Expansion
7 true ribs, 3 false ribs, 2 floating ribs
Mnemonic
The 7, 3, 2 rule for costal attachment:
- 7 - ribs 1 to 7 are true ribs, attaching directly to the sternum by their own costal cartilage
- 3 - ribs 8, 9 and 10 are false ribs, joining the cartilage of the rib above
- 2 - ribs 11 and 12 are floating, with no anterior attachment at all
7 plus 3 plus 2 gives the 12 ribs.
The floating ribs have no costal cartilage and only a single articular facet, and their free tips are why renal approaches through the loin risk pleural injury at the 12th rib.
Expansion
- 7 true ribs
- 3 false ribs
- 2 floating ribs