Smith: Esophageal Motility Flashcards
5 steps of swallowing
- elevation of the tongue
- closure of the nasopharynx
- UES relaxation
- closure and protection of airway
- pharyngeal peristalsis
Three muscles that constrict during swallowing
Superior, middle, and inferior pharyngeal constrictor muscles
Muscle that relaxes during swallowing
Cricopharyngeus muscle
The UES has a resting pressure of about (blank)mmHg while the LES has a resting pressure of about (blank)mmHg
90mmHg; 20mmHg
What triggers primary peristalsis?
swallowing in the esophagus
The pressure wave that moves down the esophagus is coordinated with opening of the (blank), which relaxes before the propagating contraction.
lower esophageal sphincter (LES)
The upper third of the esophagus is (blank), while the lower third is (blank)
striated; smooth
What is the nerve plexus called between the circular and longitudinal layers?
myenteric plexus
The proximal portion of the esophageal body is composed of (blank) muscle and is innervated by somatic lower motor neurons whose cell bodies are located in the (blank)
striated; nucleus ambiguous (NA)
The more distal portion of the esophageal body is composed of (blank) muscle and is innervated by vagal preganglionic fibers whose cell bodies are located in the (blank)
smooth;dorsal motor nucleus (DMN)
A bolus of food stimulates stretch receptors in the pharynx. The pharynx then contracts sequentially and what relaxes?
Upper and lower esophageal sphincters
Vagus nerves arising from the NA release ACh directly onto the (blank) muscle where they activate nicotinic receptors on Skeletal Muscle Fibers to produce (blank).
skeletal; contraction
Vagus nerves arising from the DMN release Ach where they activate Nicotinic receptors on myenteric inhibitory and excitatory motor neurons to the (blank) muscle to produce relaxation and latency followed by contraction. What causes relaxation?
smooth; NO
What regulates the latency of esophageal contractions?
NO
Peristalsis induced by swallowing is called (blank), while peristalsis induced by esophageal distention is called (blank)
primary; secondary
Secondary peristalsis is triggered by distention in the (blank) muscle portion of the esophagus.
smooth
In secondary peristalsis, contraction occurs where in relation to the bolus? This is followed by a descending pressure wave that is coordinated with (blank) opening.
Closer to the mouth; LES
What does vagal stimulation do to the LES?
Relaxes it
What does tetrodotoxin do?
Blocks the vagal stimulation to the LES; inhibits relaxation
What is the inhibitory neurotransmitter that mediates esophageal relaxation?
NO
What does hexamethonium do?
Blocks relaxation by blocking vagal stimulation
What do anticholinergic drugs do to the LES?
Decrease LES pressure; This means that part of the LES tone is produced by cholinergic excitatory neurons releasing ACh in the LES
Symptoms of esophageal dysfunction
Gastroesophageal reflux symptoms
Dysphagia
Esophageal pain
Failure of pharyngeal propulsion and bolus clearance can be seen in this disorder
myasthenia gravis
