Rib
Ribs are classed as flat bones which usually have a protective role in the body. Humans have 24 ribs, in 12 pairs. All are attached at the back to the thoracic vertebrae, and are numbered from 1–12 according to the vertebrae they attach to. The first rib is attached to thoracic vertebra 1 (T1). At the front of the body most of the ribs are joined by costal cartilages to the sternum. The ribs connect to the vertebrae with two joints, the costovertebral joints.
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.