CERVICAL
TRIANGLES
As you dissect
in this region,
you will see
many more
structures than
are visible in
this picture.
So, this is a
region where it
is VERY
important for
you to know
where vessels
and nerves are
BEFORE you
begin cutting
and cleaning.
Review the
anatomy of the
VEINS of this
region.
Superficial temporal v.
Facial v.
Internal jugular v.
External jugular v.
Cephalic v.
Axillary v.
Subclavian v.
Brachiocephalic v.
Superior
vena cava
Anterior
jugular v.
Review the
anatomy of
the
ARTERIES
of this
region.
Occipital a.
Superficial temporal a.
Transverse facial a.
Internal carotid a.
External carotid a.
Superficial cervical a.
Facial a.
Suprascapular a.
Anterior circumflex
humeral a.
Superior
thyroid a.
Axillary a.
Thoracoacromial a.
Thyrocervical
trunk
Lateral thoracic a.
Subclavian a.
AND, where are
those all
important
phrenic and
vagus nerves
that we want to
SAVE?
To best observe
these
structures, you
need to cut or
reflect the
internal jugular
vein which allows
you a good view
of the common
carotid artery
and the anterior
scalene m..
So, once the internal jugular
vein is reflected, you will be
able to see these nerves.
Internal jugular v.
Vagus n. – this nerve
literally lies within the
carotid sheath.
Phrenic n. – this nerve
lies on the anterior
surface of the anterior
scalene m..
CERVICAL TRIANGLE
SKIN INCISIONS
1. Make a VERY, VERY
SUPERFICIAL incision in
the midline of the neck
from the tip of the chin
to the suprasternal
notch.
2. Make a VERY, VERY
SUPERFICIAL incision
along the clavicle from
its medial end to a point
that is about 3 cm.
beyond the acromion
process.
3. Make a VERY, VERY
SUPERFICIAL incision
just anterior to the
anterior border of the
sternocleidomastoid m..
4. Reflect skin laterally.
Identify the
platysma m..
Reflect the platysma m. superiorly towards the
mandible. Be VERY careful to not damage the
underlying attached structures.
With the platysma m. reflected, note the vessels that you should observe in
the anterior cervical triangle.
External
jugular vein
Anterior
jugular
veins
Identify the boundaries of
the posterior cervical
triangle.
Anteriorly, it is bounded
by the posterior edge of
the sternocleidomastoid
m..
Posteriorly, it is bounded
by the anterior edge of
trapezius m..
Inferiorly, it is bounded
by the clavicle.
External
jugular vein
Great
auricular
nerve
You should be able to identify some of the most superficial structures in this
region, such as the largest cutaneous nerve of the cervical plexus, the great
auricular nerve (C2, C3). It crosses the surface of the superior part of the
sternocleidomastoid muscle and lies adjacent to the external jugular vein (which
drains into the subclavian vein).
Transverse
cervical
nerve
Erb’s point
The transverse cervical nerve (C2, C3) crosses the sternocleidomastoid m.
transversely.
These cervical nerves emerge from a region that is called Erb’s point.
Find the spinal accessory
nerve (CN XI) passing deep
to the sternocleidomastoid
muscle.
It crosses the posterior
triangle.
This nerve is responsible for
innervating the
sternocleidomastoid and
trapezius mm..
Recall that you make
mention of this nerve when
you teach the cranial
nerves.
To examine the structures at the base of the posterior triangle, it may be
necessary to cut through the clavicle just lateral to the attachment of the
sternocleidomastoid muscle.
Only perform this bone cut if you have been told to do so!!!!
Superior belly of
the omohyoid m.
The two bellies of the
omohyoid m. are connected
by an intermuscular tendon,
that is held by connective
tissue to the anterior
surface of the internal
jugular vein to prevent the
vein from collapsing under
negative pressure.
Inferior
belly of the
omohyoid m.
Suprascapular a.
Anterior scalene m.
Transverse cervical a.
