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only to the integument in the neck. \w such an event, and usually in case of any deficiency,
the unsupplied area receives fibres from the great occipital. It sometimes jiasses backward
instead of upward and pierces the trapezius near the upper border before reaching the scalp.

2. The great auricular nerve (w. auricularis niatinus) (Fig. 1087) is the larg-
est of the su])erficial set and arises, usually with the su])erhcial cervical nerve, from
the second and third, from the third alone, or from the third and fourth cervical
nerves. Turning over the posterior margin of the sterno-mastoid it ascends toward
the ear between the platysma and the deep fascia. Below the ear it gi\-es off a few
(a) facial twigs and then terminates by dividing into {b) auricular and (r) mastoid
branches.

a. The facial twigs pass through the parotid gland and over the angle of the mandible,
supplying the integument over the parotid gland and masseter muscle and communicating with
the cervico-facial division of the seventh cranial nerve.

b. The auricular branches (r. anterior) supply mainly the cranial surface of the posterior
part of the jiinna. One filament passes through the cartilage by means of a cleft between the
concha and the antihelix and supplies the outer surface, while a few twigs are distributed to the
outer surface of the lobule. The auricular branches inosculate with the small occipital and pos-
terior auricular nerves.

c. The mastoid branch ( r. posterior") is distributed to the .skin overlying the mastoid process
and the upper part of the sterno-mastoid muscle. It inosculates as does the auricular branch.

Variation. — The mastoid branch may arise independently from tiie ple.xus and pass upward
to its destination between the small occipital and great auricular nerves.



TIIK CKRVICAL PLEXUS.



12S7



. The superficial cervical nerve ( n. cutancus colli) usually arises in com-
n.on with the ,^reat auricular iron, the second and third, the thu'd cnly, or f-m the
Sirdandfourthcervicalnerves(Fi<,Mo87). ^^^ ^^^ firTlTn^^^Z
mastoid it passes almost direcdy forward over the nuddle of that muscle and under

iMC. 1087.



Temix)ral branch official _



Occipital branch of
great auricular



Great occipital nerve.



Posterior auricular nerve
Small occipital nerve

Branch of communication with facial

Cutaneous branch of III. cervical

Great auricular nerve



Communication between
cervical nerves and

spinal accessory

Supraacromial branch
Supraclavicular branch




Supraorbital nerve

Supratrochlear
nerve

Malar branch of
firial nerve



ifraorbital
nerve



nfraorbital
branch of facial



Communication with
buccal branch of
mandilmlar

Supramandibular
branch of facial



Spinal accessory



Inframandibular branch
of facial



Superficial cervical nerve



Superficial descending branch
Suprasternal branch



the platvsma myoides and the external jugular ^•ein It perforates the deep cervical
fascia near the anterior border of the sterno-mastoid and divides into {a) an icpper
and (^) a /oTfer set of branches.

a. The upper branches ( rr. superiores) form an extensive inosculation witli ^'^^ ''^f "^i];-
ular branch of the facial nerve, after which they pierce the platysma and ^"Pfl^ '^ '';\^2Se
of the neck as far forward as the median line and as far up as the interior "^^Ff;" ^^.^^,%";^^7,^^^^

b The lower branches ( rr. inferiores ) after piercnig the platysma are distributed to the skm
of the lower part of the neck to the mid-line as tar down as the sternum.



1288



HUMAN ANATOMY



Variation. — The superficial cervical, instead of a single nerve, may arise as two or more
filaments from the cervical plexus.

The descending branches ( nn. supraclaviculares) (Fig. 1089) arise from the
third and fourth cervical nerves and pass downward in the anterior margin of the
occipital triangle along the posterior edge of the sterno-mastoid. On nearing the
clavicle they break up into three distinct sets : (4) the suprasternal, (5) the supra-
clavicular and (6) the supraacroviial.

Fig. 10.S8.



■m



Third occipital nerve

Great occipital nerve



Branch from III. cervical,
dorsal division "



Branches trora IV. cer-
vical, dorsal di\'isioii




Inosculation between facial nerve and
small occipital and great auricular

ntrves



Sterno-cleido-mastoid muscle

Great auricular nerve
Small occipital ners-e




_^ Superficial cervical nerve



.Superficial descending branch of cervical plexus;
the leader crosses the suprasternal br.inch
Spinal accessory nerve
Muscular branch to trapezius



Supraclavicular branches

Supraacroniial branches



Dissection showing superficial branches of cervical plexus and posterior cutaneous branches.

