The document describes the triangles of the neck, including boundaries and contents. It discusses the anterior triangle, bounded by the middle line of the neck, anterior margin of sternocleidomastoid muscle, and lower border of mandible. This space contains muscles like the sternohyoid and structures like the common carotid artery and internal jugular vein. The posterior triangle is bounded by the sternocleidomastoid, anterior margin of trapezius, and middle third of clavicle. It contains the brachial plexus and transverse cervical vessels. The triangles are further divided and each contains specific muscles, glands, vessels and nerves.

1. Triangles ofTriangles of
the Neckthe Neck
By: Aljeirou D. Alcachupas

2. Muscles of the NeckMuscles of the Neck

5. Anterior TriangleAnterior Triangle
BoundariesBoundaries::
front,front, by the middle line of the neckby the middle line of the neck
behind,behind, by the anterior margin of the Sternocleidomastoid;by the anterior margin of the Sternocleidomastoid;
base,base, directed upward, formed by the lower border of the body of thedirected upward, formed by the lower border of the body of the
mandiblemandible
apexapex is below, at the sternum.is below, at the sternum.

6.  This space is subdividedThis space is subdivided
into four smaller trianglesinto four smaller triangles
by the Digastricus above,by the Digastricus above,
and the superior belly of theand the superior belly of the
Omohyoideus below. TheseOmohyoideus below. These
smaller triangles are namedsmaller triangles are named
thethe carotid,carotid, thethe
submandibular,submandibular, thethe
submental,submental, and theand the
muscular.muscular.

7.  Muscular TriangleMuscular Triangle
Boundaries:Boundaries:
 Front,Front, by the median line of theby the median line of the
neck from the hyoid bone to theneck from the hyoid bone to the
sternum;sternum;
 Behind,Behind, by the anterior margin ofby the anterior margin of
the Sternocleidomastoid;the Sternocleidomastoid;
 AboveAbove, by the superior belly of the, by the superior belly of the
Omohyoid. It is covered by theOmohyoid. It is covered by the
integument, superficial fascia,integument, superficial fascia,
Platysma, and deep fasciaPlatysma, and deep fascia

8.  The muscles forming and withinThe muscles forming and within
the triangle are seen in imagethe triangle are seen in image
labeled:labeled:
 superficial layersuperficial layer
 sternohyoid (sh)sternohyoid (sh)
 superior belly of omohyoidsuperior belly of omohyoid
(oh)(oh)
 deep layerdeep layer
 thyroid (th)thyroid (th)
 sternothyroid (st)sternothyroid (st)

9.  Contents: common carotid artery, internalContents: common carotid artery, internal
jugular vein and vagus nerve, inferior thyroidjugular vein and vagus nerve, inferior thyroid
artery, the recurrent nerve, and the sympatheticartery, the recurrent nerve, and the sympathetic
trunk , esophagus, the trachea, the thyroid gland,trunk , esophagus, the trachea, the thyroid gland,
and the lower part of the larynxand the lower part of the larynx

10. Thyroid gland andThyroid gland and
its arterial supplyits arterial supply
 When the strap musclesWhen the strap muscles
are reflected, you can seeare reflected, you can see
the thyroid gland (tg)the thyroid gland (tg)
with its arteries (superiorwith its arteries (superior
thyroid artery from thethyroid artery from the
external carotid (sta) andexternal carotid (sta) and
the inferior thyroid arterythe inferior thyroid artery
from the thyrohyoidfrom the thyrohyoid
trunk from thetrunk from the
subclavian (ita).subclavian (ita).

11.  If the thyroid gland isIf the thyroid gland is
reflected laterally, thereflected laterally, the
structures making up thestructures making up the
larynx and trachea are seen:larynx and trachea are seen:
 thyrohyoid membrane (thm)thyrohyoid membrane (thm)
 thyroid cartilage (Adam'sthyroid cartilage (Adam's
apple)(tc)apple)(tc)
 cricothyroid membrane andcricothyroid membrane and
ligament (ctm)ligament (ctm)
 cricoid cartilage (cc)cricoid cartilage (cc)
 tracheal rings (tr)tracheal rings (tr)
Cartilages and membranes

12. Anterior View of Thyroid GlandAnterior View of Thyroid Gland
 The thyroid gland is hiddenThe thyroid gland is hidden
under the sternohyoid andunder the sternohyoid and
sternothyroid muscles andsternothyroid muscles and
consists of two lobes and anconsists of two lobes and an
isthmus.isthmus.
 An occasional pyramidal lobeAn occasional pyramidal lobe
extends upward near the midextends upward near the mid
line.line.
 The inferior thyroid artery isThe inferior thyroid artery is
closely associated with theclosely associated with the
recurrent laryngeal nerverecurrent laryngeal nerve
(rln).(rln).

