In which gastrointestinal tunic are general receptors located?

The answer is the sub-mucosa layer. This layer is highly inundated with nerve supply that controls the secretions (hormones, mucus, and enzymes) of glands in the mucosa layer. It is the depolarization of these chemoreceptors and pressoreceptors that activate responses such as salivation.  This layer also contains the lymphatic and blood vessels that nourish the GI cells.

answer:

sequence 1- deletion

                  2- duplication

                  3- insertion

                  4- substitute

                  5- inversion