unit 17 - anterior triangle of the neck
TRANSCRIPT
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The Anterior and Posterior
Triangles of the Neck
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Anterior Triangle of the Neck
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BONY SKELETON OF THE NECK
Like other regions of thebody, the neck has a centralbony skeletal core uponwhich other structures attachor are related. The bones ofthe neck consist of the base
of the skull and the 7 cervicalvertebrae.
If we take a look at the baseof the skull, the major partsthat are related to the upper
neck are the: Foramen magnum Occipital condyle (articulates
with the superior process of theatlas.
External occipital protuberance
Mastoid process
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Below the base of the
skull, you will find the
vertebral column. The top
vertebrae (7 cervical)provide support for the
neck structures. You will
also note that these
vertebrae allow passage
of an important arterialsupply to the brain and
brain stem, the vertebral
artery.
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The first cervical vertebra is theatlas and is considered an atypicalcervical vertebra because it has nobody or spinous process. Itarticulates with the occipital
condyles of the skull above it andwith the superior articularprocesses of the axis below it. Italso articulates with the dens of theaxis below. If viewed from above,you can identify the following partsof the atlas:
Anterior arch Anterior tubercle
Superior articular process(articulate with the occipital condyleof the skull)
Foramen transversarium
Transverse process
Posterior arch
Posterior tubercle
Vertebral canal (continuous with theforamen magnum at the base of theskull). The brain stem continuesinferiorly as the spinal cord at the
margin of the foramen magnum.
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The axis is the secondcervical vertebra. Thisvertebral is also called an
atypical vertebra because ithas an upward projectioncalled the dens thatarticulates with the inneraspect of the anterior arch of
the atlas just posterior to theanterior tubercle. Some ofthe identifiable parts are the: dens
body
superior articular process transverse process with its
vertebral foramen
pedicle
lamina
bifid spine
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The 3rd, 4th, 5th, and 6thcervical vertebrae are known asthe typical cervical vertebraebecause they all have the samecharacteristics and except forthe foramen for the vertebralartery similar to other typicalvertebrae of the spinal cord.These characteristics are:
body
pedicle
foramen for vertebral artery
superior articular process
lamina
spinous process (bifid in case of
cervical vertebrae) vertebral canal
transverse process (consists ofa groove that carries a cervicalspinal nerve and, of course theforamen for the vertebral artery)
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The 7th cervical vertebra starts to pick up
characteristics of the upper thoracic vertebrae. Differences from other cervical vertebrae no foramen for the vertebral artery
After the vertebral artery arises from the subclavian artery, itenters the transverse foramen of the 6th cervical vertebrabypassing the 7th
may not have a bifid spinous process
the spinous process of the 7 cervical vertebra islonger than the other cervical vertebrae
it is not buried under the ligamentum nuchae of theneck so it is easy to see and to palpate and is calledthe vertebra prominens
can serve as a surface landmark demarcating the neck(cervical) from the thoracic regions of the body.
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AnteriorNeck
Common carotid artery (cc)
Internal carotid artery (ic)
External carotid artery (ec)
Carotid sinus
MajorLandmarks
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Superficial structures
from the lateral view ofthe neck. sternomastoid
trapezius
occipital lymph nodes (on)
retroauricular lymph nodes(ran)
superficial cervical lymphnodes (scn)
submental lymph nodes(smn)
buccal lymph nodes (bn) parotid lymph nodes (pn)
submandibular lymphnodes (not labeled but unerangle of mandible)
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Abnormalities of the superficial neck Swollen lymph nodes sign of an infection in an area
that is drained by the nodes The superficial group of nodes in the neck drain the skin of
the face and nose, scalp and external ear.
The submental nodes also drain the tip of the tongue.
Deeper regions of the head and neck drain into a deep groupof lymph nodes and are less palpable.
Other important landmarks the cartilages of the larynx and trachea
the thyroid gland is closely associated with the cricoidcartilage
the tracheal rings the carotid artery
carotid artery pulse can be felt by pushing lateral to the upperborder of the thyroid cartilage just under the anterior edge ofthe sternomastoid muscle.
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AnteriorTriangleofthe Neck In
Detail
Anterior Triangle
submental (smen)
submandibular (sm)
muscular-visceral
(mus)
carotid (car)
Posterior Triangle
occipital
supraclavicular (omoc
lavicular)
The neck is arbitrarily subdivided into two triangles by the sternocleidomastoid muscle:
Starting above the hyoid bone in the
anterior triangle, we have two small
triangles: submental and submandibular
(or digastric). We will start this study by
looking at the submandibular triangle firstthen the submental.
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The SubmandibularTriangle
Boundaries mastoid & mandible
above anterior belly of
digastric anteriorly(abd)
posterior belly of
digastric (pbd) stylohyoid posteriorly
(sh)
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The superficial (roof)
structures of the
submandibular region
are:
platysma
facial vein (fv)
cervical branch of
facial nerve (cbf)
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The Submental Triangle
located between the two
anterior digastric muscles
(abd).
Structures submental lymph node(s)
(ln) - drain the floor of the
mouth.
mylohyoid muscle (mh)
arise from the body of thehyoid bone and insert into
the mylohyoid line of the
inside of the mandible.
aids in swallowing and in
depressing the mandible.
