GREY'S ANATOMY - "Support System" - A devastated Cristina presses Owen to confess the intimate details of his affair; Mark takes his new authority very seriously when he steps in as chief for the day and butts heads with Richard over a patient's liver transplant; and Callie deems Meredith ready for the boards, while the rest of the residents continue to stress about the exam. Meanwhile, Callie, Arizona and Bailey plan a much needed ladies night for Teddy, on "Grey's Anatomy," THURSDAY, APRIL 12 (10:01-11:00 p.m., ET) on the ABC Television Network. (ABC/RANDY HOLMES) CHANDRA WILSON, JESSICA CAPSHAW