There are twelve pairs of ribs which are separated by the intercostal spaces. The upper 7 ribs show increase on length progressively while the lower 5 ribs show gradual decrease in length.
The ribs could be:
true the first 7 ribs that attach to the sternum directly
false from 8th to 10th that attach to the sternum through costal cartilage
floating the 11th and 12th with no articulation to the sternum
The CT scan is derived from the file STS_040
The 3D bone model created from this scan can be reviewed at: