Lecture 25: Motility of the GI tract Flashcards
What are the functions of motility in the GI tract?
- Movement at a controlled rate: propulsion and storage
- Mechanical digestion: Ingestion and increased surface area
- Mixing
- Exposure to absorptive surfaces
What are the feeding motility patterns in the GI tract?
- Storage
- Peristalsis
- Segmentation
Storage is a feeding motility pattern in the GI tract
- what is its function
- where does it occur
Storage - when you need to slow down movement
- Mainly in stomach & storage of waste material in large intestine
- Relaxation of smooth muscle
Peristalsis is a feeding motility pattern in the GI tract
- what is its function
- where does it occur
Peristalsis = propulsive - moves material quickly from one part of the tract to the other via contractions
- Oesophagus, stomach, small and large intestine
- Propulsive
Segmentation is a feeding motility patten in the GI tract
- what is its function
- where does it occur
Segmentation = mixing - moves material back and forth
- Small and large intestine
- Mixing & exposure to absorptive surfaces
What is the fasting motility pattern?
What is the fasting motility time period?
What are the 3 periods?
= Migrating motor complex MMC
Co-oridnated: stomach —> small intestine —> large intestine
- Occurs 4 - 5 hours after a meal
- Repeated every 2 hours
3 periods: Inactivity, Intermittent activity and Intense activity
What determines the type of motility that occurs?
The ENS system determent the type of motility
- Peristalsis
- Segmentation
The enteric system coordinates muscle to generate motility patterns and is regulated by a feedback loop
Gi smooth muscle is spontaneously active.
what does this mean?
What regulates this motility?
Smooth muscle contracts without external input
Basis of spontaneous activity = Basic electrical rhythm (BER) or slow wave
- Spontaneous variation in membrane potential produces AP’s which leads to the contraction of smooth muscle
- BER determine the frequency of contractions
- Strength of contraction is regulated by nervous and hormonal reflexes
Describe motility in the mouth - chewing
What is the function?
How is motility of the mouth controlled?
Function - Reduce size of food - Mixing with saliva - Tasting Control = voluntary - skeletal Reflex control of: - Strength - Frequency - Side of chewing
Descrive motility of swallowing
What is the function?
What are the stages?
Function - Rapid transfer of material from mouth to stomach - Pressure gradient Stages - Oral - Pharyngeal - Oesophagus
Describe small intestinal motility?
What is the function?
What are the motility patterns?
Overall function of stomach:
- Chemical digestion of food
- Absorption of nutrients, salts and water
Function of motility = mixing, propulsion and exposure to absorptive surfaces
Motility patterns
- Fasting = migrating motor complex
- Feeding = mainly segmentation and peristalsis
Describe the large intestine; colon ?
What is the function?
What are the motility patterns?
What are the mass movements?
Functions - temporary storage of faeces - Regulation of the salt and water content of faeces Motility patterns - Inactivity - Segmentation Mass movements - 3-4 times per day - Forces faeces into rectum
