[Plate 129, Autonomic Nerves in Neck]page 20
page 21Sternocleidomastoid (SCM) on each side of neck divides each side into two triangles:
Anterior
Posterior
Facilitates description of anatomy of the neck
Posterior Triangle
Boundaries
Posterior-anterior border of trapezius
Anterior-posterior border of SCM
Inferior-medial third clavicle
Roof-investing layer of deep cervical fascia
Floor-muscles
Muscles of the floor
Splenius capitis
Levator scapulae
Middle scalene
Posterior scalene
Vessels in triangle
External jugular vein
Subclavian vein
Third part of subclavian artery
Transverse cervical artery (from thyrocervical trunk)
Suprascapular artery (from thyrocervical trunk)
Occipital artery (from external carotid)
Nerves in the triangle
Accessory nerve (cranial nerve [CN] XI)
Ventral rami (roots) of brachial plexus
Cutaneous branches of cervical plexus
Suprascapular nerve
Phrenic nerve
Subdivided by inferior belly of omohyoid