erector spinae m., consisting of iliocostalis m., longissimus m., spinalis m. :
large block of epaxial muscle major spine extensor and a lateral flexor. Note that epaxial mm. names refer more to patterns of attachment than to individual muscles, e.g., longissimus thoracis, cervicis, capitis. Erector spinae mm. refers to the following three components; iliocostalis most lateral, attached to ribs, longissimus attached to transverse processes, spinalis thin and most medial, attached to spinous processes.