| Question | Answer |
|---|---|
| give two areas of the GI tract that are under voluntary control | upper oesophageal sphincter (swallowing), and external anal sphincter (defecation) |
| what two types of muscle are in the musuclaris? | circular muscle and longitudinal muscle |
| what mediates enteric neurotransmission? | interstitial cells of Cajal |
| what do the myenteric interstitial cells of Cajal do? | serve as a pacemaker which creates the bioelectrical slow wave potential that leads to the contraction of smooth muscle |
| what does the enteric nervous system mediate? | reflex activity in the absence of CNS input (interprandial period) |
| what extrinsic factors influence the enteric nervous system? | vagal control: excitatory to non-sphincteric muscle, sympathetic control: inhibitory to non-sphincteric muscle, excitatory to sphincteric muscle |
| give three neurohormonal influences on the enteric nervous system | Motilin, opioid receptors, 5-hydroxy-tryptamine |
| measurement of motility function: transit | radiolabelled isotopes (breath tests and scintigraphy), dynamic contrast radiology |
| what sort of muscle does the upper and lower oesophagus have? | upper – circular. lower – longitudinal |
| name two conditions that can affect the striated (upper part) of the oesophagus | polymyositis (chronic inflammation of muscles) and myasthenia gravis |
| give two conditions that can affect the smooth muscle (lower part) of the oesophagus | scleroderma hard, thickened areas of skin) and achalasia |
| what happens in achalasia | your lower oesophageal sphincter fails to open during swallowing, so there's a backup of food in your oesophagus |
| give four disorders of oeosphageal motility | achalasia, nutcracker/jackhammer oesophagus, diffuse oesophageal spasm, oesophageal involvement in scleroderma |
| give treatments for achalasia | rigiflex balloon dilation, laparoscopic heller's myotomy, per oral endoscopic myotomy (POEM) |
| what's the oesophagus like in scleroderma | weak lower oesophagel sphincter, absent peristalsis, severe oesophagitis |
| what's nutcracker oesophagus associated with | pain on swallowing, functional swallow tho |
| two motility phases of stomach and small intestine | the interprandial period and the fed state |
| what complex is active during the interprandial (fasting) period? | the migrating motor complex |
| how frequently does the migrating motor complex occur? | every 90 minutes – it's a cyclic contraction sequence |
| what's the migrating motor complex regulated by? | motilin |
| what does the migrating motor complex act to do? | cleanse stomach and intestine |
| name the four phases of the migrating motor complex | prolonged period of quiescence, increased frequency of contractility, a few mins of peak electrical and mechanical activity, declining activity merging to next phase 1 |
| what is motilin and what is it produced by? | polypeptide hormone produced by M cells in small intestine |
| when is motilin secreted? | at 90 minute intervals |
| what does motilin act as? | 'housekeeper' of the gut – cleanses in time for next meal. stimulates contraction of gastric fundus and enhances gastric emptying |
| name a motilin agonist | erythromycin |
| describe the cephalic phase | secretory phase, vagally mediated, sight/smell of food leads to increased gastric secretion |
| what percentage of gastric secretion happens in the cephalic stage? | 20% |
| what happens in the gastric phase? | proximal gastric tone reduces and fundus expands to accommodate meal. stomach expands without increase in pressure |
| what's the mmc replaced with in the gastric phase? | by contractions of variable amplitude and frequency, allowing mixing and digestion |
| what's the frequency and direction of gastric muscular contractions controlled by? | 'gastric pacemaker' zone within proximal gastric body |
| what does the gastric pacemaker zone do? | generates rhythmic depolarisations at a frequency of 3 cycles per minute, which only trigger gastric smooth muscle contractions with additional neurohormonal input |
| what' s the emptying time for liquids in the stomach? | emptying time for inert liquids is 20 mins, liquids leave stomach earlier than solids, solids undergo mixing and churning |
| how long do solids take to empty | empty completely over 3-4 hours |
| what slows down gastric emptying? | nutrient content – fatty meals take longer to leave the stomach |
| how much per hour is delivered to duodenum for liquid foods? | 200kCal/hr |
| give 2 disorders of accelerated gastric emptying | dumping syndrome and diarrhoea |
| give four disorders of delayed gastric emptying | abdo pain, vomiting, malnutrition, poorly controlled gastro-oesophageal reflux |
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