Final answer:
The submucosa system is the connective tissue layer supporting the GI tract and it includes the submucosal plexus and blood and lymphatic vessels.
Step-by-step explanation:
The connective tissue system that supports the gastrointestinal tract and supplies it with blood, lymph, and nerves is known as the submucosa system. This layer is found beneath the mucosa and is comprised of dense connective tissue. It forms a connection between the mucosa and the muscularis, housing blood and lymphatic vessels that transport absorbed nutrients.
Additionally, the submucosa contains glands that release digestive secretions and a dense branching network of nerves called the submucosal plexus. The enteric nervous system, a division of the autonomic nervous system, is directly involved in controlling digestive function through myenteric plexuses located in the walls of the digestive organs.