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Let’s continue our USMLE Review with Anatomy from the Gold Standard USMLE Step 1 Audio Review program.
Play USMLE Audio MP3 03 02 Anatomy The Esophagus Below
Begin 03 02 Anatomy The Esophagus Transcription
What type of tissue forms the mucosa of the esophagus?
- Nonkeratinized stratified squamous epithelium.
And what supports the mucosa?
- The lamina propria.
The lamina propria, this loose connective tissue layer, is separated from the submucosa by what?
- By smooth muscle, also called muscularis mucosa.
What glands are in the submucosa?
- Small mucous glands whose long ducts empty into the esophageal lumen. Around all of this is a two layer muscle coat.
What is the inner layer?
- Closely wound circular muscle
And the outer layer?
- Longitudinal muscle.
What type of muscle comprises these two layers in the upper esophagus?
- Striated muscle.
The striated muscle of the esophagus runs from the pharynx to approximately what level?
- The level of the aortic arch.
What happens to this striated muscle, the circular layers surrounding the submucosa and then the longitudinal layer surrounding the circular layers at the level of the aortic arch?
- It gradually transitions into smooth muscle.
Finally what layer surround the outside of the esophagus?
- The adventitia containing many elastic fibers.
What is not surrounding the outside of the esophagus unlike the rest of the digestive tract?
- There is no serosa or serous membrane.
Because there is no serosa or serous membrane around the esophagus, what difficulty is encountered in surgery upon the esophagus?
- Difficulty in obtaining a leak proof anastomosis.
What cranial nerve innervates the striated muscle surrounding the esophagus down to the level of the aortic arch?
- The cranial accessory nerve, or cranial nerve eleven.
And upon branches of what other cranial nerve do these fibers of cranial nerve eleven reach the striated muscle upon?
- They travel upon branches of the vagus.
And what cranial nerve innervates the smooth muscle of the esophagus including the smooth muscle in the submucosa and the smooth muscle surrounding layers from the aortic arch level down to the cardia level?
- Cranial nerve ten, the vagus.
Below what pharyngeal structure does the esophagus begin?
- The inferior pharyngeal constrictor.
And what two structural landmarks mark the beginning of the esophagus?
- The sixth cervical vertebrae and the cricoids cartilage of the larynx.
What structure of the esophagus is present at this level of the sixth cervical vertebrae and the cricoids cartilage at the very beginning?
- The upper constriction sphincter of the esophagus.
Now the esophagus ends at the transition into what structure?
- The cardia of the stomach.
And at what level is this?
- Just below the diaphragm at the level of the tenth to twelfth thoracic vertebrae.
****END OF TRANSCRIPTION****
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