Question

what will happen if mucus is not secreted by the gastric glands

Answer 1

if mucus is not secreted by gastric gland then there will be no protected lining to protect our elementary Canal from highly acidic nature of digestive juices produced hence ulcers also will get developed and we will not able to survive

Answer 2

then the HCl will cause damage to the linings of stomach as the mucous prevents the acid to damage the linings.