Lecture 45 - Control of Digestion Flashcards
What are the major functions of the gut?
- digestion
- absorption
- removal of waste products
- fermentation: breakdown of cellulose
- epithelial barrier to pathogens
How does fermentation occur in the gut?
Gut Microbiome / probiotics digest cellulose to deliver us with short chain fatty acids
Which is the largest immune system in the body?
The gut
Why is the epithelial barrier in the gut important?
- protect us from invaders in food
* protect us from our own microbiome
Which is the largest endocrine system in the body?
The gut
Describe the gut as a chemical refinery
- Mechanical crushing
- Mixing vats
- Solvents and catalysts
- product separation
- conveyor belt
- waste disposal
- control systems
What are the control systems of the gut?
- CNS
- ENS
- hormones
- muscle
Why is the pylorus important?
Separates with acid contents of the stomach and the base contents of the duodenum.
Controls the flow into the duodenum
How long is the gut in total?
7 metres
What are the basic elements of neural control of the GIT?
Local: ENS
Central: vagus and sympathetic pathways
• Cephalic phase
How is the smooth muscle of the gut controlled?
Pacemakers
which control:
• propulsion
• mixing
What is the longer distance, slow control of the GIT?
Endocrine
Controls:
• appetite (satiety, hunger)
• coordination
Describe the ENS
Network of neurons within the intestinal wall
Describe how the ENS changes along the length of the gut
Doesn’t change
What are the layers / plexuses of the ENS?
- Submucous plexus
* Myenteric plexus
Where does the submucous plexus lie?
Between the mucosa and the circular muscle
Where does the myenteric plexus lie?
Between longitudinal and circular muscle layers
What happens when a part of the gut is cut out and out in a dish?
Can still produce many of the basic functions
The pacemakers and sensory neurons are still present
What does the CNS do in the GIT ?
- Modulates
- Initiates
… the activity of ENS
What are the three basic functions of the ENS?
- motility of gut
- absorption of salt and water
- release of enzymes and hormones
Describe the motility pattern after a meal
Fed state: • stomach relaxation -- for storage • segmentation • peristalsis (• retropulsion)
What is segmentation?
Localised constrictions to mix up the contents
No propulsion
How does vomiting occur?
Anesis / Retropulsion
Describe the motility of the stomach when fasting
MMC: migrating motor complex
