Ribs 11 and 12 are the floating ribs. These are also known as vertebral ribs or free ribs. They're called "floating" because, unlike the other ribs, they don't attach to the sternum (breastbone) anteriorly. Instead, they terminate in the muscles of the posterior abdominal wall.
Understanding Rib Classification
The human rib cage contains 12 pairs of ribs, categorized into three types based on their connection to the sternum:
- True Ribs (1-7): Directly attached to the sternum via individual costal cartilages.
- False Ribs (8-10): Indirectly connected to the sternum; their costal cartilages are joined to the cartilage of the rib above.
- Floating Ribs (11-12): Lack any anterior connection to the sternum or other ribs.
Function of Floating Ribs
While not directly connected to the sternum, floating ribs still serve important functions:
- Protection: They offer some protection to organs in the lower thorax and upper abdomen, including the kidneys.
- Flexibility: Their lack of anterior attachment allows for greater flexibility in the lower rib cage, aiding in movement.
The flexibility provided by the floating ribs is comparable to the difference between a rigid bridge and a flexible diving board, enabling better movement during various bodily functions. This flexibility also contributes to the overall resilience of the rib cage.
