The posterior triangle of the neck contains important structures and is bounded by the sternocleidomastoid muscle anteriorly and the trapezius muscle posteriorly. It contains the subclavian artery, nerves of the brachial plexus and cervical plexus, the external jugular vein and its tributaries. The omohyoid muscle divides it into the larger occipital triangle superiorly and smaller supraclavicular triangle inferiorly. Clinical implications include torticollis resulting from sternocleidomastoid or accessory nerve injury.

1. Posterior Triangle of the
Neck

2. Learning objectives
• At the end of the lecture, the students will be
able to:-
1. Describe posterior triangle of neck.
2. List the contents of posterior triangle of neck.
3. List common applied aspects.

3. The Neck
• The region of the
body that lies
between:
 The lower border
of mandible &
 The suprasternal
notch and the
upper border of
the clavicle

4. Triangles of the Neck

5. Posterior Triangle of the Neck

6. Subdivision of the Posterior Triangle
• Subdivided by the
inferior belly of
omohyoid muscle,
into:
 Large occipital
triangle above
 Small
supraclavicular
triangle below

7. Boundaries of occipital triangle
• Inferior belly of
omohyoid
• Sternomastoid
• trapezius

8. Boundaries of supraclavicular triangle
• Inferior belly of
omohyoid
• Stenomastoid
• Middle-third of clavicle

9. Boundaries
• Anterior: Posterior border
of sternocleidomastoid
• Posterior: Anterior border
of trapezius
• Base: Middle third of
clavicle
• Apex: superior nuchal line
of the occipital bone
between the attachments
of the trapezius and
sternomastoid.

10. Platysma m.
Investing layer of
deep cervical fascia
ROOF OF POSTERIOR TRIANGLE

11. CUTANEOUS BRANCHES OF THE CERVICAL PLEXUS
Lesser occipital n. (C2,3)
Great auricular n.(C2,3)
Transverse cervical n. (C2,3)
Supraclavicular nn. (C3,4)
CERVICAL PLEXUS

12. Muscular Floor of the Posterior
Triangle
From above downward:
 Semispinalis capitis
 Splenius capitis
 Levator scapulae
 Scalenus medius
 Scalenus anterior may
or may not be present

13. Contents
• Arteries:
 Subclavian (3rd part)
 Superficial cervical &
suprascapular
(branches of
thyrocervical trunk, a
branch of 1st part of
subclavian artery
 Occipital, a branch of
external carotid artery

14. • Veins:
• External jugular vein
 Formation
 Termination

15. • Veins:
• External jugular
vein
 Tributaries

16. • Nerves:
 Branches of
cervical plexus
 Spinal part of
accessory nerve
 Brachial plexus

17. Sternocleidomastoid
• Origin: Upper part of
manubrium & medial third of
clavicle
• Insertion: Mastoid process &
lateral part of superior
nuchal line
• Nerve supply: Spinal part of
accessory nerve (motor)

18. Sternocleidomastoid
• Action:
• Both muscles acting
together extend
head at atlanto-
occipital joint, and
flex cervical part of
vertebral column
• Contraction of one
muscle moves the
face to the opposite
side

19. Trapezius
• Origin- medial third of
superior nuchal line,
external occipital
protuberence,
ligamentum nuchae,
spine of seventh
cervical vertebra and
spines of all thoracic
vertebrae.

20. Trapezius
• Insertion- upper fibers
insert into the posterior
aspects of lateral third
of clavicle.
• Middle fibers insert into
medial aspects of
acromian and crest of
the spine of scapula.
• Lower fibers insert into
the crest of scapula.

21. Trapezius
• Action-Upper fibers
elevate the scapula
along with levator
scapulae.
• Middle fibers cause
retraction of scapula
along with rhomboids.
• Lower fibers depresses
and medially rotates the
scapula.

22. Trapezius
• Nerve supply: Spinal
part of accessory nerve
(motor)

23. Omohyoid Muscle
• Two bellies: Superior & Inferior
joined by intermediate tendon
• Attachement: Superior belly to
inferior border of hyoid bone,
Inferior belly to superior border
of scapula & suprascapular
ligament
• The Intermediate tendon lies
deep to sternocleidomastoid
• Nerve supply: Ansa cervicalis
(C1,2,3)
Superior belly
Intermediate
tendon
Inferior belly
Action: Depresses the hyoid bone

24. Clinical Notes
• Torticollis (wry neck):
 Congenital: due to excessive
stretching of
sternocleidomastoid muscle
during labor.
• Injury to spinal part of
accessory nerve
• Injury to brachial plexus
• Injury to nerve to platysma