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.
Pork ribs
Baby back ribs (also back ribs or loin ribs) are taken from the top of the rib cage between the spine and the spare ribs, below the loin muscle. They have meat between the bones and on top of the bones, and are shorter, curved, and sometimes meatier than spare ribs. The rack is shorter at one end, due to the natural tapering of a pig's rib cage. The shortest bones are typically only about and the longest is usually about , depending on the size of the hog. A pig side has 15 to 16 ribs (depending on the breed), but usually two or three are left on the shoulder when it is separated from the loin. So, a rack of back ribs contains a minimum of eight ribs (some may be trimmed if damaged), but can include up to 13 ribs, depending on how it has been prepared by the butcher. A typical commercial rack has 10–13 bones. If fewer than 10 bones are present, butchers call them "cheater racks".Rib tips are short, meaty sections of rib attached to the lower end of the spare ribs, between the ribs and the sternum. Unlike back ribs or spare ribs, the structure of the rib is provided by dense costal cartilage, not bone. Rib tips are cut away from the spare ribs when preparing St. Louis style spare ribs.