external intercostal (muscle)

ex·ter·nal in·ter·cos·tal (muscle)

[TA]
flat muscle of thorax arising from lower border of one rib and passing obliquely downward and forward to be inserted into the upper border of rib below; action, contract during inspiration to elevate ribs; also to maintain tension in the intercostal spaces to resist inward movement during inspiration; nerve supply, intercostal.
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