What is extra Mucosal Gland?
There is no such term as extra mucosal gland.
Mucosal glands are the glands that secrete mucus which protects the epithelial cells of various major organs.
For eg- Brunner’s gland is a tubular gland present in the duodenum part of alimentary canal. The main function of this gland is to produce mucus rich alkaline secretion to protect the duodenum from the acidic content of food matter coming from the stomach. This secretion not only makes the matter alkaline but also lubricates the walls of intestine.