GI Motility - Eidelman Flashcards
What is are the factors in the state of the lumen?
Osmolarity, distension, acidity (pH) and concentrations of peptides, fatty acids, carbohydrates and other particles.
Picture of electrical signaling for contraction of the stomach.
What modifies the contractions? How?
Gastric contractions are modified by ACh and gastrin, which cause increased amplitude and duration of contractions
Also diodenal distention, proximal basal tone, motilin (and erythromycin), other mediators.
Small Bowel Post prandial movement
After a meal, brisk random waves and contractions. Migration from a few mm to more than 40cm. Carbohydrate meals produce more contractions than fortein and fat rich meals, which area fewer and shorter. Non-nutrient meals (water) produces the largest number of contractions.
Interdigestive Motor Complex (IDMC) or MMC (Fasting Migrating Motor Complex or Migrating Myoelectric Complex)
IDMC is a complex series of periods of variable contractile activity with distinct phases showing different contractile amplitudes, propagation, and regularity.
The pattern as a whole sweeps slowly down the small intestine in the fasting state and recurs at regular intervals proximal to distal.
Doesn’t continue into large bowel.
The switch between quiescent and active phases and their orderly migration along the bowel are functions of the ENS.
Phase I: 5-20min no spikes, phase II: 10-40mins intermittent spikes, phase III: 3-6 mins intense spikes. Begins in stomach or proximal jejunum and migrates aong small intestine. Repeats every 1-2h until meals.
Empties large particles (marbles) because pyloris opens up to 2cm. Prevents bacterial overgrowth and retrograde colon contamination.
Colonic Motility
Antegrade and Retrograde movements. Propagating and nonpropogating.
Migrating long spike bursts (MLSBs): aboral high amplitude (short time) propagating contractions aborally responsible for mass movement of feces.
Gastrocolonic response
Colonic phasic and tonic activity increased one to two hours after a meal (faster if more active or in babies), suppressed at night.
Requires a minimum caloric load of ~300kcal (200kcal would increase rectal muscle tone)
600kcal of fat induces the response easily
Non-nutrient volume of 500cc all at once would also stimulate.
At night: retrograde movements empty the rectum back into the sigmoid. Awakening (even not completely conscious) stimulates propogating and nonpropogating waves).
Resting anorectal pressures
Lower towards the rectum (22mmHg), higher towards the anal verge. Stimulation allows person to decide what to do with contents. Can revert back to sigmoid.
Problems with pelvic floor creates fecal urgency, incontinence and incomplete emptying of the bowel. Reflex of entering causes relaxation of internal sphincter and contraction of the external sphincter. Relaxing the anorectal angle is by 3 rings of the levator ani on the pelvic floor.
Unconscious sensory sampling of content by sensory receptors can sense content of stool or gas.
Need to distinguish incontenence and diarrhea.
