swallowing, gastric emptying, and gastric motility Flashcards
phases of swallowing
oral
pharyngeal
esophogeal
oral phase
voluntary
bolus moved by tongue to pharynx
pharyngeal phase
- involuntary
- initiated in response to pressure receptors in pharynx
- directs bolus into esophagus via relaxed UES
- respiration inhibited
esophageal phase
involuntary
- primary peristaltic wave: bolus from UES via peristalsis through LES to stomach
- secondary peristalsis- initiated by distension, occurs only if primary wave not sufficient
- both primary and secondary peristalsis modulated by CNS and ENS reflexes
LES control
resting tone set my intrinsic myogenic properties and cholinergic regulation
relaxation due to vagus, VIP, and NO
swallowing and/or esophageal distention decrease LES tone
achalasia
absence of relaxation dilated esophagus proximal to LES LES fails to relax peristalsis impaired in distal 2/3s unknown mechanism, possibly loss of VIP and/or NO no treatment
GERD
- LES low resting tone, allows reflux
- low bicarb in salivia
Orad region
fundus and proximal body
receives and stores food
caudad region
distal body and antrum
mixing and propelling
LES and cardia
prevention of reflux entry of food regulation of belching mucus bicarb
fundus and body
resevoir tonic force during emptying -H -IF mucus -bicarb -pepsinogens lipase
antrum and pylorus
mixing grinding sieving regulation of emptying mucus bicarb
increase contractility
distension fluidity of chyme (increased fluidity increases emptying) Ach substance P gastrin
inhibitory to gastric emptying
distension in duodenum presence of FAs, monoglycerides, acidic pH, hypertonicity, AA, and/or peptides in duodenum CCK secretin GIP NE
gastric mixing
propulsion
grinding
retropulsion
trituation- reduction of particle size, must be <2mm to leave stomach
relative rates of gastric emptying
liquid > carbohydrates > protein > fat
isotonic fluid >hypertonic or hypotonic
pyloric sphincter control
constriction: CCK, secretin, gastrin, sympathetics
relaxation: parasympathetics, vagus, Ach constricts, VIP relaxes
migrating myoelectric complex stomach
fasting state, every 75-120min, starts 2 hours after meal
burst of strong antral electrical activity for 5-10minutes with relaxation of pylorus
‘cleans’ tract from stomach thru SI
Emesis
stimulated by
- gastric and duodenal distension or irritants
- dizziness, inner ear dysfunction, motion sickness, pregnancy
- drugs
- GU injury
- emetics (tigger either chemoreceptors or gastric/duodenal receptors)
segementation
postprandial period- alternating contractions of circular smooth m
slow process of propulsion and retropulsion:
- allows for digestion time
-mixes
maximizes contact w/mucosal layer for absorption
peristalsis
postprandial- coordinated propulsive contractions of circular smooth m
relaxation in front of bolus (VIP and NO)
contraction behind bolus (Ach and supstance P)
migrating myoelectric complex
new wave begins in stomach once wave had passed distal ileum
3 phases: quiescence, small disorganized contractions, strong propagating contractions (5-10min)
repeats every 75-120 min during fasting
correlated w/high levels of motilin
slow waves
duodenum highest rate 11-13/min
jejunum 10-11/min
ileum 8-9/min
colic motility
haustrations
loing duration contractions
mass movements