4. The suprasternal branches (rr. supraclaviculares antcriores) are the
smallest. They pass over the lower end of the sterno-mastoid and the inner end of
the clavicle and supply the skin of the chest as far down as the angulus Ludovici.
One or two filaments terminate in the sterno-clavicular articulation.

5. The supraclavicular branches (rr. supraclaviculares medii) pass across
the middle of the clavicle and supply the integument of the chest as far down as the
third or fourth rib, inosculating with twigs from the anterior cutaneous branches of
the upper thoracic nerves.

Variation. — A twig may perforate the clavicle.



thp: cervical plkxis.



1289



6. The supraacromial branches (rr. supraclavicularcs postcriorcs) cross the cla-
vicular insertion of the trapezius and are distributed to the skin over the anterior, external
and posterior aspects of the shoulder as far down as the lower portion of the deltoid.

II. The deep branches are divided into two sets, an external and an internal.
Both arising" beneath the sterno-mastoid, the former pass away from and the latter
toward the median line of the neck.

7. The external muscular branches are clistril)uted as follows: —

a. The sterno-mastoid receives a l)ranch from tlie second cervical which enters the deep
surface of the nuisclc and interlaces witli a branch of the spinal accessory nerve to form the
sterno-mastoid plexus.

, Fig. 1089. \



.1



">^




Small occipital
Coniplexus

Muscular brs. to complexus and

biventer from occip. major

Third occipital nerve

Fascial septum from ligamentum niichne

Great occipital nerve

Rectus capitis posticus major

Branch to obliquus inferior

Spine of II. cervical vertebra

Cutaneous br. from in. cervical

Part of complexus and biventer

Third occipital nerve

Branch to complexus from 11. cervical

Branch to complexus from III. cervical



II. cervical nerve, uorsal di
Levator anguli scapulas
Branch to trachelo-mastoid

III. cervical nerve, dorsal division
Communication between II. and III. dorsal division
External brs. of III. cervical, dorsal division
IV'. cervical nerve, dorsal division
Ext. branch of dorsal division \'. cervical ner\e




ot atlas

Ant. division I. cervi-
cal, cutaneous br. of
dorsal division passing
backward



VIII. cervical, dorsal division
Internal br. of post. div. of V. cervical nerve



Spinous process of \TI. cer



Transverse process I. thoracic vertebra



Transverse process II. tlioracic vertebra
Levator anguli scapul.'e



Dissection of right side of neck, showing deeper relations of cer^'ical nerves.

b. The trapezius receives fibres from the third and fourth cervical nerves which arise with
and accompany the descending branches of the superficial set through the occipital triangle.
They dip under the anterior margin of the trapezius, before and after which tliey form a more
or less complex inosculation with the spinal accessory, called the subtrapezial plexus, from
which filaments are distributed to the trapezius muscle (Fig. 1088).

c. The levator anguli scapulae receives two branches which take their origin from the tb.ird
and fourth nerves.

d. The scalenus medius and (c) scalenus posticus also receive fibres from the third and fourth.

8. The communicating branches form points of contact and union with
the spinal accessory nerve (a) under the sterno-mastoid and {b') in the occipital
triangle and under the trapezius. By means of these inosculations are formed the
sterno-mastoid and subtrapezial plexuses.



I290 HL'MAX ANATOMY.

9. The muscular branches arc distrihuted to (a) certain j)rfvcrtoI)ral muscles
and to (d) the j4ciii<)-h\()id and llu- inlrahyoitl muscles.

a. Tlie rectus capitis anticus major and minor and IIk- rectus capitis lateralis are siip]ilied
by a filanunt arising fmni tlie looj) bc-tucen the fnst and second cervical nerves. Tlie intcrtrans-
versales, the longus colli and a portion of tlie rectus capitis anticus major receive their su|)ply
from the second, third and fourth, and the ujjper part of the scalenus anticus receives a twig
from tile fourth cervical nerve.

d. The genio-hyoid and the four muscles of tlie infrahyoid group are innervated by the
cervical plexus in a rather roundabout manner. From the first and .second cervical nerves are
given off one or more branches which join the hypoglossal nerve shortly after its appearance in
the neck. Tliese fibres for a time form an integral portion (jf the hypoglossal and eventually
escajie from it as the nerve to the genio-hyoid, the nerve to the thyro-hyoid and the n. descen-
dens hypoglossi (F"ig. 10.S2). The last-mentioned nerve leaves the hypoglossal at the point
where the latter crosses tlie internal carotid artery and then descends in the anterior cervical
triangle. In front of, or .sometimes within, the carotid sheath it forms a loop of communication,
called tlie hypoglossal loop or ansa cervicalis (ansa iiypoglossi ) by inosculation with the
descending cervical nerve (n. descenders cervicalis) (Fig. iO(S2). This descending cervical nerve
is derived iroiu the second and tiiird cervical nerves and at finst consists of two twigs which later
unite in front of the internal jugular vein. From this point it passes downward and inward as a
single trunk to reach its point of entrance into the ansa hypoglossi. The ansa may be either a
simple loop or a plexus and is situated anterior to the carotid sheath at a variable point in the
neck. From it branches are given ofT to the sterno-hyoid, the sterno-thyroid and the posterior
belly of the omo-hyoid (Fig. 1076).

