Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Jejunal atresia ?
    ### Response:
    Jejunal atresia is a birth defect that occurs when the membrane that attaches the small intestines to the abdominal wall (called the mesentery) is partially or completely absent. As a result, a portion of the small intestines (the jejunum) twists around an artery that supplies blood to the colon (the marginal artery).
    