GI Motility 2
Terms
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copy deck
- 3 major tissue layers in GI tract
-
mucosa
submucosa
muscularis externa - componants of mucosa
-
Epithelial (squamous in esophagus, columnar in SI)
Lamina Propria
Muscularus Mucosa - purpose & composition of lamina propria
-
maintain epi layer (like basement membrane)
collagen & elastin - purpose of muscularis mucosa
- maintain structure lamina propria (folds & ridges)
- components of submucosa
-
collagen & elastin
nerves, vessels & glands - purpose & components of muscularis externa
-
peristalsis
inner is circular
outer is longitudinal - smooth muscle communicates via ...
-
gap junctions:
connexins form connexons
2 connexons line up & form ion channel - composition of serosa
- simple squamous epithelium
- 6 sphincters in GI tract
- UES, LES, Pyloric, Ileocecal, EAS, IAS
- esophageal peristalsis
-
primary & secondary
circular then longitudinal ctx
8-10 s (or 5-8 upright) - LES relaxes ...
- at initiation of swallow
- Phase shift
- amplitude of wave "travels" along length of tube
-
patient presents with:
dysphagia, belching, regurgitation of undigested food, minimal reflux - Achalasia
- barium eval with "beak like projection" & distended esophagus
- achalasia
- Achalasia results from
- degeneration of ganglion in muscular layers
- treatment for achalasia
-
pneumatic dilation (3% risk of rupture, 75% get relief)
surgery
botox (60% with relief at 1 year) - Mechanism of botox
-
Synaptotagmin (R) recognizes heavy chain
Internalized
Light chain is metalloproteinase (toxin)
LC cleaves SNAP 25 and ___________
Can't fuse with membrane protein to allow ACh into terminal - diffuse esophageal spasm
- uncoordinated peristalsis but LES with ability to relax
- 2 actions of stomach
-
mix food with secretions
push into intestines - muscle involved in mechanical digestion in GIT
- oblique muscle layer (innermost) of stomach
- normal epithelials of esophagus transformed into columnar
- Barett's esophagus
- progression of Barett's
-
normal
Barett's changes
with low grade dysplasia
with high grade dysplasia - control of gastric emptying
-
at pyloric sphincter
size dependent (dog experiment with liver & spheres) - pressures in stomach
-
amplitude increases from fundus to pyloric sphincter
phase shift - electrical activity in stomach
- little depolarization at top, increases as go down
- Slow wave potential
-
5/minute stomach
12/minute in SI
maintains potential near threshold - characteristics of small intestine motility
-
slow wave potential segmentation
peristalsis - segmentation
- "mixing" in SI, circular smooth muscle
- characteristics of large intestine motility
-
Haustral contractions
Mass movements - triangular units, slow to develop to relax, mix & remove fluid
- Haustral contractions (LI)
-
1-3 x per day
propulsion in LI
series contractions lasting 10-30 min - Mass movements (Haustral ctx cease)
- passage from SI to LI
-
at ileocecal sphincter
ileal distention, sphincter relaxes, colonic pressure causes feedback to tighten sphincter - effect of mass movement at rectum
-
rectum contracts
IAS relaxes
EAS gets spike in electrical activity
conscious decision to relax or contract EAS