Swallowing, gastric emptying and intestinal motility Flashcards
Where are the Touch R for swallowing
near opening of pharynx
Where is the integration center for swallowing
medulla oblongata (lower pons)
What n control the upper esophagus and pharynx
cranial nn
what n innervates the lower esophagus
vagus n
what mm are inn by the cranial and vagus nn
pharyngeal and esophageal striated and smooth m
What are the three phases of swallowing
oral phase
pharyngeal phase
esophageal phase
Which phase is voluntary in swallowing
oral. tongue to pharynx
describe the pharyngeal phase of swallowing
involuntary, reflex-respiration inhibited- epiglottis blocks trachea
soft palate blocks nasopharynx entry-way
pressure R in pharynx trigger
bolus directed into esophagus via relaxed upper esophageal sphincter
describe the esophageal phase of swallowing
involuntary
bolus from upper esophageal sphincter via peristalsis through lower esophageal sphincter–> stomach
What are the prtective effects of the upper esophageal sphincter
protect airway from swallowed material
protect airway from gastric reflux
What are the protective effects of the lower esophageal sphincter
protects esophagus from gastric reflux
During what phases of swallowing is the larynx elevated
end of oral all of pharyngeal and begining of esophageal
What initiates esophageal phase
peristaltic wave initiated by swallowing center.
secondary peristalsis is initiated by distention (only if primary wave not sufficient)
What nn are involved with esophageal phase
input from esophageal fibers to CNS and ENS modulate primary and secondary esophageal peristalsis
Swallowing induces relaxation of lower esophageal sphincter and?
proximal stomach
How do sphincters manage antegrade and retrograde movement
high resting pressure
Differentiate proximal stimuli and distal for sphincters
proximal cause relaxation, distal cause contraction
What needs to be coordinated for unidirectional movement of GI
smooth m contractions
neural stimulation
humoral stimulation
Describe structure upper esophageal sphincter
striated m
regulated by cranial nn
highest resting pressure
closed during inspiration
desribe structure lower esophageal sphincter
smooth muscle regulated by cholinergic stimuli and vagus n
What is the primary function of lower esophageal sphincter
allows coordinated movement
prevents reflux of gastric contents into esophagus
Describe the LES resting tone
Intrinsic myogenic properties
cholinergic regulation
Describe LES relaxation
intrinsic smooth m
vagus n
occurs after UES returns to high resting pressure
What inhibits the LES relaxation
VIP and NO
what allows for entry of food into the stomach
the distention or swallowing decreases LES pressure and makes it less than intragastric pressure
What is dysphagia
difficulty swallowing
What are some structural abnormalities to dysphagia
tongue
esophageal or pharyngeal wall out pouching
stomach protruding above diaphragm (hiatal hernia)
esophageal tumors
What are some functional abnormalities that can cause dysphagia
neurological defects, PD, Myasthenia Gravis
muscular layer defect
What are Tx for dysphagia
surgery- cut tight muscle
remove obstructing tumors
increase salivary function
What is Achlasia
special form of dysphagia from a dilated esophagus proximal to LES so that it fails to relax, peristalsis is impaired
What is the Tx for achlasia
wiring defect cannot be corrected
symptomatic relief to reduce LES pressure, gravity
What is GERD
LES resting pressure prevents reflux from esophagus usually but with GERD reduce LES resting pressure
What is it that refluxes in GERD, and what can it cause
gastric juice, causing esophagitis or erosion of esophageal mucosa
What is Tx for GERD
control gastric acid secretion
less R of esophageal mucus
Less HCO3 secretion from saliva
commonest disease
Where is the orad region of the stomach
fundus and proximal body
receives and stores food
Where is the caudad region
distal body and antrum
mixing and propeling
What is secreted in gastric lumen near LES/cardia
mucus and HCO3
What is secreted in gastric lumen near funds/body
H+, IF, mucus, HCO3, pepsinogens, lipase
What is secreted in gastric lumen near antrum and pylorus
mucus and HCO3
What is receptive relaxation
LES and stomach relax, vagovagal reflex of VIP, pressure in stomach does not increase with increased V
What can cause a rapid pressure increase in the stomach
disruption of vagus n- vagotomy
What is gastric accommodation
relaxation in response to gastric filling, dilate fundus
allows increased volume to keep P consistent
What n controls gastric accommodation
vagus and ENS
Where does gastric mixing happen
antrum
what occurs during gastric mixing
increased gastric contractility
the stomach contents of chyme is a positive stimuli for contractility
What substances can increase gastric mixing
ENS: Ach and Substance P
Gastrin
What stimuli are inhibitory to gastric emptying
duodenum contents: fatty acids, monoglycerides, acidic pH, volume/distention, hypertonicity, AA and peptides
What hormones can inhibit gastric emptying
CCK, secretin, GIP
what neural control is there over gastric emptying
intrinsic and extrinsic
Increased fluidity of stomach causes more or less contraction
more motility
Intense pain has what effect on stomach
inhibits motility and emptying
emotion has what effect on stomach
stimulates or inhibits motility and emptying
Where is the pacemaker zone of stomach and role
in body of stomach, sets rate of gastric peristalsis (3-5 slow waves/min)
What determines contraction force of stomach
degree od depolarization
duration of membrane depolarization
What affect do gastrin and Ach have on gastric contractions
increase amplitude and duration
increase contractility
what affect does norepinephrine have on gastric contractions
decreases contractility
What are the 3 mechanisms of gastric mixing
propulsion
grinding
retropulsion
what is stomach trituration
reduction of solid particle size
has to me less than 2 mm
emptying does not happen until solids are broken down
what molecules are emptied from stomach in order of greatest amount to least
