internal intercostal muscle
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Related to internal intercostal muscle: External intercostal muscles, innermost intercostal muscle
in·ter·nal in·ter·cos·tal mus·cle(in-tĕr'năl in'tĕr-kos'tăl mŭs'ĕl)
Each arises from lower border of rib and passes obliquely downward and backward to be inserted into upper border of rib below; action, contract during expiration, also maintain tension in the intercostal spaces to resist mediolateral movement; nerve supply, intercostal.