
What is the main side effect of a vagotomy?
Delayed gastric emptying
83
How does the stomach facilitate storage of food?
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
Which substances stimulate acid secretion in the stomach?
* Histamine - secreted by enterochromaffin-like cells * Gastrin - acts on CCK 2 receptor * Acetyl choline - vagus nerve (parasympathetic) at muscarinic receptor
85
List the causes of gastroparesis
* Idiopathic * Longstanding diabetes with macrovascular disease * Drugs - opiates * Post-viral
86
What causes decreased gastric emptying?
* 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
How is GI motility function measured?
* Pressure - circular muscle function * Transit - radiolabelled isotopes, scintigraphy, breath tests, dynamic contrast radiography
88
What are the symptoms of gastroparesis?
* Abdominal pain * Nausea and (often delayed) vomiting * Poorly controlled gastroesophageal reflux * Malnutrition * Weight loss
89
How is gastric acid secretion inhibited?
* 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
What is the function of Auerbach's myenteric plexus?
Controls the motility of the GI tract
91
Define peptic ulcer
* 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
Describe the layers of the muscosa of the upper GI tract
1. Epithelium 2. Lamina propria 3. Muscularis mucosae
93
Describe the venous drainage of the stomach
* 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
Describe the arterial supply of the stomach
* 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
Describe the risk factors for gastric cancer
* Majority of cases have H. Pylori infection * Strong genetic link * Bacterial strain * Male * Smoking * Diet
96
What is the effect of prolonged untreated gastroesophageal reflux disease?
1. Oesophagitis (inflammation) 2. Barrett's oesophagus (metaplasia) 3. Oesophageal cancer
97
Describe the contents of the muscularis propria of the upper GI tract
1. Circular muscle 2. Auerbach's myenteric plexus 3. Longitudinal muscle
98
What is the effect of H Pylori infection?
Peptic ulcers
99
What is the function of the mucous in gastric secretions?
Protects the stomach walls from acidity, provides lubrication
100
What kind of organism is H. Pylori?
Gram negative helical bacterium
101
List the symptoms of gastric cancer
* Anorexia * Weight loss * Anaemia * Haematemesis * Melena * Bloating * Nausea/vomiting
102
How is gastric acid secretion reduced therapeutically?
* Vagus nerve intervention - vagotomy * Anti-histamine - cimetidine * Proton-pump inhibitor - omeprazole, lansoprazole, esomeprazole
103
When is gastric acid secretion at its peak?
1hr post ingestion
104
List the functions of the stomach
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
List the causes of peptic ulcer disease
* H. Pylori infection * NSAID use * Smoking * Stress * Behut disease * Zollinger-Ellison syndrome * Crohn's disease * Liver cirrhosis
106
Which foods directly stimulate Gastrin release?
Protein/peptides, coffee, foods high in calcium
107
List the symptoms of peptic ulcers
* 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
Which important anatomical structures are contained within the lesser omentum?
* Hepatic artery proper * Common bile duct * Portal vein * Lymphatics * Hepatic plexus All enclosed in Glisson's capsule (fibrous)
109
What is the function of the oesophagus?
Propel the food bolus from the mouth to the stomach
110
What are the effects of accelerated gastric emptying?
* Dumping syndrome - carbohydrate load, increased insulin secretion, low glucose - causes syncope/pre-syncope * Diarrhoea
111
How do parietal cells function to produce HCl?
* 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
How is H Pylori infection diagnosed?
* IgG antibody in seryum * Stool antigens - qualitative * Endoscopy - biopsy * 13C urea breath test - ingest 13C urea, measure CO2 exhaled
113
Which antibiotics can be used to treat H Pylori infection?
Amoxicillin, tetracycline, clarithromycin, metronidazole
Medicine Year 2
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