liquid, carbs, protein, fat
Is gastric emptying carrying isotonic, hypertonic or hypotonic fluid
isotonic usually
What R are in the duodenum
pH, osmole, FA/monoglycerides, aa/peptides
what stimulus from duodenum slows gastric emptying
byproducts of fat and protein digestion
hypertonic chyme
<3.5 pH
Why is coordination of stomach with duodenum important
so chyme can be effectively processed by duodenum and not regurgitated
What are the neural and humoral events in duodenum that inhibit gastric emptying
relaxation fundus
inhibit antral contraction
stimulate pyloric contraction
What stimulates secretin release and its effects
acidic chyme
results in dec contractility of antrum, increased constriction of pylorus
What simtulates CCK and GIP and what are the effects
FA and monoglycerides
results in relaxation of gastric smooth m
increased constriction of pylorus
What stimulates gastrin and what are the effects
purely hormonal from peptides and aa
causes increased contractility in antrum
constriction of pylorus
What hormones cause increased constriciton of pyloric sphincter
CCK, GIP, secretin and gastrin
Describe the neural regulation of pyloric sphincter
SAN–>constriction
PAN–>vagus
constriction is Ach, relaxation is VIP
Approx when does the fasting state occur in regard to a meal
2 hours after a meal,
migrating myoelectri complex
What is Emesis
reflex vomiting, integration in medulla
What stimulates vomiting
gastric and duodenal distention and irritants
dizziness, inner ear dysfunction, moiton sickness
drugs
genitourinary injury
emetics: chem that cause vomiting
What is an emetic and where is the response center
ipecac- gastric/duodenal R that rigger chemo receptor in 4th ventricle of brain
What occurs in the vomit reflex
reverse peristalsis from SI->pylorus pyloric sphincter relaxes and stomach abs contract pylorus and antrum contract LES releaxes, gastric contents enter, UES relaxes
What are the 3 types of SI mobility
segmentation(mixing)
peristalsis(propulsion)
migrating myoelectric complex(sweeping of undigested contents during fasting state
What is the postprandial period of segmentation
part of segmentation when there are alternating contractions of circular sm m
Why is segmentation a slow process of propulsion and retropulsion
time for digestion and absorption
mixes chyme with digestive secretions
maximizes contact with mucosal layer
What is the postprandial phase of peristalsis
coordinated propulsive contractions of circular sm m
What causes the releaxation in front of bolus and contraction behind during perstalsis
relaxation in front: VIP and NO
contraction: ACh and Substance P
Describe the migrating myoelectric complex
new wave starts in stomach once previous wave passes distal ileum to move undigested material
What are the 3 phases of migrating myoelectric complex
quiescence, small disorganized contractions, strong propagating contractions
circulating motilin usually correlates to what
migrating myoelectric complex
What protective mech is the migrating myoelectric complex
prevent backflow of bacteria from colon to ileum
What part of SI has highest electrical rhythym
duodenum
What increases the burst of APs on slow waves
hormones, ENS, PAN and SAN via ENS
The contraction behind and relaxation in front of bolus is intrinsic or extrinsic
intrinsic ENS
What is intestinointestinal reflex
distention in one segment, relaxation in the rest of SI
What coordinates tone of ileocecal sphincter
normally contracted
ENS reflexes, long range extrinsic ENS and hormones
distention and ileum causes what in ileocecal sphincter? distension in ascending colon?
ileum->relaxation
ascending colon->constriction
What is the gastroleal reflex
increased gastric activity increases ileal motility and releaxation of the ileocecal sphincter
what is the purpose of the ileocecal sphincter
control rate of chyme entering colon so can absorb water and salts
What are the 3 primary types of colonic motility
Haustrations
Long duration contractions
mass movements
describe haustrations of colon
short duraction contrations, circular m–>mixing
describe long duration contractions
taeniae coli, mixing contractions that may cause propagation short distances in either direction
(not in proximal colon so can retain chyme)
describe mass movements of colon
high amplitude propagating contractions, sweep length of colon
1-3/day
high variability in colonic motility per person
Describe the control of colonic motility
primarily neural regulation via ENS, PNS, SNS via intrinsic control and extrinsic modulation
local reflexes from colonic distention
long range reflex from gastric distention- gastrocolic reflex
What is the effect of PAN on colon
vagus via ENS increases mixing in proximal colon
pelvic splanchnic nn via ENS cause increased contractions and propulsive movements in distal colon
What is the effect of SAN on colon
inhibits motility
postganglionics via abdominal sympathetic ganglia
Describe the internal anal sphincter
smooth m
involuntary control
majority of tone
describe the external anal sphincter
striated m
voluntary and involuntary control
defectaiton requires what stimulus
extrinsix neural input-> higher CNS
What results from distention in rectum
relaxation IAS reflex
rectosphincteric reflex: VIP and NO
reflex to constrict EAS
Is defectaion voluntary or no
coordinated volunatary and involuntary events
voluntary relaxation of EAS
contraction ABs
relaxation pelvic mm
What is Hirschsprungs disease
congenital megacolon fialure of ENS development impairs motility Aganaglionic segment rectosphincteric reflex impaired
Tx for hirschsprungs
surgical excision of diseased or aganglionic segment
Irritable bowel syndrome or disease is what
group of inflammatory conditions of colon and SI
What causes IBS/IBD
visceral hypersensitivity due to sensitization of afferent neural pathways
respond abnoramaly to stimuli
idiopathic, distention, inflammation, GI infections
partial dysmotility
What are the major types of IBD
Crohn’s disease and ulcerative colitis
How do you Dx IBD
assessment of inflammatory markers in stool then colonoscopy with biopsy of pathological lesions
