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Posterior Triangle
Nainika Menon
Borders
• Anterior: sternocleidomastoid mm (SCM) –
posterior border
• Posterior: trapezius mm – anterior border
• Base: Middle 1/3 clavicle
• Apex: Superior nuchal line (occipital bone)
• Roof: Investing layer of fascia
• Floor (sup inf): splenius capitis, levator scapulae,
posterior/middle/anterior scalene mm (all covered by
prevertebral layer of fascia)
POSTERIOR TRIANGLE
Occipital Triangle
Inferior belly
of omohyoid
Omoclavicular Triangle
- (Part of) external jugular vv
- Posterior branches
(cutaneous) of cervical plexus
- 3rd part of subclavian aa
- Spinal accessory nn (CN 11)
- Part of subclavian vv
- Brachial plexus (trunks)
- Suprascapular aa
- Cervicodorsal trunk
- Supraclavicular lymph
nodes
- Cervical lymph nodes
External Jugular vv
• Superficial
• Retromandibular vv (posterior branch)
+ Posterior auricular vv
= external jugular vv (angle of mandible)
• Drains into subclavian vv
(not to be confused with: IJV + subclavian vv -->
brachiocephalic vv)
Spinal Accessory nn (CN 11)
• Deep to SCM across posterior triangle over
levator scapulae deep to trapezius
• Clinical note: can be damaged
– Difficulty turning head to side (with resistance)
SCM
– Shoulders droop/cannot raise and retract
shoulder/cannot raise arm above horizontal
Trapezius
Trapezius
• Origin: superior nuchal line/external occipital protuberance +
ligamentum nuchae + vertebrae C7-T12 (spinous processes)
• Insertion: lateral 1/3 clavicle + acromion + spine of scapula
• Innervation: CN 11
• Action:
– Superior part (descending) – maintains shoulders
– Middle part – retraction of scapula
– Inferior part (ascending) – lowers shoulders
– Bilaterally extension of neck
– Unilaterally lateral flexion to the side that is
contracting
– General: elevation, retraction, rotation of scapula
Arteries
• Subclavian aa thyrocervical trunk (2nd
branch) cervicodorsal trunk (aka transverse
cervical aa)
• Cervicodorsal trunk/subclavian aa
suprascapular aa
• 3rd part of subclavian aa (blood supply to
upper limb) – subclavian vv is anteroinferior
0
Lymphatics
• Superficial regions of neck superficial
cervical lymph nodes inferior deep cervical
lymph nodes supraclavicular lymph nodes
• Deep cervical lymph nodes run along IJV
Cutaneous Branches of Cervical
Plexus
• Lesser occipital nn (C2)
• Great auricular nn (C2,3)
• Transverse cervical nn (C2,3)
• Supraclavicular nn (C3,4)
Thank You!
References
• Information from:
MOORE, Keith L., Anne AGUR, Arthur DALLEY. Essential Clinical
Anatomy. 4th ed. Baltimore: Lippincott Williams & Wilkins, 2011
DRAKE, Richard L., A. Wayne VOGL, Adam W. M. MITCHELL.
Gray’s Anatomy for Students. 2nd ed. Philadelphia: Churchill
Livingstone, 2010
• Images from:
DRAKE, Richard L., A. Wayne VOGL, Adam W. M. MITCHELL.
Gray’s Anatomy for Students. 2nd ed. Philadelphia: Churchill
Livingstone, 2010