Rib 7 (left) — true rib

Function

The last true rib and the longest of them all — its cartilage tips the costal margin that shields the upper abdominal organs.

Landmarks

• Costal groove
• Angle
• Costal margin contribution

Articulations (joints)

• T6–T7 vertebrae
• Sternum via seventh costal cartilage

Clinical relevance

Chest drains are placed no lower than the fifth intercostal space in the mid-axillary line — lower insertion risks puncturing the diaphragm, liver or spleen.