Superficial Musculature of the Posterior Neck. Reflection of the posteroinferior scalp and skin and superficial fascia of the neck reveals several neck muscles. Most superficially in this view are the trapezius muscles arising from the medial third of the superior nuchal line, the external occipital protuberance, and spinous processes of cervical vertebrae via the nuchal ligament. Laterally, upper fibers of the sternocleidomastoid muscles insert into the lateral half of the superior nuchal line and mastoid process. The gap between the trapezius and sternocleidomastoid muscles is filled by the splenius capitis muscle. Near the midline, deep to the superior edges of the trapezius muscles are the longitudinal fibers of the semispinalis capitis muscle. (Image courtesy of PA Rubino)