Lecture 4: Esophagus Pathophysiology Flashcards
What is the job description to esophagus?
- To propel swallowed food into stomach
- Prevent gastroesophageal reflux
- clear refluxed material back into stomach
- Vomiting and belching
Where is esophagus located?
- originates in neck
- ends in stomach
- passes through RIGHT CRUS of diaphragm
What are the two types of muscles located in the esophagus?
Proximal portion is STRIATED (circular)
Distal portion is LONGITUDINAL (smooth)
What are types of diseases that the striated musscle portion of the esophagus can be affected by?
- Polymyositis
2. myasthenia gravis
What are the types of disease that the smooth muscle portion of the esophagus can be affected by?
- Scleroderma
2. Achalasia
What are the key characteristics of the upper esophageal sphincter?
- Striated muscle
- separates pharynx from esophagus
- composed of 3 adjacent muscles
i. inferior pharyngeal constrictor
ii. cricopharyngeus
iii. Cervical esophagus - prevents AIR ENTRY into GI tract and reflux of gastric contents into pharynx
- allows belching and vomiting; allows food into esophagus
What are the key characteristics of the gastroesophageal junction?
- comprised of two sphincters
i. lower esophageal sphincter
ii. Diaphragm - Anchored in place by phreno-esophageal ligament
What is achalasia?
When you can’t relax your lower esophageal sphincter when swallowing
Is there a serosal layer in the esophagus?
NO SEROSAL LAYER
Where do lymphatics of the esophagus come up to?
Comes up to the epithelium
Cancer of esophagus is rapidly spreading disease because of how close lymphatics are
When is the process of swallowing voluntary? Involuntary?
Voluntary = pharynx
Involuntary = esophagus
Act of swallowing activates esophageal activity
What innervates the skeletal muscle?
Nucleus ambiguous
Contact is DIRECT
What innervates the smooth muscle of the esophagus?
DMX (dorsal motor nucleus of X)
Has to go through myenteric plexus
What are the characteristics of vagal dorsal motor nucleus innervation to striated muscles of esophagus?
- Caudal inhibitory pathways
- NO is neurotransmitter
- Rostral excitatory pathways
- aCH is excitatory
What does swallowing do in terms of innervation?
Swallowing activates INHIBITORY PATHWAYS FIRST (to relax shit)
Simultaneous inhibition of entire esophagus (distal > upper)
Followed by sequential activation of excitatory pathways
What is the cholinergic gradient in the SMOOTH muscle portion of esophagus?
Cholinergic (excitatory) is marked proximally
Noncholinergic (inhibitory) is distal
This leads to peristalsis
What does the lower esophageal sphincter do at rest?
Closed tonically
Pressure falls within 1.5-2.5 seconds of swallowing
Remains low for 5-6 seconds
What are the three mechanisms involved in the regulation of basal LES tone?
- swallow induced relaxation
- cessation of tonic neural excitation
- NANC inhibitory neurons (NO), inhibition of cholinergic neuron