Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Hiatal Hernia ?
    ### Response:
    A hiatal hernia is a condition in which the upper part of the stomach bulges through an opening in the diaphragm. The diaphragm is the muscle wall that separates the stomach from the chest. The diaphragm helps keep acid from coming up into the esophagus. When you have a hiatal hernia, it's easier for the acid to come up.
    