Week 2: Esophageal motility Flashcards
What is the main function of the esophagus?
transit of food to the stomach
Trick is
- dont choke
- dont aspirate food into the trachea
- don’t aspirate air into the gut
Describe esophageal manometry
UES - upper esophageal sphincter
LES - lower esophageal sphincter
At the UES you are above atmospheric pressure
as you go lower the pressure decreases but at the diaphragm above atmo pressure
esophageal manometry during a swallow
initially open and then snap shut
Pressure wave going down but the bottom is open and gravity can take bolus down before even the pressure wave gets there depending on the viscosity of what is being swallowed, this is why liquids can be swallowed faster than solids
stomach relaxes to prepare for the bolus to enter
Functions of the esophagus
4 listed
Reflexes involved in the initiation of swallowing
2 listed
Describe the oral or voluntary phase of swallowing
Moves food into the pharynx
Describe the pharyngeal phase of swallowing
- Larynx moves forward, epiglottis prevents entry into trachea and helps open UES
- soft palate prevents reflux into nasopharynx, provides passage into pharynx
Pharyngeal phase of swallowing
involuntarily and neuronally mediated through Vagal efferents
brain also turns of respiration which picks back up as soon as the UES closes
Describe UES regulation
- tonically contracted between swallows
- relaxes during swallows
Muscle types in the esophagus
Describe the muscles and nerves of the pharynx and upper esophagus
What drives peristalsis
entirely done by neurons contained in the wall of the gut in between the longitudinal and circular muscle fibers
IDentify structure and components
Locations of the principal networks of enteric neurons
- Myenteric plexus
- Submucous plexus
Identify structures and components
Describe peristalsis mechanism
You get a peristaltic contraction behind the bolus and a relaxation in front of the bolus which is in tune with the size, shape and chemistry of the bolus without any input from the brain through the combination of sensory neurons and efferent neurons of the enteric nervous system
Describe the peristaltic reflex
sensory neurons sense the bolus and interneurons to coordinate contraction and relaxation of motor neurons to move the bolus as needed
Regulation of GI smooth muscle peristalsis
bolus hits villi activating sensory neurons and data is transmitted through the interneurons to get a coordinated contraction and relaxation behind and in front of the bolus respectively
Muscles and nerves of the pharynx and upper esophagus
Peristalsis transmissions speeds
M2 receptor second messenger
inhibition of adenylate cyclase
Activation of K+ channels
M2 receptor targets
Heart
M2 receptor effects
Inhibition
M3 receptor second messenger
Stimulation of phospholipase C
M3 receptor targets
2 listed
- smooth muscle
- secretory glands
M3 receptor effects
2 listed
- Contraction (smooth muscle)
- secretion (secretory glands)
Cardiac muscle stimulation
increase adenylate cyclase
Cardiac muscle inhibition
decrease adenylate cyclase
Smooth muscle stimulation
Increase phospholipase C
Smooth muscle inhibition
Increase adenylate cyclase
Glandular stimulation
Increase phospholipase C
Inhibition of adenylate cyclase
M2 Gi coupled receptor
Activation of phospholipse C pathway
Excitatory neurotransmission to GI smooth muscle
Inhibitory neurotransmission to GI smooth muscle
LES regulation
Describe the overall mechanism of primary peristalsis
Describe the overall mechanism of secondary peristalsis
Question
C. Activation of M3 and M2 receptors on smooth muscle cells
Disorders of esophageal motility
3 listed
- Stroke
- Achalasia
- Reflux
Summary of esophageal motility
How common is induced dysphagia from stroke?
common - up to 65% of stroke patients
Swallowing phase effected by stroke-induced dysphagia
Loss of coordination of pharyngeal phase
Complications of stroke-induced dysphagia
- Pneumonia
- poor nutrition
Treatment of Stroke-induced dysphagia
- Physical therapy
- Modify texture of foods
What is Achalasia?
Loss of coordination of smooth muscle peristalsis
Swallowing phase effected by Achalasia
Lack of complete opening of LES so food remains in the esophagus leading to pain and regurgitation
Treatment of Achalasia
- Smooth muscle relaxants
- Surgery
Cause of loss of esophageal motility due to Reflux
Low resting pressure in LES
Phase of swallowing effected by reflux
Poor secondary peristalsis
Treatment of reflux induced loss of esophageal motility
- Symptomatic treatment - acid reduction
- Surgical treatment - Strengthen LES
