GI Motility Flashcards
peristalsis process
food in one region relaxation of anal region contraction of region with food food propelled on (moves to area of lower pressure) usu travels some distance along gut
peristalsis definition
propulsive motility of the gut, move food or chyme from one place to another
requres NO
mixing motion definition
mix secretions with food. not as neatly coordinated. localized contraction, no relaxation
mixing motions - process
presence of chemicals and food
contraction of region
chyme move to either side
with relaxation, chyme is mixed.
Mouth - mixing
mastication
mouth - propulsion
swallowing
mastication
chewing. unclear neural origin, not required for complete digestion
Swallowing - Stage 1
Buccal phase - coluntary
under voluntary control. tongue rolls food back to entrance of pharynx. tongue along roof of mouth from front to back
Swallowing - Stage 2
Pharyngeal phase
bolus of food stimulates afferents, synapse in NTS
controlled at reflex level. can take all sensory information and produce these actions
close nasopharynx, create channel for bolos
block trachea
Strokes and swallowing
strokes that damage NTS, have a patient with stroke, make sure they can swallow.
cough produced when swallowing wrong
produced by larynx= protective
Swallowing - Stage 3
Esophageal phase
presence of bolus in esophagus initiates peristalsis. food enters stomach mostly through gravity. peristalsis is clean up
primary peristaliss initiated by swallow, second to clean up debris
Motility of Stomach
peristalsis
under some conditions known as pyloric pump
Mixing in stomach
retropulsion (variant of peristalsis)
Peristalsis in Stomach
peristatltic waves travel down stomach and food moves relatively slowly.
pyloric pressure high, only liquid gets through pyloric valve.
Retropulsion in the stomach
peristaltic wave travels down stomach, peristaltic wave travels faster than chyme. most chime cant leave, turns back
Pyloric pump
stronger waves of peristalsis force chyme through pyloric sphincter,
Factors increasing Gastric emptying
“food here, get out”
comes from stomach
1. Stretch of gastric wall, vagal and myenteric reflex
2. Gastrin (increases production of gastric acid and motility)
Factors decreasing gastric emptying
arise from duodenum “wait I’m not ready”
make sure stomach doesnt dump food into SI too fast
- enterogastric reflex. distension, acid osmolarity proteins in duodenum, –>decrease gastric motility, increase pyloric tone
- Hormones - CCKPZ, Secretin –> increase mixing, decrease emptying
Small Intestine Mixing
Segmentation
Small intestine propulsion
peristalsis, with major purpose to distribute chyme for absorption
SI Segmentation
Mixing, may occur in groups, singly. requires background excitation from myenteric plexus
SI peristalsis
Frequency varies in different regions. faster in duodenum than ileum.
functions= move chyme to colon, spread chyme evenly.
travels about 5 cm before dying out
Neural Control of SI peristalsis
gastro enteric reflex,
local and CNS effects
Hormonal control of SI in peristalsis
Increase motility= gastrin, CCKPZ, insulin
decrrreased motilty= secretin and glucagon (released when acid enters duodenum. need to miz acid with pancreatic bicarb. dont want to push food past sphincter of oddi)
Peristaltic Rush
irritation in SI
increase peristaltic event
clears SI of irritenat = diarrhea
Migrating Motor Complex
during fasting, longer you go between meals, stronger these get
matches motilin
starts in stomach, of moderate strenght,
appears to move secretions through intestine. prevents enzymes from acting on damaging mucosa
Ileocecal valve
prevents bacflow, LI has different bacteria in ith that cause problems when there is backflow
Ileocecal sphincter
thickening of circular m. control entrance of chyme. normally mildly contracted
relaxation of ileocecal sphincter
gastric reflex (food in stomach causes ileum to relax, including sphincter) gastrin
Contraction of ileocecal sphincter
irritation
distention of the cecum (arises from the colon)
Mixing of colon
haustrations
propulsion of colon
mass movement
Haustrations
like sementation. strong contractions bc fecal material is becoming solid
mixing, triggered by chyme
near complete occlusion of lumen
absorb H2O,
mix HCO3 to counter acids secreted by bacteria
Mass Movement
propulsive motion. travels more than 20 cm repeats every 10-30 min until defacation initiatied by gastrocolic reflex duodenalcolic reflex parasympathetic
Defacation - part 1
local reflex.
distension. not strong, not enough to expel fecal matter
sensory motor enteric nervous system.
Defacation part 2
parasympathetic distension receptor in gut stronger part 1 and 2 are strong enough for expulsion if EAS is relaxed.
Defacation part 3
voluntary muscle to relax the EAS
