| 1 | The boundary between tunica adventitia which is serosa and submucosa is not obvious. | |
| 2 | Gastrointestinal serosa layer of the outer surface, so that the surface lubrication, easy activity. | |
| 3 | Insulin was as effective whether it was added on the mucosal or the serosal side. | |
| 4 | Plasma membranes of different cells make contact in all directions but there are no intercalated discs. | |
| 5 | Because of esophagus without serosal layer, it can easily pass through loose connective tissue directly adjacent organ invasion. |