Atypical ribs

Last revised by Raymond Chieng on 03 Dec 2022

Owing to their features, the first, eleventh and twelfth ribs are considered atypical ribs. Some authors also include the second and tenth ribs as atypical. Atypical features are summarized below:

  • first rib

    • strongest, broadest and most curved

    • tubercle at the inner border marks the attachment of scalenus anterior muscle 2

    • subclavius is attached to sternal end of the rib

    • has grooves for the subclavian vein, artery, and brachial plexus

      • the subclavian vein (anterior) is separated from subclavian artery (posterior) by scalene tubercle 2

      • brachial plexus lies posterior to the subclavian artery 2

    • single facet articulation with T1 vertebrae 2

  • second rib

    • less curved and two times lengthier than the first rib 2

    • anterior surface marks one of the origins of the serratus anterior muscle

    • tubercle on its external border marks the attachment of second head of the scalenus anterior muscle 2

  • tenth rib

    • differs from other typical ribs by a single facet articulation with the T10 vertebrae 2

  • eleventh and twelfth ribs

    • shorter (no neck or tubercles) and do not attach to the sternum

    • single facet articulation with the same-level vertebrae

    • twelfth rib has no subcoastal groove 2

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Cases and figures

  • Figure 1: atypical ribs - 1st (Gray's illustration)
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  • Figure 2: atypical ribs - 2nd (Gray's illustration)
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  • Figure 3: Atypical ribs - 10, 11, 12 (Gray's illustration)
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