The posterior triangle is an anatomical region of the postero-lateral neck containing several clinically important structures.
Occipital (apex of triangle)
Transverse cervical (From thyrocervical trunk, anterior to anterior scalene)
Suprascapular (From thyrocervical trunk, anterior to anterior scalene)
3rd part of subclavian (deep to prevertebral fascia)
Transverse cervical (accompanying its artery)
Suprascapular (accompanying its artery)
External jugular vein (initially superficial to sternocleidomastoid, it pierces the investing layer near the clavicular head to enter the triangle at its anterior corner)
Muscular & cutaneous branches of cervical plexus (initially deep to prevertebral fascia, they enter posterior triangle before piercing investing layer and coursing superficially)
Lesser & Greater Occipital (near the apex)
Great auricular (deep to mid-SCM, loops around its posterior edge)
Transverse cervical (deep to mid-SCM, loops around its posterior edge)
Suprascapular (deep to mid-SCM, loops around its posterior edge)
Brachial plexus trunks (deep to prevertebral fascia, closely related to subclavian artery)
Spinal accessory root (pierces sternocleidomastoid, giving off branches to it, traverses back across triangle running deep to trapezius)
Suboccipital nodes (at the apex)
Supraclavicular nodes (at the base, inferior to omohyoid)
Whilst some of the structures of the posterior triangle are quite superficial and thus vulnerable to injury (e.g.
external jugular vein), many of the key structures (e.g. – subclavian artery, brachial plexus trunks) lie deep to the
prevertebral fascia where they are relatively safe.
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CN XI / Subclavian artery / EJV / Brachial plexus trunks