The eusophagus is the main tube which carries food from the mouth and pharynx to the stomach. It layers, from inside to outside, are: the mucosa, the submucosa, the muscle, and the serosa. Without cutting the eusophagus only the mucosa and the serosa layers are visible.

In this picture the eusophagus is labeled and you can see how it is very dorsal on the back of the cat. It is the line from the leftmost side of the picture towards the diaphragm, which the person is holding. The lungs and heart have been removed.
Diaphragm-anterior-aspect.jpg