Corpus3D

Spine

Tenth rib in the midaxillary line

Costa X

How to find it
Draw a vertical line down from the middle of the axilla. Count the ribs downward: the lowest one you can still follow there as a continuous arch to the costal margin is the one you want.
What you use it for
A fixed landmark for organ projection: the lower pole of the left kidney and the spleen lie at this level. Also the boundary below which the eleventh and twelfth ribs end freely.
On the bone
Rib (10th)
Body region
Spine