Rib cage
The rib cage is the arrangement of ribs attached to the vertebral column and sternum in the thorax of most vertebrates, that encloses and protects the heart and lungs. In humans, the rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the shoulder girdle to form the core part of the human skeleton. A typical human rib cage consists of 24 ribs in 12 pairs, the sternum and xiphoid process, the costal cartilages, and the 12 thoracic vertebrae.
Short ribs
The "serratus ventralis" muscle defines the area in the beef carcass from where short ribs come, and is the preferred muscle tissue for short ribs. This muscle originates near the second rib, and covers most of the rib cage. In the chuck area (second through fifth ribs), the muscle is much thicker. Moving toward the rump, the "serratus ventralis" becomes less dense, and may not cover the entire rib. Outside of the chuck, the "serratus ventralis" covers the entire rib with a degree of thickness only in the plate area. Over ribs nine through 12, the "serratus ventralis" is too thin to properly create a true short rib, and meat here is usually turned into a "Royal short rib" or else stripped from the bone and used for ground beef.