Triangles of the Neck
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of the neck | Main Anatomy
Index | Neck Index | Root
of the neck
Last updated 1 April 2006
Posterior Triangle of the Neck
Boundaries of the Posterior Cervical Triangle
- The clavicle forms the base of
the posterior triangle.
- The apex is formed where
the borders of the sternocleidomastoid and the trapezius
muscles meet on the superior nuchal
line of the occipital bone.
- The occipital artery
passes through the apex of the posterior triangle before
it ascends over the posterior aspect of the head.
Roof of the Posterior Cervical Triangle (p.
- The posterior triangle is covered by deep fascia, which
covers the space between the trapezius and the
- Superficial to the deep fascia are the superficial
fascia, platysma, superficial veins, cutaneous nerves,
Floor of the Posterior Cervical Triangle (p.
Click here for a
diagram of the floor of the posterior cervical triangle.
Contents of the Posterior Triangle
Veins of the Posterior Cervical Triangle (p. 790)
- The external jugular vein
begins near the angle of the mandible, just inferior to
the lobule of the auricle, by the union of the posterior division of the retromandibular
vein with the posterior
- It crosses the sternocleidomastoid in the superficial
fascia and then pierces the deep fascial roof the
triangle at the posterior border of this muscle, about 5 cm superior to the clavicle.
- The external jugular vein passes obliquely through the
inferior part of the posterior triangle and usually ends
by emptying into the subclavian
vein about 2 cm superior
to the clavicle.
Arteries of the Posterior Cervical Triangle (p. 791)
- The third part of the subclavian
artery begins about a fingerbreadth superior
to the clavicle, opposite the lateral border of the
scalenus anterior muscle.
- It is hidden in the inferomedial part of the triangle and
barely qualifies as one of its contents.
- The artery is in contact with the first
rib posterior to the scalenus anterior muscle
and can be compressed against this rib to control
bleeding in the upper limb.
- The transverse cervical artery
arises from the thyrocervical trunk,
a branch of the subclavian artery.
- It runs superficially and laterally across the posterior
triangle, 2 to 3 cm superior
to the clavicle.
- The occipital artery, a
branch of the external carotid artery, enters the apex of
the posterior triangle before ascending to the posterior
aspect of the head.
Nerves in the Posterior Cervical Triangle (p. 791)
Click here for a
diagram of the superficial nerves of the neck.
- The accessory nerve (CN
XI) divides the posterior triangle into nearly equal
superior and inferior parts.
- It enters the posterior triangle at or inferior to the
junction of the superior and middle thirds of the
- It runs between the trapezius and the sternocleidomastoid
muscles and supplies motor fibres to them both.
- It disappears deep to the anterior border of the
trapezius at the junction of its superior 2/3 and
- The superior part of the posterior cervical triangle
contains only the lesser occipital
- The inferior part contains numerous important nerves
(e.g., the ventral rami of the brachial plexus).
Plexus of Nerves (pp. 792-3)
- This is a network of nerves formed by the communications
between the ventral rami of the superior four cervical
- The plexus lies deep to the internal
jugular vein and the sternocleidomastoid
- Cutaneous branches emerge around the middle of the
posterior border of the SCM to supply the skin of the
neck and scalp, between the auricle and the external
lesser occipital nerve (C2, and sometimes C3)
ascends a short distance along the posterior border of
the SCM before dividing into several branches that supply
the skin of the neck and scalp posterior to the auricle.
great auricular nerve (C2 and C3) curves over
the posterior border of the SCM and ascends vertically
towards the parotid gland.
- It supplies branches to the skin of the neck and then
divides into anterior and posterior branches
- These supply the skin on the inferior part of the auricle
on both surfaces, and an area extending from the mandible
to the mastoid process.
- The transverse cervical nerve
from C2 and C3 curves around the posterior border of the
SCM near its middle, and then passes transversely across
- Its branches supply the skin over the anterior triangle
of the neck.
supraclavicular nerves (C3 and C4) arise as a
single trunk, which divides into medial, intermediate and
- They send small branches to the skin of the neck and then
pierce the deep fascia just superior to the clavicle to
supply the skin over the anterior
aspect of the chest and shoulder.
- The medial and lateral supraclavicular nerves also supply
the sternoclavicular and acromioclavicular joints,
phrenic nerve is the sole motor nerve supply
of the diaphragm.
- It arises from the ventral primary rami of C3 to C5 and
is an important muscular branch
of the cervical plexus.
- The phrenic nerve curves around the lateral border of the
anterior muscle. It then descends obliquely across
its anterior surface, deep to the transverse cervical and
- The phrenic nerve enters the thorax by crossing the
origin of the internal thoracic artery between the
subclavian artery and vein.
Click here for a diagram
of the ansa cervicalis.
- It is formed by branches from C1-3 and a branch of the
hypoglossal nerve (which contains fibres from C1).
- It descends anterior to or in the carotid sheath.
- It supplies the infrahyoid muscles.
Anterior Triangle of the Neck
Boundaries of the Anterior Cervical Triangle
- Medially: anterior median line of the neck.
- Anteriorly: inferior border of the mandible.
- Laterally: anterior border of SCM.
- Its apex is at the jugular notch.
- Its base is formed by the inferior
border of the mandible and a line drawn from
the angle of the mandible to the
- This triangular region is used for approaching many
important structures in the neck (e.g., larynx, trachea,
and thyroid gland).
- Using the digastric and omohyoid muscles, it is common to
divide the anterior triangle into smaller submandibular,
submental, carotid, and muscular triangles to descriptive
Floor of the Anterior Cervical Triangle (p.
- The floor of the anterior triangle of the neck is formed
mainly by the pharynx, larynx, and thyroid gland.
- Deep to these structures is the prevertebral fascia
covering the prevertebral muscles.
Contents of the Anterior Cervical Triangle (p.
- This triangle contains the suprahyoid and infrahyoid
muscles, arteries, veins, nerves, lymph nodes, and
viscera (e.g., thyroid gland).