Why the acid in stomach does not digest the stomach itself?

a) The stomach walls have a lining that contains epithelial cells that secrete a protective layer of mucous and bicarbonate.
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b) It sticks to the walls of the stomach to provide a physical barrier against the acid in the stomach.
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c) When the cells come into contact with acid, they secrete bicarbonate which is highly alkaline and highly effective in neutralizing the acid.
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