Home ยป Out of the following, which is a major secretory layer of the GI tract? Excretory System MCQs Out of the following, which is a major secretory layer of the GI tract? January 24, 2022 4 Views Q. Out of the following, which is a major secretory layer of the GI tract? A. Mucosa B. Submucosa C. Muscularis D. Serosa Answer: Mucosa