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The Carotid Triangle
The boundaries of the
carotid triangle are:
posterior belly of
digastric muscle (pbd) superior belly of the
omohyoid muscle (so)
anterior border of
sternomastoid muscle(st)
Starting from the most superficial aspects of the carotid triangle, we will
point out the items that are related to it.
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Roof of the Carotid Triangle
The first layer, under
the skin and
superficial fascia
includes theplatysma, which
forms the roof of the
carotid triangle. Note
the location of thecarotid triangle in
purple.
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Veins of the Carotid Triangle
With the roof removed, here
are the boundaries of the
carotid triangle and the
superficial veins related to it:
common facial vein (cf) (within
carotid triangle)
Other structures near by:
retromandibular vein (rm)
posterior auricular vein (pav) facial vein (fv)
external jugular vein (ej)
anterior jugular vein (aj)
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Nerves within the Carotid Triangle
The nerves that enter thecarotid triangle and thatlie superficial to theinternal jugular vein,internal and externalcarotid arteries are: hypoglossal (XII)
C1 root of ansa cervicalis(C1)
C1 fibers running withhypoglossal nerve (nerveto thyrohyoid muscle (nth)
C2-C3 root of ansacervicalis
ansa cervicalis (ac)
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Nerves within the Carotid Triangle
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Floor of the carotid triangle
The floor is the the deepestaspect of the carotid triangle.
The muscles, at this level, arethe middle and lowerpharyngeal constrictors (mpc
and ipc).
The structures seen passingthrough this level are:
superior laryngeal nerve, abranch of the vagus its 2terminal branches
internal laryngeal (ilb--sensoryto upper part of the larynx)
external laryngeal (elb--motorto the cricoid muscle)
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MuscularorVisceral Triangle The muscular triangle has the
following boundaries: mid line of neck (1)
superior belly of omohyoid (2)
sternomastoid (3)
The muscles forming and
within the triangle are seen inimage labeled (these musclesare often called the strapmuscles, for obvious reasons: superficial layer
sternohyoid (sh) superior belly of omohyoid (oh)
deep layer
thyroid (th)
sternothyroid (st)
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Thyroidglandand
itsarterialsupply
When the strapmuscles are reflected,you can see the
thyroid gland (tg) withits arteries (superiorthyroid artery from theexternal carotid (sta)and the inferior
thyroid artery from thethyrohyoid trunk fromthe subclavian (ita).
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If the thyroid gland is
reflected laterally, the
structures making up thelarynx and trachea are
seen:
thyrohyoid membrane
(thm)
thyroid cartilage (Adam's
apple)(tc)
cricothyroid membrane
and ligament (ctm) cricoid cartilage (cc)
tracheal rings (tr)
Cartilagesandmembranes
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AnteriorViewofThyroid Gland
The thyroid gland ishidden under thesternohyoid andsternothyroid muscles
and consists of two lobesand an isthmus.
An occasional pyramidallobe extends upward nearthe mid line.
The inferior thyroid arteryis closely associated withthe recurrent laryngealnerve (rln).
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Deep SurfaceofThyroid Gland
Four small reddish-brownpea-sized glands may beseen on the deep surfaceof the thyroid gland.
These are the superiorand inferior parathyroidglands (ptg).
Also note the closerelationship of the
recurrent laryngealnerves to the thyroidgland and inferior thyroidartery (rln, ita).
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Most anterior
structures:
brachiocephalic vein
vertebral vein
internal jugular vein
subclavian vein
thoracic duct thymus gland
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Thenextlayercanbe
consideredtheartery-
nervelayer:
lung
vagusnerve
commoncarotidartery
subclavianartery
ansasubclavius
thyrocervicaltrunk
vertebralartery
internalthoracicartery
trachea
esophagus
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The upper lobe of the
lung (1) extends into
the neck region. This
is clinically importantfor anyone entering
this region surgically
since the lung can be
punctured if thesurgeon isn't careful.
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The posterior part of theroot of the neck is madeup of the anterior surface
of the body of the 1stthoracic vertebra with itsanterior longitudinalligament (in gray). Whenobserving this area, you
can see the nerves:
ventral ramus of C8
ventral ramus of T1
lower trunk of brachialplexus
stellate ganglion (inferiorcervical + 1st thoracicganglia)
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Table of Muscles
Muscle Origin Insertion Action Nerve Supply
Sternohyoid sternum hyoid ansa
OmohyoidSuprascapularnotch
hyoid ansa
SternothyroidBelowsternohyoid onmanubrium
Thyroidcartilageoblique line
ansa
Thyrohyoid Thyroidcartilageoblique line
hyoid C1-C2 (ansa)
Anterior BellyDigastric
-----intermediatetendon------
Inner surface ofmandile
Trigeminalnerve
Posterior BellyDigastric
Medial aspectof the mastoidprocess
-intermediatetendon-
Facial nerve
MylohyoidMylohyoid lineof mandible
Hyoid boneTrigeminalnerve
Hyoglossus Hyoid boneLateral side oftongue
hypoglossal
Stylohyoid Styloid process hyoid Facial nerve