3; Mark Sloan (Eric Dane), head of plastic surgery; Callie Torres (Sara Ramirez), a resident who later becomes head of orthopedic surgery and leaves Seattle for New York at the end of the 12th season; Erica Hahn (Brooke Smith), as head of cardiothoracic surgery, who leaves Seattle Grace in season 5 after a disagreement with Torres, with whom she shared a brief relationship; Owen Hunt (Kevin McKidd), as head of trauma who later marries and divorces Yang; Arizona Robbins (Jessica Capshaw), as head of pediatric surgery, and later head of maternal / fetal surgery who marries Torres; Teddy Altman (Kim Raver), as head of cardiothoracic surgery who departs at the end of season 8 but returns in season 14; and Amelia Shepherd (Caterina Scorsone), Derek's sister, who is hired to replace him as head of neurosurgery. Lexie Grey (Chyler Leigh), Meredith's paternal half-sister, joins the residency program in season 4 until her death with her love-interest Mark Sloan in the plane crash at the end of season 8, after which Seattle Grace is renamed Grey Sloan Memorial Hospital in their memory. Former Mercy-West residents April Kepner (Sarah Drew) and Jackson Avery (Jesse Williams) join Seattle Grace following an administrative merger in season 6. Other additions include Leah Murphy (Tessa Ferrer), who departs at the end of season 10 but returns during season 13; Shane Ross (Gaius Charles), who leaves with Yang for Zurich, Switzerland, in the season 10 finale; Stephanie Edwards (Jerrika Hinton), who resigns at the end of season 13; Jo Wilson (Camilla Luddington), who marries Karev; Andrew DeLuca (Giacomo Gianniotti), the former love interest of Meredith's maternal half sister Maggie Pierce (Kelly McCreary) who also serves as head of cardiothoracic surgery; and Ben Warren (Jason George), an anesthesiologist turned resident turned firefighter who marries Bailey. Season 11 sees the death of Derek Shepherd, and in season 12, attending cardiovascular surgeon Nathan Riggs (Martin Henderson) joins the show. In the early episodes of season 14, Thomas Koracick (Greg Germann), an attending neurosurgeon, begins making appearances and Riggs leaves the series to start a life with Owen's long-lost sister Megan (Abigail Spencer); by the season finale, Robbins, Kepner and Warren also depart the show. Midway through the 16th season, Cormac Hayes (Richard Flood) becomes the new Chief of Pediatric Surgery and Karev made his final appearance on the series. During the 17th season, DeLuca is stabbed while chasing a child