Keel (bird anatomy) Keel (bird anatomy) A keel or carina (plural carinae) in bird anatomy is an extension of the sternum (breastbone) which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight. Keels do not exist on all birds; in particular, some flightless birds lack a keel structure. Historically, the presence or absence of a pronounced keel structure was used as a broad classification of birds into two orders: Carinatae (from "carina", "keel"), having a pronounced
What a Difference a Day Makes (Grey's Anatomy) What a Difference a Day Makes (Grey's Anatomy) "What a Difference a Day Makes" is the twenty-second episode of the fifth season of the American television medical drama, "Grey's Anatomy" and the show's 100th episode overall. Written by series creator Shonda Rhimes and directed by Rob Corn, the episode was originally broadcast on the American Broadcasting Company (ABC) in the United States on May 7, 2009. "Grey's Anatomy" centers around a group of young doctors in training. In this episode, a wedding takes place. The episode received generally favorable reviews. The initial airing was viewed by 15.326 million people and