10. The phrenic nerve (n. phrcnicus), although an internal muscular branch
of the cervical plexus, is of such importance as to merit a separate description.
Whilst mainly the motor nerve to the diaphragm, it contains some sensory fibres ; in
this connection it may be pointed out that the phrenic is not the only motor nerve
to the diaphragm, the lower thoracic nerves aiding in its innervation. The phrenic
arises mainly from the fourth cervical nerve but receives additional fibres from the
third and fifth (Fig. 1090). It passes down the neck on the scalenus anticus, which
it crosses from without inward, and at the base of the neck accompanies that muscle
between the subclavian artery and vein. At the entrance to the thorax it passes
over the root of the internal mammary artery from without inward and backward,
occupying a position behind the sterno-clavicular articulation and the point of junc-
tion of the subclavian and internal jugular veins. It then follows a course almost
vertically downward, over the apex of the pleura and through the superior and
middle mediastina, to the upper surface of the diaphragm.

The right phrenic (Fig. 1090) is shorter than the left on account of its
more direct downward course and the greater ele\'ation of the diaphragm on
that side. It crosses the second part of the subclavian artery and accompanies
the right innominate vein and the superior vena cava on their lateral aspect.
It then passes in front of the root of the lung and finishes its course by de-
scending between the lateral aspect of the pericardium and the mediastinal pleura.
Nearing the diaphragm it breaks up at the antero-lateral aspect of the quadrate
foramen into its terminal branches, a few of which enter the abdomen through
this opening.

The left phrenic (Fig. 1090), having to wind around the left side of the
heart and reach the more inferior half of the diaphragm, is longer than its fellow,
about one-seventh longer (Luschka). Entering the thorax between the subclavian
artery and the left innominate vein it cro.s.ses the anterior face of the left vagus ner\e
and continues its downward course by passing over the left side of the aortic arch.
Reaching the middle mediastinum it courses in front of the root of the lung, behind
the lower left angle of the pericardium, and descends to the diaphragm between the
pericardium and the mediastinal pleura. It breaks up into its terminal branches
before arriving at the thoracic surface of the diaphragm, which it enters at a point
further from the median line and more anterior than does the right.

Branches of the phrenic nerve are : (a) the />/eura/,(d) the pericardiac and
(r) the terminal.



THE CKRXICAL PLKXl'S.



1 29 1



a. The pleural branches, two in number, are almost microscopic in size, and are given
off as the nerve crosses tin- ajKx of the pleura. One supplies the costal pleura and the other,
which sometimes accomjjanies the internal mammary artery, is distributed to the medias-
tinal pleura.

d. The pericardiac branch (r. pericardinciis ) is a tiny filament which is usually given off
opposite the lower mariL^in of tiie thirtl costal cartilage. It is sometimes absent on the left side.

r. The terminal branches arise uiukr cover of the pleura anti differ to some e.xtent on
the two sides.

The riffht phrenic divides antero-lateral to the opening for the inferioi' vena cava into (aa)
an anterior and (bb) a posterior branch.

aa. The anterior branch l)reaks up under the pleura into five or si.x fine twigs, \\ hich spread
out antero-laterally in the sternal portion and the anterior part of the right costal portion of the

Fig. 1090,



Scalenus incdius muscle

Vagus nerve-

V. cervical nerve

Scalenus anticus muscle

I'pper trunk of brachial plexus

VII. cer\-ical nerve

Superior intercostal a

Vni. cenical nerve '

I. thoracic nerve
Clavicle

Phrenic nerve

Internal mam-
mary artery



Innominate veins

Vena cava superior

l.ung, mesial surface



Pericardium




Sterno-cleido-mastoid
Vagus ner\-e
Internal jugular vein
Subclavian artery
Omo-hyoid muscle
Subclavian vein
Clavicle

Subclavius muscle



-'Lrib



Manubrium sterni

Vagus ner\-e
Phrenic nerve



Lungr. mesial surface.
^^^' ' sho^^ing hilum



— IV. rib




Diaphragm, up-
per surface



Dissection showing phrenic nerves; parts ot sternum and rihs have been removed ; lungs are pulled aside;

pericardium is undisturbed.

