GI Motility Flashcards
What is the contractile unit of the gut?
Smooth muscles cells except in the pharynx, upper esophagus and sphincter (skeletal)
What are the special structures on the cell membrane
Nexuses
Nexuses
Allows different ions to move freely between smooth muscle cells
Have multiple exits
Similar to the GJs
What are the two contractions of the smooth muscles of the gut?
Tonic and Phasic
What are the requirements for contraction?
Action potential (enteric nerve)
Phase 3 (plateau phase) - ICC
Phasic contractions
Takes seconds
Esophagus, small intestine and gastric antrum
Tonic contractions
Minutes to hours
Lower esophagus, cardia, internal anal sphincter
What are the phases of GI motility?
Oral (mechanical)
Esophageal
Gastric
Intestinal
What are the 2 stages of the oral phase?
Oral Stage: mastication, chewing, mandibular, trigeminal
Pharyngeal Stage: Swallowing, vagus, glossopharyngeal
Mastication/ chewing of the oral stage
Mechanical digestion (reducing size, increase surface area)
Lubrication by saliva
Enzymatic digestion
Mixing
Pharyngeal state of the oral phase
Swallowing - inhibits respiratory center
Pure motility- no digestion
Failure of the oral phase
Cerebrovascular injury (stroke)
Esophageal phase
20-60 mm, well organized
Relaxation of the stomach
Pure motility- no digestion
Esophageal phase contractions
No slow waves (myogenic, no ICC)
Contractions are controlled through vagus nerve
Diffuse Esophageal Spasm
When there’s no regular contraction so the stomach and esophagus aren’t relaxed
Acid reflux all the time
Treated with myotomy
What are the 2 contractions of the stomach?
Reservoir (storage)
Antral pump (moving)
What does gastric emptying entail (relaxation)?
Controlled by the size of particle after digestion
Protective mechanism
15 min- 8 hrs
Complete emptying 8-12 hrs
ENS hormonal control
Reservoir contractions
Tonic, continuous
Antral pump contractions
Phasic, single contraction
Sieving effect in the normal stomach
Movement of particles 1-3 mm from the stomach to the duodenum
Liquid > isotonic > hypocarolic (3 diff nutrients)
Protein > carbs > fat (how fast they pass)
What is sieving based on?
Size, calorie content and digestibility
Vomiting
- Metabolic Acidosis- loss of sodium bicarbonate
- Metabolic Alkalosis- severe vomiting, loss of gastric acid
What are the gastric disorders related to rate of gastric emptying?
- slowing- gastric ulcer, vagal injury, infection, hypothyroidism
- Acceleration- duodenal ulcer
What are the states of the gut?
Interdigestive state- MMC, motilin, no food
Digestive state- No MMC or motilin, food
Digestive state
3 motility patterns replace the MMC
Mixing, segmentation and short-distant peristalsis
What are the 3 motility patterns of the interdigestive state?
Migrating motor complex
Segmentation
Power propulsion (strong in large intestine)
(Enteric and extrinsic)
Large intestinal disorders
IBD/ diverticula- diarrhea/ constipation
Hirschsprung’s disease (congenital, lack ENS)
Megacolon (no ENS)
Dumping syndrome
Complication following Roux-en-Y and VSG medical treatment
Large Intestin Motility
Similar to the small intestine
Different intensity (more)
Anatomical consideration: taeniae, haustra
Hirschsprung disease symptoms
Swelling around belly
Vomiting (greenish-brown)
Constipation
Flatulence
Diarrhea
Failure to gain weight
Sever fatigue
