Paired ribs are attached to each thoracic vertebra against which they move in breathing. Each rib is attached ventrally either to the sternum or to the rib in front by cartilage to form the rib cage that protects the heart and lungs. In dogs one pair of ribs is not attached ventrally at all. They are called floating ribs (see diagram 6.5). Birds have a large expanded sternum called the keel to which the flight muscles (the ‘breast” meat of a roast chicken) are attached.
Diagram 6.5 - The rib