internal 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.