bony skeleton of the neck

8/14/2019 Bony Skeleton of the Neck

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BONY SKELETON OF THE NECK


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Like other regions of the body, the neck has a central bony skeletal core upon whichother structures attach or are related. The bones of the neck consist of the base ofthe skull and the 7 cervical vertebrae.

If we take a look at the base of the skull, the major parts that are related to theupper neck are the:

1. Foramen magnum

2. Occipital condyle (articulates with the superior process of the atlas.

3. External occipital protuberance

4. Mastoid process

Below the base of the skull, you will find the vertebralcolumn. The top vertebrae (7 cervical) provide support for

the neck structures. You will also note that these vertebraeallow passage of an important arterial supply to the brainand brain stem, the vertebral artery.


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The 7th cervical vertebra starts to pick up characteristics of the upper thoracic vertebrae and may even produce a cervical rib, which crelated to the brachial plexus.

It has the same characterists as other typical cervical vertebra except that there is no foramen for the vertebral artery and it may not After the vertebral artery arises from the subclavian artery, it enters the transverse foramen of the 6th cervical vertebra bypassing the

The spinous process of the 7 cervical vertebra is longer than those of the other cervical vertebrae and is not buried under the ligamenTherefore, it is easy to see and to palpate and is called the vertebra prominens. This can serve as a surface landmark demarcating thethoracic regions of the body.

Anterior Neck

As with all regions of the body, your study should start out with a look at the living region being studied.In the neck, the following diagram points out the major landmarks of the neck.

C

omm

oncarotidartery (cc)

Inter

nalcarotidartery (ic)

Exter

nalcarotidartery(ec)

Carot

idsinus(cs)

Superficialstructures thatyou should knowfrom the lateralview of the neck.

sternom

astoid

trapezius

occipital

lymphnodes(on)

retroauri

cularlymphnodes(ran)

superfici

alcervicallymphnodes(scn)

subment

al lymphnodes(smn)

buccal

lymphnodes(bn)

parotid

lymphnodes(pn)

submand


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ibular

lymphnodes(notlabeledbut unerangle of

mandible)

It is very important to visually project deep structures onto the surface of a person or patient whenmaking educated clinical diagnoses. The first thing you will usually do during a physical examination is topalpate any superficial structure that you can so that you can tell if abnormal changes have occurred.Swollen lymph nodes will tell you if there is an infection in an area that is drained by the nodes. Thesuperficial group of nodes in the neck drain the skin of the face and nose, scalp and external ear. Thesubmental nodes also drain the tip of the tongue. Deeper regions of the head and neck drain into a deepgroup of lymph nodes and are less palpable.

In the anterior neck, you can palpate the cartilages of the larynx and trachea. The thyroid gland is closelyassociated with the cricoid cartilage and the tracheal rings and should always be palpated in a generalphysical examination of the neck. Another very important structure that is palpable is the carotid artery.You should practice taking a carotid pulse since this is one site that is probably most often used to checkto see if a person is still living.The carotid artery pulse can be felt by pushing lateral to the upper border of the thyroid cartilage just

under the anterior edge of the sternomastoid muscle.

Anterior Triangle of the Neck In Detail

The neck is arbitrarily subdivided into two triangles by the sternocleidomastoid muscle:

Triangles of the Neck Anterior Triangle Posterior Triangle

submental

(smen)

submandibular

(sm)

muscular-

visceral (mus)

carotid (car)

occipital

supraclavicular

(omoclavicular)

Starting above the hyoid bone in the anterior triangle, we have two small triangles: submental andsubmandibular (or digastric). We will start this study by looking at the submandibular triangle first thenthe submental.

The Submandibular Triangle


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e the skin over the mandible and upper neck is removed, you can identifysubmandibular triangle and its boundaries.

ndaries

mastoid & mandible above

anterior belly of digastric anteriorly (abd)

posterior belly of digastric (pbd) and stylohyoid posteriorly (sh)

superficial (roof) structures of the submandibular region are:

platysma

facial vein (fv)

cervical branch of facial nerve (cbf)


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moval of the superficial structures displays the submandibular salivary glandf.

remaining contents of the submandibular triangle are structures passingugh:

facial artery (fa)

lingual nerve and submandibular ganglion (ln)

submandibular duct (smd)

lingual artery (la)

hypoglossal nerve (XII)

ce that the lingual nerve and submandibular duct pass through a gapween the hypoglossal (hg) and mylohyoid (mh) muscles and the lingualry passes deep to the hyoglossus muscle.

The Submental Triangle


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The submental triangle is locatedbetween the two anterior digastricmuscles (abd). Structures found here are

the submental lymph node(s) (ln) thatdrain the floor of the mouth. The

mylohyoid muscle (mh) arise from thebody of the hyoid bone and insert intothe mylohyoid line of the inside of themandible. This muscle aids in swallowingand in depressing the mandible.

The Carotid Triangle

The boundaries of the carotidtriangle are:

posterior belly of

digastric muscle (pbd)

superior belly of the

omohyoid muscle (so)

anterior border ofsternomastoid muscle(st)

Boundaries of Carotid Triangle

Starting from the most superficial aspects of the carotid triangle, we will point out the items that arerelated to it.

Roof of carotid triangle Vein of the carotid triangle


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The first layer, under the skin and superficial fasciaincludes the platysma, which forms the roof of thecarotid triangle. Note the location of the carotidtriangle in purple.

