L22 - GI Motility Flashcards
what is swallowing?
The passage of food bolus from the oral cavity to the stomach
What does swallowing do? (2)
- protect the airway
- prevent entry of air into the stomach
What does swallowing involve?
Co-ordinated activity of muscles in the oral cavity, pharynx, larynx and oesophagus
(Partly voluntar, reflexive in nature)
What are the 3 different phases of swallowing?
- oral
- pharyngeal
- oseophageal
What is the swallowing reflex stimulated by?
Food bolus stimulating pressure receptors in the back of the throat and pharynx
What are the steps in the swallowing reflex? (3)
- stimulation of pressure receptors
- signals swallowing centre in brain = nerve impulses
- involuntary contraction in pharyngeal muscles = material into oesophagus
How many muscles does the swallowing reflex involve?
25 pairs
What is swallowing a key role of? (4)
Oral drug administration
- pathway to digestive system
- convenient route
- wide range of dosage forms
- timing with food
What is the motility in the stomach? (6)
- mixing and churning
- role in digestion
- formation of chyme
- peristalsis
- gastric emptying
- depends on viscosity
What is gastric emptying?
Exit to the small intestine
How is stomach motility involved in drug administration? (3)
- mixing and dissolution of drugs
- gastric emptying influences drug absorption
- drug stability
What is the motility in the SI? (3)
- mixed by segmentation
- movement by peristalsis
(Sequential activity in muscle bands) - coordinated by the enteric nervous system
What are the steps in peristalsis? (3)
- contraction of circular muscles behind food mass
- contraction of longitudinal muscles ahead of food mass
- contraction of circular muscle layers forces food mass forwards
What is the intestinal and colonic motility controlled by?
ENS
(Enteric nervous system)
What are the 2 main branching networks in the intestines?
- auerbachs (myenteric) plexus
- meissners (submucosal) plexus
What are the steps in enteric neurons controlling peristalsis? (3)/(4)
- sensory neurons detect food pressure and stretch
- motor neurons trigger muscle contractions/relaxations
- influenced by neurotransmitter and autonomic input
= ensures smooth coordinated and movement through GI
What controls the ENS? (3)
- sympathetic nervous system
- parasympathetic nervous system
- hormonal control
How does the sympathetic nervous system control the ENS? (3)
- fight or flight
- inhibits ENS
- dec peristalsis, blood flow, secretion and absorption
How does the parasympathetic nervous system? (3)
- rest and digest
- stimulates ENS
- inc peristalsis, blood flow, secretion and absorption
How does hormonal control control ENS? (2)
- inc by cholecystokinin, gastrin, motilin, serotonin, insulin
- dec by secretin and glucagon
How is intestinal motility involved in drug administration? (2)
- bioavailability - dissolution
- absorption - transit time
- distribution
Migrating motility complex
What is within the migrating motility complex? (5)
- recurring motility pattern
- regulated by electrical activity
- occurs between feeeding
- stomach to LI
- cleansing mechanism
How is the migrating motility complex involved in drug administration? (4)
- drug absorption (emptying, motility, timing of administration)
- controlled release drugs
- drug efficacy
- pharmacokinetics (onset of action, half life, bioavailability)
What is the motility in the large intestine - segmentation? (6)
Haustral shuttling
- localised contraction and relaxation of haustra (segmentation)
- mixing contents
- optimise absorption
- efficient water absorption
- stool formation
- support microbiome