diaphragmatic musculature. Tiny filaments traverse the interval between the sternal and costal
portions and enter the abdomen, where they are distributed to the peritoneal covering of the
diaphragm and to the falciform ligament of the liver in the direction of the umbilicus.

bb. The posterior branch pierces tlie central tendon at the outer margin of the quadrate
opening and divides into a niuscu/ar branch and the right phrenico-abdoinina/ branch { r. phrenico-
abdominalis dexter ). The former supplies the lumbar portion of the musculature of the diaphragm.
The latter traverses the quadrate foramen and first gives off a recurrent branch which accompanies
the inferior vena cava back to the right auricle. After giving off this branch, under cover of the
peritoneum some of its fibres enter the diaphragmatic ganglioji and others unite with filaments
from the cceliac plexus to form at the inferior surface of the diaghragm the diaphragmatic
plexus, which is joined by twigs from the diaphragmatic ganglion. From this plexus fibres
are distributed to the coronary ligament and peritoneum of the liver and to the right supra-
renal body.

The left phrenic pursues a general antero-lateral course and pierces the diaphragm at the
junction between the musculature and the central tendon. Under cover of the peritoneum it
splits up into an anterior, a lateral and a posterior branch. The ante nor branch supplies the
muscle of the left sternal portion and the antero-lateral part of the left costal portion. The



1292 HUMAN ANATOMY.

lateral branch supplies the corresponding part of the left costal portion. '\\\it posterior branch
(r. phrenicoabdominalis sinister) is distributed to the left lumbar |)ortion of the muscle of the
diaphragm and usually either a filament j>asses to the left semilunar ganglion or several small
threads to the ccL-Iiac plexus, one of which can be traced to the left suprarenal body.

The phrenic nerve communicates in the lower part of the neck with the middle or inferior
cervical ganglion of the symi)athetic. At the inferior aspect of the diaphragm it ccjmmunicates,
on the right side, with the diaphragmatic ple.\us of the sympathetic and, on the left side, with
the semilunar ganglion or the cceliac plexus.

Variations. — Tlie })lirenic may receive additional roots from the nerve to the subclavius,
the nerve to the sternohyoid, the second or the sixth cervical nerve, the n. descendens cer\'i-
calis or the ansa hy|X)glossi. It m.ay arise exclusively from the nerve to the sulxlaviusor, aris-
ing normally, may give a branch to that muscle. It .sometimes |)asses along the lateral border
of or pierces the scalenus anticus muscle. Instead of descending behind the subclavian vein it
may pass anterior to it or even through a foramen in it.

The accessory phrenic nerve arises either from the fifth alone or from the fifth and sixth
cervical ner\es and, entering the thorax either anterior or posterior to the subclavian vein,
joins the phrenic at the base of the neck or in the thorax.

II. The communicating branches of the internal set effect unions with (a) the sympathetic,
(i) the vagus and kc) the hypoglossal.

a. The superior cervical ganglion of the sympathetic or the association cord connecting
the superior and middle ganglia sends gray rami communicates to the first, second, third and
fourth cer\ical ner\es.

b. The ganglion of the trunk of the vagus is sometimes connected by means of a tiny
nerve with the loop between the first and second cervical nerves

c. The hypoglossal nerve receives, just below the anterior condyloid foramen, a good
sized branch from the loop between the first and second cervical nerves. This- communication
furnishes sensor}- fibres to the hypoglossal ner\e which subsequently leaves the latter as its men-
ingeal branch ; other spinal fibres leave the twelfth as the n. descendens hypoglossi and as the
nerves to the genio-hyoid and thyro-hyoid muscles.

Practical Considerations. — Of the motor nerves of the cervical plexus the
phrejiic is most commonly the seat of trouble and this may result in or be associated
with spasm or paralysis of the diaphragm. The involvement of the diaphragm may
be part of a progressive muscular paralysis, as from lead poisoning, or from injuries
or diseases of the spine. The nerve may be compressed by tumors or abscesses of
the neck, or be injured in wounds of the neck. It passes downward under the sterno-
mastoid muscle and on the scalenus anticus, from about the le\el of the hyoid bone.
It is covered and somewhat fixed by the layer of deep fascia covering the scalenus
anticus muscle. The clonic variety of spasm, singultus or hiccough, is very common,
and is occasionally though rarely dangerous by preventing rest and sleep ; it may
complicate apoplexy, peritonitis or chronic gastric catarrh.

