Final answer:
A layer of connective tissue supports the submucosa, situated between the muscularis mucosae and muscularis externa, containing blood and lymphatic vessels, glands, and the submucosal plexus for nutrient transport and digestive regulation.
Step-by-step explanation:
The components of the submucosa are supported by a layer of connective tissue located between the muscularis mucosae and muscularis externa. This layer includes blood and lymphatic vessels which are essential for transporting absorbed nutrients throughout the body.
Additionally, the submucosa houses submucosal glands that release digestive secretions and a dense network of nerves known as the submucosal plexus, which is crucial for regulating the activity of both glands and smooth muscle in the digestive tract.