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2nd Year Med > Upper GI Physiology/Gut Motility > Flashcards

Upper GI Physiology/Gut Motility Flashcards

1
Q

what areas of the GI tract are under voluntary control?

A

upper oesophageal sphincer - swallowing
external anal sphincter - defacation

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2
Q

what are the 2 main components of the enteric nervous system?

A

submucosal (meissners) plexus
myenteric (auerbachs) plexus - inbetween CM and LM

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3
Q

what do the CM and LM do?

A

CM - allows squeezing/increased pressure allowing contents to be moved around
LM - squeezes to shorten diameter to allow forward movement

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4
Q

what are the interstitial cells of cajal?

A

pacemaker function
lies in myenteric plexus
produce basic electrical rhythm (BER) determining how often a gut area can contract
higher BER in proximal than distal

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5
Q

what is the function of the enteric nervous system?

A

mediates reflex activity in absense of CNS input (interprandial period)

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6
Q

what is the enteric nervous system influenced by?

A

extrinsic factors:
vagal control - excitatory to non-sphincteric muscle
sympathetic control - inhibitory to non-sphincteric muscle (excitatory to sphincter muscle)
neurohormonal influences (opioid receptors, motilin)

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7
Q

describe the measurement of motility function

A

pressure (circular muscle function)
transit (radiolabelled isotopes, breath tests, scintigraphy, dynamic contrast radiology)

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8
Q

what is the innervation of the oesophagus?

A

sympathetic - sympathetic trunk
parasympathetic - vagus nerve

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9
Q

describe the muscular structure of the oesophagus?

A

prox 2/3 - striated voluntary muscle
dist 1/3 - smooth muscle

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10
Q

what is a hiatus hernia?

A

weakness of diaphragmatic hiatus allowing stomach to partially move into the chest resulting in increased reflux

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11
Q

what diseases can be diagnosed by manometry in the oesophagus?

A

achalasia - lower oesophageal sphincter less responsive, lower peristaltic function
oesophagus in scleroderma - weak LOS, absent peristalysis, severe oesophagitis
jackhammer oesophagus - pain on swallowing (still functional)

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12
Q

what is the interprandial period controlled by?

A

migrating motor complex

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13
Q

what is the interprandial period?

A

cleansing of gut in preparation for next meal
cyclic contraction sequence occuring every 90 minutes
regulated by motilin

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14
Q

what are the 4 phases of the interprandial period?

A
  • prolongued quiescence
  • increased frequency of contractility
  • a few minutes of peak electrical/mechanical activity
  • declining activity merging to next phase 1
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15
Q

what is motilin?

A

polypeptide hormone produced by M cells in small intestine
secreted in 90 minute intervals
cleanses gut
stimulates contraction of gastric fundus and enhances gastric emptying

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16
Q

name a motilin agonist

A

erythromycin

17
Q

how can the gastric fundus/body accomodate large volumes?

A

volume increases up to 1.5l
due to receptive relaxation

18
Q

explain the process of gastric mixing

A

upper stomach muscles contract weakly (3 per minute) beginning in the middle of the gastric body and travelling to pylorus
occurs due to BER from pacemaker cells in stomach
contractions increase in force distally (major mixing - antrum)
contents form layers based on density (fats floating to top/emptying last)

19
Q

explain the process of gastric emptying (meal related motility stage 3)

A

liquids rapidly leave (20 minutes)
solid emptying is reguated (duodenal acid exposure can be harmful)
solids mixed/churned with gastric juice and can empty when rize reduced to 2mm

20
Q

what are the 3 phases of meal related motility?

A

cephalic
gastric
intestinal

21
Q

what is the cephalic stage of meal related motility?

A

secretory phase (vagally mediated)
sight/smell of food increases gastric secretion (20% of total)

22
Q

explain the gastric phase of meal related motility

A

stomach expands without pressure increase
MMC replaced by contractions of variable amplitude/frequency allowing mixing/digestion
frequency/direction of contractions controlled by gastric pacemaker (rhythmic depolarisations at 3 per minute triggering SM contractions with neurohumeral input)

23
Q

how much food is delivered to duodenum per hour?

A

200kcal

24
Q

explain the physiology of gastric emptying

A

antral pressure higher than gastric body/duodenum
as intra-gastric pressure rises, pylorus opens briefly
small amount of chyme passes to duodenum
most gastric content propelled back to stomach (more mixing)

25
Q

what can the duodenal mucosa sense from the stomach?

A

acidity
osmotic pressure
fat/AA presence (fat in duodenum inhibits gastric emptying)

26
Q

name some disorders associated with accelerated gastric emptying?

A

dumping syndrome
diarrhoea

27
Q

name some disorders associated with delayed gastric emptying?

A

abdominal pain
vomiting
poorly controlled gastro-oesophageal reflux
malnutrition

2nd Year Med (18 decks)

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