Posterior branches of thoracic nerves
The medial branches of the posterior divisions of the upper six thoracic nerves run between the semispinalis dorsi and multifidus, which they supply.The medial branches of the lower six are distributed chiefly to the multifidus and longissimus, occasionally they give off filaments to the skin near the middle line.The lateral branches of a variable number of the upper thoracic nerves also give filaments to the skin.The lateral branch of the twelfth thoracic, after sending a filament medialward along the iliac crest, passes downward to the skin of the buttock.This article incorporates text in the public domain from page 923 of the 20th edition of Gray's Anatomy (1918)