EXPLAINS ABOIUT THE POSTERIOR TRIANGLE

1. POSTERIOR TRIANGLE
BY
DR . M.MD. MUSTAFA SHARIFF
DEPT OF ANATOMY
SENIOR LECTURER
SRMDC & H

2. POSTERIOR TRIANGLE
• This is a triangular depressed space present above the
middle one third of clavicle and behind the
sternocleidomastoid muscle.

3. POSTERIOR TRIANGLE OFNECK
• Boundaries
• – Infront – posterior border of sternocleidomastoid muscle
• Behind – anterior border of trapezius
• Base – Superior surface of middle 1/3rd of clavicle
• Apex – Superior nuchal line where sternocleidomastoid and
trapezius muscles meet
• Roof – Skin, superficial fascia (platysma), investing layer of
deep cervical fascia

4. STERNOCLEIDOMASTOID MUSCLE (SCM)
Origin:
• Sternal head --- manubrium
• Clavicular head --- medial 1/3 of clavicle
Insertion:
• Mastoid process and lateral ½ of superior nuchal
line

5. Action:
• When muscle of one side contracts, the head is tilted to the
same side and chin is rotated to opposite side.
• When muscles of both side contract the head and neck are
flexed
Nerve supply:
• Spinal part accessory nerve , ventral rami of spinal nerves
C2,C3

6. TRAPEZIUS MUSCLE
Origin:
✓ Superior nuchal line, ext. occipital protuberance, lig.
nuchae, spines of C7 – T12
Insertion:
✓ Lateral 1/3 of clavicle, acromion, spine of scapula
Functions:
✓ Elevation of scapula (sup. fibers),
✓ Depression of scapula (inf. fibers),
✓ Retraction of scapula (middle fibers),
✓ Superior rotation of glenoid fossa of scapula (sup. +
inferior fibers).

7. ROOF OF THE POSTERIOR TRIANGLE
• The ROOF of the
posterior triangle is the
platysma m. and the
investing layer of deep
cervical fascia.
• The platysma is a
muscle of facial
expression and will be
discussed later.
Platysma m.
Investing layer of
deep cervical
fascia

8. Roof is pierced by :
Nerves :
✓ Lesser occipital, Anterior
✓ Great auricular,Superior
✓ Transverse cutaneous nerve of the neck, Posterior
✓ Supraclavicular nerves, Inferior

9. • The FLOOR of
the post.
triangle is the
Splenius capitis
Levator
Scapulae
• Posterior,
middle, and
Anterior
Scalene
muscles.
Muscles of floor
Splenius capitis m.
Levator scapulae m.
Post., mid., &
ant.scalene .m

10. CONTENT OF POSTERIOR TRIANGLE
• The spinal accessory nerve and the lymph nodes are the
true content of posterior triangle and all others are behind
or front of the fascial floor.
• Inferior belly of omohyoid
• Accessory nerve
• Root, trunks of brachial plexus and their branches.
• Nerve to rhomboideus
• Nerve to serratus anterior
• Nerve to subclavius
• Supra clavicular

11. • Greater occipital nerve
• Great auricular nerve
• Lesser occipital nerve
• Transverse cervical nerve
• Supraclavicular nerve
• Third and fourth cervical nerve supplying trapezius
Arteries:
• Occipital artery emerges from the apex.
• Third part of subclavian artery and branches of subclavian
artery.
• Transverse cervical artery

12. Veins:
• External jugular vein and its tributaries.
Lymphoid nodes:
• Supraclavicular lymph nodes are present along the
posterior border of sternomastoid.
• Occipital lymph node

13. CONTENT OF POSTERIOR TRIANGLE

14. SUBDIVISION OF POSTERIOR TRIANGLE
• Inferior belly of omohyoid
muscle
• Occipital triangle
• Supraclavicular triangle
Occipital triangle:
Boundaries
Floor
• semispinalis capitis
• Splenius capitis
• Levator scapulae
• S-medium and post

15. Contents of occipital triangle:
• Spinal part of accessory nerve– C3, C4
• Dorsal scapular nerve (C5)
• Four cutaneous branches
• Lesser occipital nerve (C2)
• Great auricular nerve (C2, C3)
• Transverse cervical of neck (C2, C3)
• Supraclavicular nerve (C3, C4)
• Upper trunk of brachial plexus
• Superficial cervical artery
• Occipital artery (occasional)

16. SUPRACLAVICULAR
TRIANGLE OR
(SUBCLAVIAN TRIANGLE)
Boundaries
Roof :
• Skin
• S/F (platysma)
• investing layer of deep
cervical fascia, pierced by
three diverging branches
of supraclavicular nerve
and external jugular vein

17. Floor
• Outer border of 1st rib
• S. medius (near insertion)
• 1st digitation of serratus anterior.
• Usually serratus anterior overlapped by
sternocleidomastoid muscle.

18. Contents
• Third part of subclavian artery
• Subclavian vein
• Terminal part of external jugular vein
• Trunk of brachial plexus
• Dorsal scapular nerve (C5)
• Long thoracic nerve (C5-C7)
• Nerve to subcalvius (C5)
• Supraclavicular nerve (C3, C4)
• Superficial cervical, Suprascapular, dorsal scapular
arteries
• Posterior inferior group of deep cervical lymph nodes

20. EXTERNAL JUGULAR VEIN
• It lies deep to the platysma.
• It is formed by union of the posterior auricular vein with
the posterior division of retromandibular vein.
• It begins within the parotid gland,
• Cross the sternocleidomastoid obliquely,
• Pierce the antero inferior angle of the roof of the posterior
triangle and into the subclavian vein.

21. • As it pierce the fascia, the margins of the vein get adherent
to the fascia.
• So if the vein gets cut , it cannot close and the air enters
into it and causes air embolism.
• To prevent this , the deep fascia has to be cut.
Its tributaries are
• Posterior external jugular vein.

22. • The transverse cervical vein
• The supra scapular vein
• The anterior jugular vein
• The oblique jugular vein connects the external jugular vein
with the internal jugular vein across the middle one third of
the anterior border of the sternocleidomastoid.

23. CLINICAL ANATOMY
• The most common swelling in the posterior triangle
is due to enlargement of the supraclavicular lymph
nodes.
• A swelling in this region may also be caused by a
lipoma.

24. • Left supraclavicular (Virchow’s) lymph nodes are enlarged
in malignancy of testis, stomach, and other abdominal
organs.
• The pressure in the external jugular vein can be recorded in
the recumbent position.
• It is increased in right side heart failure and in obstruction
of the superior vena cava.
• The retropharyngeal abscess may be expressed in the lower
part of the posterior triangle.

25. REFERENCES
o EXAM-ORINTED ANATOMY SHOUKAT N.KAZI
o TEXT BOOK OF ANATOMY HEAD NECK AND
BRAIN VOL III VISHRAM SINGH
o HEAD & NECK AK DATTA 5TH EDITION
o GRAYS ANATOMY STUDENTS EDITION
o CLINCAL ANATOMY SNELL 8TH EDITION
o CLINICAL ANATOMY MOORE 5TH EDITION
o HEAD & NECK BD CHAURASIA’S 4TH EDITION
o HEAD & NECK DR.AS.MONI