Which deep back muscles in the cervical and thoracic region do not receive their blood supply from the deep branch of the costocervical trunk and the posterior intercostal arteries?

• A. Rhomboid Major and Minor
• B. Semispinalis Capitis and Semispinalis Cervicis
• C. Splenius Capitis and Splenius Cervicis
• D. Erector Spinae

Answer: (C)

The blood supply to deep back muscles in the neck and upper thorax comes from two main pathways: the deep cervical artery (a branch from the deep branch of the costocervical trunk) for some deep neck muscles, and the dorsal branches of the posterior intercostal arteries for many thoracic deep muscles. Splenius capitis and splenius cervicis sit a bit more superficially in this region and are supplied primarily by vessels from the external carotid system, especially the occipital artery, with smaller branches that do not rely on the deep cervical trunk’s deep branch or the posterior intercostal arteries in their main supply. That’s why Splenius Capitis and Splenius Cervicis do not receive their primary blood from those two sources.