At this point you should clearly see the anterior scalene m. and two arteries
that overlie it. Even though we do not typically show these two arteries during
lab, we do show the vessel from which they originate, the thyrocervical trunk.
Phrenic n.
Anterior scalene m.
As you clean the anterior scalene m., PLEASE do NOT damage the phrenic n.
which should be found running vertically along its medial border. The fibers of
this nerve are generally derived from C3, 4, and 5. Recall that each phrenic
n. innervates one- half of the diaphragm.
Middle scalene m.
Splenius capitus m.
Levator scapulae m.
Besides the anterior scalene m., you should be able to clearly see some of the
other “prevertebral muscles” that form the floor of this posterior triangle.
Anterior scalene m.
Middle scalene m.
Trunks of the
brachial plexus
Between the anterior scalene and the middle scalene mm., identify and clean
the trunks of the brachial plexus.
So, you should now have a posterior cervical triangle with the muscles shown in
this picture cleaned of their overlying fascia.
Splenius capitus m.
Middle scalene m.
Levator scapulae m.
Anterior scalene m.
Posterior scalene m.
Trunks of the
brachial plexus
Inferior
belly of the
omohyoid m.
Notice some of the nerves that are found in this region.
Dorsal scapular
nerve that
innervates the
rhomboid and
levator scapulae
mm.
Long thoracic nerve
that innervates the
serratus anterior m.
Suprascapular nerve
Trunks of the
brachial plexus
that innervates the
supraspinatus and
infraspinatus mm.
Now, continue your dissection by finding and cleaning the contents of the
anterior cervical triangles. Note the boundaries of each of these triangles are
the sternocleidomastoid m., the midline of the neck, and the mandible.
Hyoid bone
Within these triangles is
found the hyoid bone at
the angle between the
floor of the mouth and
the superior neck.
Four ribbon-like (straplike) muscles are found on
each side descending from
the hyoid bone or the
thyroid cartilage. As a
group, they are called the
infrahyoid mm..
Recall that their names
basically describe their
attachments.
Superior belly of the
omohyoid m.
Sternohyoid m.
Thyrohyoid m.
Sternothyroid m.
If these infrahyoid
muscles are retracted
laterally, you can observe
some other important
structures.
Thyroid cartilage
Cricoid cartilage
First tracheal ring
Cricothyroid membrane
Cricothyroid muscles
Incisions through the cricothyroid
membrane are a way to quickly access
the airway inferior to the vocal cords
(cricothyrotomy). structures.
http://www.aic.cuhk.edu.hk/web8/dilational_cricothyrotomy.htm
Isthmus of
thyroid gland
Lobes of
thyroid gland
Now look at structures contained within
the carotid triangle of the anterior
cervical triangle.
Submandibular
gland.
Common carotid a.
This is a better view of that artery with
the SCM cut and reflected. Do NOT
perform this reflection unless you are told
to do so.
External carotid a.
Internal carotid a.
Common carotid a.
However, if you do reflect the
sternocleidomastoid m., you should be able
to easily view the spinal accessory nerve
(CN XI) on its underside.
While you are in this region, you will
observe some nerves which are components
of the ansa cervicalis which supply the
infrahyoid muscles.
Superior root of
ansa cervicalis
Inferior root of
ansa cervicalis
If you are told to do so, cut the
common facial vein where it joins
the internal jugular vein.
You should now be able to get a good
view of the hypoglossal nerve (CN XII).
It generally lies just medial to the
posterior belly of the digastric m.
Recall that this is the motor nerve to
the tongue.
Look even more superior to see
the occipital artery.
Occipital a.
Hypoglossal nerve (CN XII)
Other structures of interest in
this region are the internal
jugular vein and the vagus nerve.
Superior root of the
ansa cervicalis
Superior
thyroid a.
Internal jugular v.
Vagus nerve
Submental
triangle
Identify and clean the
suprahyoid muscles.
Identify and clean the
suprahyoid muscles.
Anterior bellies of
the digastric mm.
Mylohyoid m.
Stylohyoid m.
Hypoglossal n.
Posterior belly of
the left digastric m.