With the roof removed, you can see the boundariesof 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)

The nerves that enter the carotid triangle and that liesuperficial to the internal jugular vein, internal andexternal carotid arteries are:

hypoglossal (XII)

C1 root of ansa cervicalis (C1)

C1 fibers running with hypoglossal nerve

(nerve to thyrohyoid muscle (nth)

C2-C3 root of ansa cervicalis

ansa cervicalis (ac)

Nerves within the carotid triangle


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Reflection of sternomastoid and removal ofcommon facial vein

cca-common carotid arteryeca-external carotid artery

sta -supterior thyroid artery

oa -occipital artery

la -lingual artery

fa -facial artery

ica -internal carotid artery

Finally, we reach the deepest aspect of the carotidtriangle, frequently called the floor. The muscles, atthis level, are the middle and lower pharyngealconstrictors (mpc and ipc). The structures seenpassing through this level are:

superior laryngeal nerve, a branch of the

Floor of the carotid triangle


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vagus its 2 terminal branches

internal laryngeal (ilb--sensory to upper part

of the larynx)

external laryngeal (elb--motor to the cricoid

muscle)

Muscular or Visceral Triangle

The muscular triangle hasthe following boundaries:

mid line of neck

(1)

superior belly of

omohyoid (2)

sternomastoid

(3)

The muscles forming andwithin the triangle areseen in image labeledMuscles (these musclesare often called the strapmuscles, for obviousreasons:

superficial layer

sternohy

oid (sh)

superior

belly ofomohyoid (oh)

deep layer

thyroid

(th)

sternoth

yroid

(st)

Boundaries Muscles


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When the strap musclesare reflected, you are ableto see the thyroid gland

(tg) with its arteries(superior thyroid arteryfrom the external carotid(sta) and the inferior

thyroid artery from thethyrohyoid trunk from the

subclavian (ita).

If the thyroid gland isreflected laterally, thestructures making up thelarynx and trachea areseen:

thyrohyoid

membrane (thm)

thyroid cartilage

(Adam's

apple)(tc)

cricothyroid

membrane andligament (ctm)

cricoid cartilage

(cc)

tracheal rings (tr)

Thyroid gland and it arterialsupply

Cartilages and membranes

The thyroid gland is

hidden under thesternohyoid andsternothyroid muscles andconsists of two lobes andan isthmus. An occasional

pyramidal lobe extendsupward near the mid line.The thyroid is supplied bysuperior (sta) and inferior(ita) thyroid arteriesderived from the externalcarotid and thyrocervical

trunk respectively. Theinferior thyroid artery isclosely associated with therecurrent laryngeal nerve(rln).

Anterior View of Thyroid Gland Deep Surface of Thyroid Gland

Four small reddish-brown pea-sizedglands may be seen on the deepsurface of the thyroid gland. These arethe superior and inferior parathyroidglands (ptg). Also note the close

relationship of the recurrent laryngealnerves to the thyroid gland andinferior thyroid artery (rln, ita).


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Clinical ConsiderationsThe cricothyroid ligament and membrane are frequently pierced in emergency situations to open theairway. You should be able to palpate this space on yourself or a friend, just to appreciate where it is. Ithas been known that an empty ball-point pen or a hollow stem has been used in the field to save lives,where an air passage has been closed above this region.

Structures Found AT the Root of the Neck

You will now disarticulate the sternoclavicular joint and identify the structures located at the root of the

neck. The root of the neck is bounded by the manubrium of the sternum anteriorly, the first rib laterallyand the first thoracic vertebra posteriorly. All structures passing from the head through the neck to lowerregions pass through this area as well as structures arising in the thoracic cavity and passing out throughthis region. The following description of the root of the neck starts with the most anteriorly placedstructures and proceeds to the most posteriorly placed ones.


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t anterior structures:

1. brachiocephalic vein

2. vertebral vein

3. internal jugular vein

4. subclavian vein

5. thoracic duct

6. thymus gland

next layer can be considered the artery-nerve layer:

1. lung

2. vagus nerve

3. common carotid artery

4. subclavian artery

5. ansa subclavius

6. thyrocervical trunk

7. vertebral artery

8. internal thoracic artery

9. trachea

10. esophagus


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upper lobe of the lung (1) extends into the neck region. This iscally important for anyone entering this region surgically since the

g can be punctured if the surgeon isn't careful.

posterior part of the root of the neck is made up of the anterior

ace of the body of the 1st thoracic vertebra with its anteriorgitudinal ligament (in gray). When observing this area, you can seenerves:

1. ventral ramus of C8

2. ventral ramus of T1

3. lower trunk of brachial plexus

4. stellate ganglion (inferior cervical + 1st thoracic ganglia)

List of Items Studied in this Section

Bones

mastoid process of temporal bone

body and angle of mandible

hyoid bone

body

greater horn

Arteries

common carotid

internal carotid

external carotid

superior thyroid

lingual


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lesser horn

manubrium of sternum

1st thoracic vertebra

1st rib

Cartilages

thyroid

superior horn

inferior horn

cricoid

tracheal rings

Muscles

sternomastoid

anterior belly of digastric

posterior belly of digastric

stylohyoid

mylohyoid

sternohyoid

omohyoid (superior belly)

sternothyroid

thyrohyoid

Nerves

hypoglossal

superior laryngeal

internal laryngeal branch

external laryngeal branch

vagus

recurrent laryngeal

sympathetic chain

stellate ganglion

facial

occipital

ascending pharyngeal

subclavian

thyrocervical trunk

inferior thyroid

suprascapular

transverse cervical

vertebral

internal thoracic (mammary)

Veins

facial

common facial

internal jugular

vertebral

Lymphatics

thoracic duct on left

right lymphatic duct on right

Viscera

submandibular gland

thyroid gland

parathyroid gland (maybe)

thymus

larynx

trachea

esophagus


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inferior cervical ganglion

1st thoracic ganglion

bony skeleton of the neck

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