Download 09-posterior triangle

TRIANGLES OF THE NECK
The neck is 
divided by the
Sternomastoid
muscle into two
triangles :
Anterior (in 
front).
Posterior 
(behind).
STERNOCLEIDOMASTOID
Origin : 
A. Sternal head: 
Tendinous. 
It arises from the 
upper part of the
manubrium.
B. Clavicular head: 
Fleshy . 
From the medial third 
of the upper surface of
the clavicle.
STERNOCLEIDOMASTOID
Insertion : 
Mastoid process. 
Lateral part of the 
superior nuchal line.
Nerve supply : 
Spinal part of 
acessory.
Proprioceptive (C2 
&3)
STERNOCLEIDOMASTOID
Action : 
Both muscles flex the 
cervical vertebrae and
extend the atlantooccipital joint (as in
praying).
One muscle : pulls the 
mastoid process to the
same side so the face
looks upward to the
opposite side.
POSTERIOR TRIANGLE
Boundaries :
Anterior: posterior
border of
sternomastoid.
Posterior: 
Anterior border of
trapezius.

BOUNDARIES
Inferior: 
Middle third of 
the clavicle.
Superior (Apex) 
It is the meeting 
of the
sternomastoid
and trapezius.
ROOF
It is covered by the
skin, superficial
fascia, platysma
and the
Investing layer of 
the deep cervical
fascia.

INVESTING LAYER:
It completely 
encloses the neck.
It splits to enclose 
the
sternocleidomastoid
and trapezius
muscles.
It roofs the anterior
and posterior
triangles of the
neck.

FLOOR
It is muscular. 
It is formed from 
above downward by
the following
muscles :
Semispinalis capitis.
Splenius capitis. 
Levator scapulae. 
Scalenus medius. 

FLOOR
A small part of 
scalenus
anterior (may)
be present
It is covered by 
the prevertebral
fascia.
PREVERTEBRAL FASCIA:
It covers the 
prevertebral muscles.
It surrounds the 
subclavian artery and
the brachial plexus and
forms the axillary
sheath.
DEEP CERVICAL FASCIA
The investing and 
the prevertebral
layers are attached
posteriorly to the
ligamentum
nuchae.
SUBDIVISIONS
The triangle is 
divided by the
inferior belly of
omohyoid into:
1. large occipital
triangle above.
2.small
supraclavicular
triangle below.

CONTENTS
(1) Arteries : 
3rd part of 
subclavian
artery.
Suprascapular.
Transverse 
cervical.
Occipital. 

CONTENTS
(2) Veins : 
External jugular
vein and its
tributaries.
Subclavian vein.


CONTENTS
(3) Nerves : 
Brachial plexus.
Spinal part of 
acessory nerve.
Branches of the
cervical plexus.


SUBCLAVIAN ARTERY
The subclavian 
artery is divided by
the scalenus
anterior into three
parts :
First : extends from
its origin to the
medial border of the
muscle.
Second : behind the
muscle.


3rd PART OF SUBCLAVIAN
ARTERY
It extends from the
lateral border of
scalenus anterior to
the outer border of
the first rib.
It lies in the 
anteroinferior angle
of the posterior
triangle.

3rd PART OF SUBCLAVIAN
ARTERY
Usually it has no
branches in the
posterior
triangle.
It is 
comparatively
superficial and
its pulsations can
be felt.

RELATIONS
Anterior : 
1.Sternomastoid. 
2. Skin and fascia. 
3. clavicle. 
Veins anterior : 
A. External jugular 
vein (crossing).
B. Subclavian vein 
(below).
RELATIONS
Posterior : 
Lower trunk of the
brachial plexus.
Scalenus medius. 

RELATIONS
Superior : 
Middle and Upper
trunks of the
plexus.
Inferior : 
Upper surface of
the first rib.


