Histo Phys-Esophagus Flashcards
What are the muscular layers of the esophagus?
Inner circular and outer longitudinal layers
What type of muscle exists in the three regions of the esophagus?
Upper 1/3 = striated. Middle 1/3 = mixed striated and smooth. Lower 1/3 = smooth.
What is unique about the submucosa of the esophagus?
There are esophageal glands found in it.
What layer of the GI tube is typically absent in the esophagus?
Serosa. There is a little bit further down towards the stomach.
Identify the different structures indicated below.
1) Non-keratinized squamous epithelium 2) Lamina propria 3) Duct of submucosal gland 4) Muscularis mucosa 5) Submucosal mucus glands
Why have mucosal glands in the esophagus?
Lubrication so food can pass easily
What structure is indicated below?
The z-line. It indicates the end of the esophagus at the GE junction.
CNS control centers for swallowing
Nucleus retrofacialis and nucleus ambiguus (striated muscle activation). Parasympathetic and sympathetic (smooth muscle control). Sensory afferents (vagus -> nucleus solitarius -> nucleus ambiguus). Swallowing center in medulla & pons controls involuntary swallowing and inhibits medullary respiratory center.
Enteric nervous system and Auerbach plexus control for swallowing
Controls peristalsis in lower 2/3 of esophagus
How do you initiate swallowing?
1) Tongue pushes food back and involuntary control of swallowing initiates 2) Tongue pushes down epiglottis 3) Vocal folds close the larynx 4) Larynx pulled upward 5) Food passes to esophagus
How does swallowing proceed as it passes through the esophagus?
1) Vagal relaxation of upper esophageal sphincter 2) Smooth muscle peristalsis 3) Lower esophageal sphincter relaxes 4) Food goes into stomach
When is peristalsis important when ingesting liquids?
Only when lying down. When standing gravity takes care of transportation.
What structures are indicated below?
*
What happens when you get some food slightly stuck in the esophagus?
Initiation of secondary peristalsis. This secondary peristalsis will continue until the esophagus is empty.
What happens if you swallow very rapidly?
Inhibition of peristalsis. Once rapid swallowing is done, a clearing wave of peristalsis comes to restore normal function to the esophagus.
How is normal food movement promoted in the esophagus?
Pressure gradients generated by the esophageal sphincters.
Stimulatory nerves in swallowing?
Cholinergic
Inhibitory nerves in swallowing
Sympathetic
What signals are sent and received from the myenteric plexus?
Receives: efferent CNS and afferent esophageal muscle signals. Sends: efferents to smooth muscle for peristalsis.
What explains the propagation of peristaltic waves in esophageal smooth muscle?
On response = constriction followed by a latency period then and off response = relaxation. The latency period is longer as you go down the esophagus.
How would peristalsis be affected in the esophagus after a vagotomy?
The upper 1/3 striated muscle will have decreased ability to relax. The lower 2/3 will still be the same due to on off response.
What causes relaxation of the LES?
Vagal stimulation causes relaxation of the LES
Substances that will cause an increase in LES pressure.
Generally substances released when the stomach has food in it.
Substances that cause a decrease in LES pressure.
Generally substances released when food is released further downstream.
Why are pregnant women at increased risk for GERD?
High progesterone levels decrease pressure in the LES
What does GERD correlate with?
Dropped pressure in the LES
