serratus posterior inferior
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Related to serratus posterior inferior: Quadratus lumborum
ser·ra·tus posterior inferior(sə-rā′təs)
A muscle with origin from the two lower thoracic and two upper lumbar vertebrae, with insertion into the last four ribs, with nerve supply from the ninth to the twelfth intercostal nerves, and whose action draws the lower ribs backward and downward.