SUPERFICIAL CERVICAL &
SUPRASCAPULAR
Both arise from the 
thyrocervical trunk
from the 1st part of
the subclavian artery.
They are in the lower
part of the posterior
triangle

SUPERFICIAL CERVICAL &
SUPRASCAPULAR
The superficial 
cervical passes deep
to trapezius.
Suprascapular 
accompanies its
nerve and shares in
the anastomoses
around the scapula.
OCCIPITAL ARTERY
It arises from the 
external carotid artery.
It appears at the apex 
of the posterior
triangle.
It has a tortuous course
over the back of the
scalp.
It is accompanied by 
the greater occipital
nerve.

EXTERNAL JUGULAR VEIN
It is an important 
superficial vein.
It is formed behind 
the angle of the
mandible by the
union of two veins :
Posterior auricular +
Posterior division of
Retromandibular.

EXTERNAL JUGULAR VEIN
Course : 
It descends 
obliquely over the
sternomastoid.
It pierces the deep
fascia above the
clavicle.
Termination : 
It drains into the 
subclavian vein.

EXTERNAL JUGULAR VEIN
Tributaries : 
1. Posterior 
auricular.
2. Posterior division
of retromandibular
vein.
3. Anterior jugular


EXTERNAL JUGULAR VEIN
4. Transverse 
cervical.
5. Suprascapular.
6. Posterior 
external jugular.

ANTERIOR JUGULAR VEIN
It is formed by the 
union of small veins
below the chin.
The veins of the two 
sides unite to form
a transverse arch
(jugular arch).
SUBCLAVIAN VEIN
It lies on the upper 
surface of the first rib.
It is in front and 
below the 3rd part of
the subclavian artery.
Usually it is not one of
the contents of the
posterior triangle.

NERVES (1) Brachial plexus)
(a) Roots : 
They enter the 
triangle through
the interval
between scaleni
anterior and
medius.
BRACHIALPLEXUS
B. Trunks : 
Upper, middle and
lower.
C. Cords : 
They leave the 
posterior triangle
by passing deep to
the clavicle.

(2) BRANCHES OF CERVICAL
PLEXUS
1. Lesser occipital 
nerve (C2).
It hooks around the 
acessory nerve.
It ascends along the 
posterior border of
sternomastoid.
It supplies skin over 
the medial auricle and
the mastoid region.

BRANCHES OF CERVICAL
PLEXUS
2. Great auricular 
nerve (C2 &3)
It supplies the skin 
over the angle of the
mandible.
Both surfaces of the 
auricle and the
parotid region of
face.
BRANCHES OF CERVICAL
PLEXUS
3. Transverse 
cutaneous nerve
(C2,3)
It emerges behind the 
middle of posterior
border of
sternomastoid.
It divides into branches 
which supply the skin
over the anterior and
lateral surfaces of the
neck.
BRANCHES OF CERVICAL
PLEXUS
4. Supraclavicular
nerves (C3 & 4) :
They emerge 
behind the
posterior border of
sternomastoid.

BRANCHES OF CERVICAL
PLEXUS
They divide into : 
A. Medial : 
Crosses the medial end
of the clavicle and
supplies the skin as far
as the median plane.
B. Intermediate : 
It crosses the middle of
the scapula and
supplies the skin over
the chest.


BRANCHES OF CERVICAL
PLEXUS
C. Lateral : 
It crosses the lateral 
end of the clavicle.
It supplies the skin 
over the upper half of
the deltoid.
It supplies the 
posterior part as far as
the spine of the
scapula.
(3) SPINAL PART OF ACESSORY
NERVE
It emerges from 
beneath the posterior
border of
sternocleidomastoid.
It lies on the levator 
scapulae.
It leaves the triangle by
passing deep to anterior
border of trapezius.
It supplies both 
muscles.

(3) SPINAL PART OF ACESSORY
NERVE
The nerve has a 
relatively superficial
position.
It is related to the 
superficial cervical
lymph nodes.
It is accompanied by
the ventral rami of (C
3 & 4).

INJURY TO ACESSORY
NERVE(SPINAL PART)
The nerve is easily 
injured.
Its injury causes 
paralysis to trapezius.
The muscle will show 
wasting.
The shoulder will drop. 
The patient will have 
difficulty in elevating the
arm above the head.