Costal margin
Encyclopedia
The costal margin, sometimes referred to as the costal arch, is the medial margin formed by the false ribs
False ribs
The false ribs, are the five sets of ribs below the top seven true ribs. A rib is considered to be "false" if it has no direct attachment to the sternum, also known as the breast bone...

 and one true rib -- specifically, from the seventh rib to the tenth rib.
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