Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Gastritis ?
    ### Response:
    Gastritis is a condition in which the stomachliningknown as the mucosais inflamed, or swollen. The stomach lining contains glands that produce stomach acid and an enzyme called pepsin. The stomach acid breaks down food and pepsin digests protein. A thick layer of mucus coats the stomach lining and helps prevent the acidic digestive juice from dissolving the stomach tissue.
    