Lecture 24 GI physio Motility Flashcards
what are the 4 processes of GI tract?
Motility
Secretion
Digestion
Absorption
what are the functions of motility in GI tract?
Movement at controlled rate
Mechanical digestion
Mixing - food / secretions / enzymes
exposure to absorptive surfaces (contact)
what does the Movement at controlled rate include?
propulsion
storage
what does Mechanical digestion include?
ingestion / physical breakdown
increases SA
what kind of muscle is in the Mouth?
what kind of muscle is in the esophagus?
what kind of muscle is in the Anus?
Mouth = skeletal esophagus = both anus = skeletal
what are the muscle layers for the basis of GI motility?
Muscularis mucosae
Circular muscle
Longitudinal muscle - shortening
Motility programmes
what does the Muscularis mucosae do?
SA
what does the Circular muscle do?
reduce diameter
what does the longitudinal muscle do?
shortening
What does GI smooth muscle is spontaneously active mean?
Contracts without external input
Basic electrical rhythm (BER) or slow wave
GI smooth muscle activity controlled / co-ordinated
Modulation (i.e. influenced by):
whats Basic electrical rhythm (BER) or slow wave?
Spontaneous variations in membrane potential (pacemakers)
Produce action potentials
Result in contractions (if / when get to threshold)
what is the GI smooth muscle activity controlled / co-ordinated by?
ENTERIC NERVOUS SYSTEM (ENS)
Controls strength of contractions
Co-ordinates motility patterns
what does the ENTERIC NERVOUS SYSTEM (ENS) do?
controls GI smooth muscle activity.
coordinates GI smooth muscle to generate motility patterns.
Controls strength of contractions
Co-ordinates motility patterns
what is GI smooth muscle Modulation (i.e. influenced by):?
External inputs – CNS e.g. vagus nerve
Hormones
Local factors e.g. stretch
GI
what different motility patterns can occur generated by ENS?
Peristalsis
Segmentation
ENS determines type of motility that occurs, hows it modified?
by stretch / nerves /hormones / local feedback loops (e.g. enterogastric reflex)
what are the 2 types of motility patterns?
Fasting
Fed
whats the Fasting motility pattern in GI tract?
Migrating motor complex (MMC)
Co-ordinated – stomach -> small intestine -> large intestine
4 - 5 hours after a meal
Repeated every ≈ 2 hours
3 periods
whats the 3 periods of Fasting motility pattern in GI tract?
Inactivity
Intermittent activity
Intense activity
whats the function of Fasting motility pattern in GI tract?
House keeping
whats the Feeding motility patterns in GI tract?
storage
peristalsis
segmentation
for Feeding motility patterns in GI tract, whats storage?
Mainly stomach
Relaxation of smooth muscle (distension)
for Feeding motility patterns in GI tract, whats peristalsis?
Esophagus, stomach, small & large intestine
Propulsive
for Feeding motility patterns in GI tract, whats segmentation?
Small and large intestine
Mixing & exposure to absorptive surfaces
whats peristalsis?
Propulsion (+/- mixing)
Oesophagus, Stomach, SI, LI
Proximal squeeze, distal relax
whats segmentation?
Mixing
SI and LI
Contract/relax circular muscle
-> mix + contact
what are some specific motility patterns?
chewing and swallowing
gastric motility
intestinal motility
whats the function of motility in the mouth chewing?
Reduce size of food
Mixing with saliva
Taste
for Motility in the mouth - Chewing, hows it controlled?
Voluntary - skeletal muscle Reflex control of: - Strength - Frequency - Occlusion - Side of chewing
swallowing (deglutition)
whats the function?
rapid transfer of material from mouth to stomach
swallowing (deglutition)
hows it controlled?
start voluntarily
proceeds involuntary (reflex)
co-ordination of multiple muscles
need to protect airway
swallowing (deglutition)
hows it done in esophagus?
peristalsis (+/- gravity)
sphincters
Gastric motility
whats fasting?
Shrinks to small volume
Migrating motor complex
Gastric motility
Eating - delivery of food
what Series of motility patterns occur associated with?
Storage
Mixing
Mechanical digestion
Controlled delivery to intestine
Gastric motility
storage in the proximal stomach
receptive relaxation
relaxation of proximal gastric smooth muscle
Gastric motility
storage in the proximal stomach
whats receptive relaxation?
increase in stomach volume without increase in pressure
initiated by swallowing - nervous reflex
Gastric motility
storage in the proximal stomach
whats relaxation of proximal gastric smooth muscle?
reduced thickness - highly distensible
Gastric motility
Peristalsis
peristaltic waves
first 60 min gentle activity
60 - 300 min more intense activity
Gastric motility
Peristalsis
whats peristaltic waves?
initiated on greater curvature
~ 3 /min
spreads to antrum
Gastric motility
Peristalsis
what causes 60 - 300 min more intense activity?
presence of products of digestion (amino acids)
gastrin production
stimulates contraction
gastric motility
whats the roles of peristalsis in the stomach?
propulsion
combined with pyloric sphincter
retropulsion
mixing and mechanical digestion
gastric motility
Controlled delivery of chyme to duodenum
Regulation of gastric emptying through regulation of gastric motility
Composition of food modifies rate of emptying
Duodenum controls stomach
gastric motility
Controlled delivery of chyme to duodenum
whats Composition of food modifies rate of emptying?
Solids slower than liquids
Fats slow gastric emptying
gastric motility
Controlled delivery of chyme to duodenum
whats Duodenum controls stomach?
Hormonal
- GIP
Neural
- Enterogastric reflex
whats overall function of SI?
Chemical digestion of food
Absorption of nutrients, salts and water
for Small intestinal motility
whats the Functions of motility?
Mixing (chyme / chemicals / enzymes)
Exposure to absorptive surfaces -> contact
Propulsion (4-6 hours)
for Small intestinal motility
whats the motility patterns?
Fasting - migrating motor complex (MMC)
Feeding
- Mainly segmentation -> contact Peristalsis
whats the function of LI (colon) motility?
Temporary storage of faeces
Regulation of the salt and water content of faeces
for LI (colon) motility
whats the motility patterns?
18-24 hours
Inactivity
Segmentation
- Mixing and slow propulsion
Mass movements
- 3 - 4 time per day
- Force faeces into rectum
Defaecation
- Reflex responses / Voluntary control
- Brain / brain stem / spinal cord
for LI (colon) motility
whats segmentation?
Mixing and slow propulsion
for LI (colon) motility
whats Mass movements?
3 - 4 time per day
Force faeces into rectum
for LI (colon) motility
whats Defaecation?
Reflex responses / Voluntary control
Brain / brain stem / spinal
whats formed after colectomy
ileostomy