13. Boundaries:Boundaries:
 Above,Above, by the posteriorby the posterior
belly of digastricbelly of digastric
muscle and stylohyoidmuscle and stylohyoid
 Below,Below, by the superiorby the superior
belly of the omohyoidbelly of the omohyoid
muscle (so)muscle (so)
 BehindBehind, anterior border, anterior border
of sternomastoidof sternomastoid
musclemuscle
Carotid Triangle

14.  Roof of the carotid:Roof of the carotid:
The first layer, under theThe first layer, under the
skin and superficial fasciaskin and superficial fascia
includes the platysma,includes the platysma,
which forms the roof ofwhich forms the roof of
the carotid triangle. Notethe carotid triangle. Note
the location of thethe location of the
carotid triangle in purple.carotid triangle in purple.

15.  Floor of the carotid:Floor of the carotid:
The floor is the the deepestThe floor is the the deepest
aspect of the carotid triangle.aspect of the carotid triangle.
 The muscles, at this level, areThe muscles, at this level, are
the middle and lowerthe middle and lower
pharyngeal constrictors (mpcpharyngeal constrictors (mpc
and ipc).and ipc).
 The structures seen passingThe structures seen passing
through this level are:through this level are:
 superior laryngeal nerve, asuperior laryngeal nerve, a
branch of the vagus its 2branch of the vagus its 2
terminal branchesterminal branches
 internal laryngeal (ilb--sensoryinternal laryngeal (ilb--sensory
to upper part of the larynx)to upper part of the larynx)
 external laryngeal (elb--motorexternal laryngeal (elb--motor
to the cricoid muscle)to the cricoid muscle)

16.  Contents: upper part of the common carotidContents: upper part of the common carotid
artery, internal jugular vein, hypoglossal nerve,artery, internal jugular vein, hypoglossal nerve,
vagus nerve, accessory nerve, internal branch ofvagus nerve, accessory nerve, internal branch of
the superior laryngeal nerve, external branch ofthe superior laryngeal nerve, external branch of
the superior laryngeal nervethe superior laryngeal nerve

17.  Veins within the CarotidVeins within the Carotid
With the roof removed, here are theWith the roof removed, here are the
boundaries of the carotid triangleboundaries of the carotid triangle
and the superficial veins related toand the superficial veins related to
it:it:
 common facial vein (cf) (common facial vein (cf) (within carotidwithin carotid
triangle)triangle)
 Other structures near by:Other structures near by:
 retromandibular vein (retromandibular vein (rmrm))
 posterior auricular vein (posterior auricular vein (pavpav))
 facial vein (facial vein (fvfv))
 external jugular vein (external jugular vein (ejej))
 anterior jugular vein (anterior jugular vein (ajaj))

18. Nerves within the Carotid TriangleNerves within the Carotid Triangle

19.  The nerves that enter theThe nerves that enter the
carotid triangle and thatcarotid triangle and that
lie superficial to thelie superficial to the
internal jugular vein,internal jugular vein,
internal and externalinternal and external
carotid arteries are:carotid arteries are:
 hypoglossal (XII)hypoglossal (XII)
 C1 root of ansa cervicalisC1 root of ansa cervicalis
(C1)(C1)
 C1 fibers running withC1 fibers running with
hypoglossal nerve (nervehypoglossal nerve (nerve
to thyrohyoid muscleto thyrohyoid muscle
(nth)(nth)
 C2-C3 root of ansaC2-C3 root of ansa
cervicaliscervicalis
 ansa cervicalis (ac)ansa cervicalis (ac)

20. Reflection of sternomastoid andReflection of sternomastoid and
removal of common facial veinremoval of common facial vein
 ccacca-common carotid artery-common carotid artery
ecaeca-external carotid artery-external carotid artery
 stasta-supterior thyroid artery-supterior thyroid artery
 oaoa-occipital artery-occipital artery
 lala-lingual artery-lingual artery
 fafa-facial artery-facial artery
 icaica-internal carotid artery-internal carotid artery

21. Arteries in the Carotid TriangleArteries in the Carotid Triangle

22.  corresponds to the region of thecorresponds to the region of the
neck immediately beneath theneck immediately beneath the
body of the mandible.body of the mandible.
Boundaries:Boundaries:
 Above,Above, by the lower border of theby the lower border of the
body of the mandible and thebody of the mandible and the
mastoid processmastoid process
 Below,Below, by the posterior belly ofby the posterior belly of
the Digastric and the Stylohyoid;the Digastric and the Stylohyoid;
 Front,Front, by the anterior belly of theby the anterior belly of the
Digastric.Digastric.
 Floor,Floor, coverd by mylohiodeuscoverd by mylohiodeus
Submandibular
Triangle

23.  The superficial (roof)The superficial (roof)
structures of thestructures of the
submandibular regionsubmandibular region
are:are:
 platysmaplatysma
 facial vein (fv)facial vein (fv)
 cervical branch of facialcervical branch of facial
nerve (cbf)nerve (cbf)

24.  Contents:Contents:
Anterior part:Anterior part:
submaxillary gland,submaxillary gland,
anterior facial vein,anterior facial vein,
external maxillaryexternal maxillary
artery, submentalartery, submental
artery, mylohyoidartery, mylohyoid
artery and nerve,artery and nerve,
external carotidexternal carotid
artery, internalartery, internal
carotid artery, facialcarotid artery, facial
nervenerve

25.  Removal of the superficialRemoval of the superficial
structures displays thestructures displays the
submandibular salivary glandsubmandibular salivary gland
itself.itself.

