Answer:
The answer to the question: What are the similarities of the mucosal lining of the duodenum, jejunum and ileum, would be: they share the same muscularis externa, the mucosa is the same muscularis mucosae and they all have intestinal epithelium.
Step-by-step explanation:
When talking about the small intestine, and its three sections, one would think that they are all the same, and should share the same features; and in part we would be right. There are some commonalities either between the three sections, or between at least two of the three sections. The ones above, are the more general similarities, although there are similarities between at least two of the sections with a difference in the third portion. However, the gross number of differences between the duodenum, jejunum and ileum is immense. The reason? Because each one of this parts performs a very unique and specific function in the process of absorption of nutrients and digestion. While the duodenum´s most important function is to continue the digestion of fats, carbohydrates and proteins, and mix the enzymes with the chyme, appropriately, the jejunum is the one responsible for basically absorbing almost all of the resulting nutrients of the chyme, while the ileum is the main responsible for absorbing vitamin B12, nutrients not absorbed by the jejunum and bile salts.