If only one phrenic is paralyzed the disturbance of function is slight and not
easily recognized. In a bilateral paralysis, as from alcoholic neuritis, respiration
depends almost entirely on the intercostal muscles, since the diaphragm is completely
paralyzed. Dyspnoea, therefore, occurs on slight exertion. The epigastrium is
depressed rather than prominent and the lower border of the liver is drawn upward.

The S2iperjicia/ branches of the cervical plexus emerge together through the deep
fascia near the middle of the posterior border of the sterno-mastoid muscle, and from
this point pass in various directions. The auricularis magnus passes upward and
forward over the sterno-mastoid to the ear and parotid gland, the occipitalis minor
along the posterior margin of the same muscle to the scalp, and the superficial
cervical branch obliquely forward and upward to the submaxillary region. The
descending branches are three in number and pass respectively in the direction of
the sternum, clavicle and acromion. They give rise to little or no disturbance
when wounded.

THE BRACHIAL PLEXL'S.

The brachial plexus T plexus brachialis) is a somewhat intricate interlacement of
the anterior primary divisions of usually the lower four cervical and first thoracic
nerves. To these are sometimes added a branch from the fourth cervical, a branch
from the second thoracic, or branches from both of these nerves. The fasciculi form-



THE BRACHIAL PLEXUS.



1293



\n^ this plexus cmcrg^e in the interval between the scalenus antlcus and medius and
from the side of tlie neck pass beneath the clavicle and into the axilla through its aj)ex.
The plexus is dixided, therefore, into two portions, a cervical ox siipraclaviculay \yaxX.
(pars siipraclavicularis) and an axillary ox infraclavicular \yaxX. (pars infraclavicuiarisj.
In the posterior cervical triangle the plexus lies first above and then to the outer side
of the subclavian artery and vein, is crossed by the posterior belly of the onio-liyoid
muscle and is frequently threaded by the transverse cervical or the posterior scapu-
lar artery. After entering the axilla its component parts, while lying mainly to the
outer side, forma close fasces around the axillary artery, whose sheath they occupy.
In the u[ii")er part of the axilla the plexus is overlain by the subclaxins and pectoralis
major muscles and before dividing into its terminal branches it lies enclosed between
the pectoralis minor and subscapularis muscles.

Constitution and Plan. — In the various weavings of the component elements
of the plexus five stages can be recognized : (a) anterior primary divisions of
the spinal nerves, (3) trunks, (r) divisions, (at) cords and (c) terminal branches
(Fig. 109 1 ).

I-'lG. I09I.




Diagram illustrating plan of brachial plexus.



Emerging from the interval between the anterior and middle scalene muscles,
the fifth and sixth cervical nerves unite to form the outer or upper trunk, the
seventh alone is continued into the middle trunk, whilst the eighth cervical and first
thoracic fuse to form the inner or lower trunk. These trunks continue undivided
until slightly beyond the lateral margin of the scalenus anticus, each one then sepa-
rating into an anterior and a posterior division. These are of about equal size,
with the exception of the posterior division of the inner trunk, which is much smaller
than the others because the first thoracic nerve sends few if any fibres to the posterior
division. The six divisions, three anterior and three posterior, unite differently to
form three cords. The outer cord (fasciculus lateralis) is the bundle formed by the
union of the anterior divisions of the outer and middle trunks. The posterior cord
(fasciculus posterior) is the result of the fusion of the posterior divisions of all of the
trunks and the inner cord (fasciculus medialis) is the continuation of only the
anterior division of the inner trunk. The trunks are named in correspondence with



1294



HIM AX ANATOMY



their position as regards one anotlier, while the cords are denominated accordint^ to
their relation to the axillarv artery, the outer lying lateral to, the inner mesial to, and
the ])osterior behind, the artery.

Variations. — C<>nsideral)lc variety exists as rejjards the length of the coniixjnent nerve-
hundlfs in their several portions, division and iniion taking place at ditlerent levels in different
individuals. The fifth cervical nerve may pass in fnjnt of ur through the scalenus anticus. The
si.\th, tiiough not so fre(|uently as the fifth, may traverse the scalenus anticus. The seventh
cervical nerve, as the middle trunk, may hreak up into three branches, one going to each of
the three cords. The fibres of the posterior cord may arise from only the seventh and eighth,
or the sixth, seventii and eighUi cervical ner\es. IMexuses have been seen in which only two
cords, a smaller and a larger, were present, the latter taking the place of either the inner and
outer or the inner and posterior cords.

Communications. — The five nerves comprising the source of the plexus are



Online LibraryMangasar Mugurditch MangasarianThe story of Joan of Arc the witch-saint → online text (page 45 of 161)