26.  contents of thecontents of the
submandibular triangle aresubmandibular triangle are
structures passing through:structures passing through:
 facial artery (fa)facial artery (fa)
 lingual nerve andlingual nerve and
submandibular ganglionsubmandibular ganglion
(ln)(ln)
 submandibular duct (smd)submandibular duct (smd)
 lingual artery (la)lingual artery (la)
 hypoglossal nerve (XII)hypoglossal nerve (XII)
 the lingual nerve andthe lingual nerve and
submandibular duct passsubmandibular duct pass
through a gap between thethrough a gap between the
hypoglossal (hg) andhypoglossal (hg) and
mylohyoid (mh) musclesmylohyoid (mh) muscles
 the lingual artery passes deepthe lingual artery passes deep
to the hyoglossus muscle.to the hyoglossus muscle.

27. Submental TriangleSubmental Triangle
BoundariesBoundaries
BBehind,ehind, by the anterior bellyby the anterior belly
of the Digastricusof the Digastricus
Front,Front, by the middle line ofby the middle line of
the neck between the mandiblethe neck between the mandible
and the hyoid boneand the hyoid bone
Below,Below, by the body of theby the body of the
hyoid bone;hyoid bone;
FloorFloor is formed by theis formed by the
Mylohyoideus which aids inMylohyoideus which aids in
swallowing and in depressingswallowing and in depressing
the mandible.the mandible.
 StructuresStructures
 submental lymph node(s) (ln) -submental lymph node(s) (ln) -
drain the floor of the mouth.drain the floor of the mouth.
 some small veins; the lattersome small veins; the latter
unite to form the anteriorunite to form the anterior
jugular vein.jugular vein.

28. Posterior TrianglePosterior Triangle
BoundariesBoundaries::
Front,Front, by the Sternocleidomastoid;by the Sternocleidomastoid;
Behind,Behind, by the anterior margin of the Trapezius;by the anterior margin of the Trapezius;
BaseBase, by the middle third of the clavicle, by the middle third of the clavicle
Apex,Apex, by the occipital bone. The space is crossed, above the clavicle, byby the occipital bone. The space is crossed, above the clavicle, by
the inferior belly of the Omohyoid, which divides it into, anthe inferior belly of the Omohyoid, which divides it into, an upperupper oror
occipital,occipital, and aand a lowerlower oror supraclavicular.supraclavicular.

29. Occipital TriangleOccipital Triangle
Boundaries:Boundaries:
Front,Front, by theby the
SternocleidomastoidSternocleidomastoid
Behind,Behind, by the Trapeziusby the Trapezius
Below,Below, by the Omohyoid.by the Omohyoid.
FloorFloor is formed from aboveis formed from above
downward by the Spleniusdownward by the Splenius
capitis, Levator scapulæ, andcapitis, Levator scapulæ, and
the Scaleni medius andthe Scaleni medius and
posterior.posterior.

30.  It is covered byIt is covered by
the skin, thethe skin, the
superficial andsuperficial and
deep fasciæ, anddeep fasciæ, and
by the Platysmaby the Platysma
below.below.

31.  Contents: accessoryContents: accessory
nerve, supraclavicularnerve, supraclavicular
nerves and thenerves and the
transverse cervicaltransverse cervical
vessels, lymph nodes,vessels, lymph nodes,
brachial plexusbrachial plexus

32. Supraclavicular TriangleSupraclavicular Triangle
Boundaries:Boundaries:
Above,Above, by the inferiorby the inferior
belly of the Omohyoid;belly of the Omohyoid;
Below,Below, by the clavicle;by the clavicle;
BaseBase is formed by theis formed by the
posterior border of theposterior border of the
Sternocleidomastoid.Sternocleidomastoid.
floorfloor is formed by theis formed by the
first rib with the firstfirst rib with the first
digitation of the Serratusdigitation of the Serratus
anterior.anterior.

33.  Contents:Contents:
 third portion of thethird portion of the
subclavian artery,subclavian artery,
 subclavian vein,subclavian vein,
 cervical artery,cervical artery,
 external jugular veinexternal jugular vein
 lymph nodes.lymph nodes.