Download 09-Posterior triangle2008-11-15 16:318.8 MB

By
Prof. Saeed Abuel Makarem
STERNOCLEIDOMASTOID
Sternocleidomastoid
is a strap muscle.
It descends obliquely
across the side of
the neck.
It forms a prominent
surface landmark.
It divides the side of
the neck into
anterior & posterior
triangles
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TRIANGLES OF THE NECK
The neck is divided into
anterior and
posterior triangles by
sternocleidomastoid
Anterior triangle lies
in front of the
muscle
Posterior triangle lies
behind it.
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Boundaries of the
Posterior triangle:
Anteriorly: posterior
border of sternomastoid
Posteriorly: anterior
border of trapezius
Inferiorly: middle third
of the clavicle.
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OMOHYOID MUSCLE
The omohyoid
muscle has:
 Inferior belly
 Intermediate
tendon
 Superior
belly.
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The inferior belly
of omohyoid
subdivides the
posterior triangle
into:
 a large occipital
triangle above
a small
supraclavicular
triangle below.
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The roof of the triangle is
covered by:
 Skin.
 superficial fascia, which
contains:
 platysma,
 cutaneous branches of
cervical plexus
 External jugular vein
 Investing layer of deep
cervical fascia.
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Running across
the triangle in its
covering:
the cutaneous
branches of
cervical plexus
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The floor of the triangle
is covered by the
prevertebral layer of
deep cervical fascia.
It is formed from below
upward by the:
– Scalenus medius.
– Levator scapulae
– Splenius capitis, &
Semispinalis capitis,
A small part of the
Scalenus anterior may
be present, but it is
usually overlapped and
hidden by the
sternocleidomastoid.
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Parts of Deep
cervical
fascia:
Investing
layer.
Prevertebral
layer.
Pretracheal
layer.
Carotid
sheath.
Notice:
The cutaneous
branches of
cervical plexus
& the external
jugular vein are
contents and in
the same time
they run in the
roof of the
triangle
PLATYSMA MUSCLE
The platysma can
be seen as a sheet
of muscle by
asking the patient
to clench the jaws
firmly.
It extends from
the body of the
mandible
downward over
the clavicle onto
the anterior
thoracic wall.
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Contents of Posterior triangle
Nerves: The main contents are nerves:
 - 3 trunks of the brachial plexus.
 - (4)cutaneous branches of cervical plexus.
(lesser occipital, great auricular, transverse cervical
& supraclavicular nerves.
 - Spinal accessory.
Arteries:
 - 3rd part of subclavian artery.
 - Suprascapular artery.
 - Transverse cervical artery.
 - Occipital artery.
Veins:
 - Subclavian vein.
 - External jugular vein.
+ Muscle: Inferior belly of omohyoid muscle.
BRACHIAL PLEXUS
The brachial
plexus is formed
from the
anterior rami of
the C 5th, 6th,
7th,& 8th &T 1st .
It lies in the
anteroinferior
angle of the
posterior
triangle.
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The roots of the
brachial plexus
enter the posterior
triangle of the
neck through the
interval between
the scalenus
anterior and the
scalenus medius
muscles.
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ACCESSORY NERVE
(SPINAL PART)
The spinal part of
the accessory nerve
enters the posterior
triangle by emerging
from beneath the
middle of the
posterior border of
sternomastoid.
It runs downward
and laterally across
the posterior triangle
on the levator
scapulae muscle,
(dangerous position)
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BRANCHES OF THE CERVICAL PLEXUS
The cervical plexus is
formed by the anterior
rami of C1,C2,C3 &
C4.
Several cutaneous
nerves emerge from
under the middle of
the posterior border
of the sternomastoid
muscle.
They innervate parts
of the skin in the head
and neck region.
N.B.: Block anesthesia
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LESSER OCCIPITAL NERVE
The lesser occipital
nerve is a branch of
C2.
It hooks around the
accessory nerve and
ascends along the
posterior border of the
sternomastoid muscle
It supply the skin over
the lateral part of the
occipital region and
the medial surface of
the auricle.
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GREAT AURICULAR NERVE
The great auricular
nerve is a branch of
C2 & C3.
It ascends across
the sternomastoid
where it divides into
branches that
supply the skin over
the angle of the
mandible, the
parotid gland, and
the auricle.
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TRANSVERSE CERVICAL NERVE
Transverse cervical nerve
of the neck is a branch of
C2 and C3.
It emerges from behind
the middle of the
posterior border of the
sternomastoid.
It passes forward across
that muscle and divides
into branches that supply
the skin on the anterior
and lateral surfaces of the
neck, from the body of
the mandible to the
sternum.
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SUPRACLAVICULAR NERVES
The supraclavicular
nerves are branches
of C3 and C4.
They emerge from
beneath the posterior
border of the
sternocleidomastoid
muscle and descend
across the side of the
neck.
They pass onto the
chest wall and
shoulder region, down
to the level of the
second rib.
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THIRD PART OF THE SUBCLAVIAN ARTERY
The subclavian artery
is divided into three
parts by the scalenus
anterior muscle, which
crosses in front of the
artery.
 First part medial to
scalenus anterior.
 Second part lies
behind the muscle.
 Third part extends
from the lateral border
of the muscle to the
outer border of the first
rib; where, it is
continuous as the
axillary artery.
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The third part of the subclavian artery enters the
anteroinferior angle of the posterior triangle and
disappears behind the middle of the clavicle.
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SUPERFICIAL CERVICAL ARTERY
It is a branch of
the thyrocervical
trunk, of the first
part of the
subclavian artery.
It runs across the
lower part of the
posterior triangle
and disappears
deep to the
trapezius muscle.
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SUPASCAPULAR ARTERY
The suprascapular
artery is also a
branch of the
thyrocervical trunk.
It runs across the
lower part of the
posterior triangle.
It follows the
suprascapular nerve
into the supraspinous
fossa and takes part
in the anastomosis
around the scapula.
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OCCIPITAL ARTERY
It is a branch of the
external carotid
artery.
It enters the posterior
triangle at its superior
angle, appearing
between the
sternomastoid &
trapezius muscles.
Then, it ascends in a
tortuous course over
the back of the scalp,
accompanied by the
greater occipital
nerve.
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EXTERNAL JUGULAR VEIN
The External
jugular vein
begins just
behind the angle
of the mandible
by the union of
the posterior
auricular vein
with the
posterior division
of the
retromandibular
vein.
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TRIBUTARIES
Posterior auricular
vein.
Posterior division of
the retromandibular
vein.
Transverse cervical
vein.
Suprascapular vein.
Anterior jugular vein.
Posterior external
jugular vein, a small
vein that drains the
posterior part of the
scalp and neck and
joins the external
jugular vein about
halfway along its
course.
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