Expansion
Lung borders cross ribs 6, 8 and 10; pleural borders cross ribs 8, 10 and 12
Expansion
Counting down at three vertical lines:
| Line | Lung border | Pleural border |
|---|---|---|
| Mid-clavicular | Rib 6 | Rib 8 |
| Mid-axillary | Rib 8 | Rib 10 |
| Paravertebral | Rib 10 | Rib 12 |
So the sequence for the lung is 6, 8, 10 and for the pleura 8, 10, 12, always two ribs lower.
That two-rib gap is the costodiaphragmatic recess. It is also a warning: a needle placed below the lung border is still within the pleural cavity, and one placed below the pleural border risks the liver on the right or the spleen on the left.