Final answer:
The submucosa layer of the alimentary canal contains blood vessels, lymph vessels, and nerves. The submucosal plexus in this layer regulates the activity of glands and smooth muscles.
Step-by-step explanation:
The submucosa layer of the alimentary canal contains several components, including blood vessels, lymph vessels, and nerves. These blood vessels, both large and small, are responsible for transporting absorbed nutrients. The nerves in the submucosa, along with their associated ganglia, form the submucosal plexus, which regulates activity of glands and smooth muscles.