6.2 The Neck

Platysma

Broad sheet fo fibres, but may be atrophic / not seen in elderly.
Superficial to deep cervical fascia of neck and to jugular veins.
From midline down beyond clavicals and up to mandibles; little posterior to EJV
Suplied by cervical br of facial nerve
Suture it seperately from skin so it can contract.
Not removed in neck dissections
Elevate the platysma with the skin when making skin flap, staying superficial to the ext/ant jugular veins
- supplies useful blood to overlying skin.

External carotid (63)

Superior thyroid, lingual, facial as per written notes

Occipital artery

From back of external carotid level with facial artery

deep to lower border of posterior belly digastric;

-           grooves base of skull deep to digastric notch on mastoid process

through apex of posterior triangle to back of scalp

-           2 braches to SCM (upper is guide to accessory nerve in front of upper border of that muscle).

At its origin the artery crosses lateral to XII, which hooks around it, looped over by low branch to SCM

Posterior Auricular (63)

Arises above digastric in substance of parotid superficial to styloid process

crosses surface of mastoid process scalp

Auricular branches pinner and ear

Stylomastoid branch stylomastoid foramen facial nerve.

Ascending Pharyngeal

Just above commencement of external carotid from deep up side wall of pharynx deep to ICA

pharyngeal wall and soft palate

meningeal branches through nearby foramina (lacerum, jugular foramen, hypoglossal canal)

Internal Carotid (124,130)

Arises from bifurcation of common carotid up in carotid sheath

Carotid sinus at commencement = small bulge (baroreceptors)

Carotid body behind bifurcation receives 2-3 small glomic arteries (chemoreceptors)

-           carotid body tumours swell at anterior border of SCM at bifurcation

Is lateral to ECA at origin, soon passes posterior medial and deeper

No branches.

Enters carotid canal at base of skull

Relations

Posterior (outside sheath) = symp trunk, pharyngeal veins and superior laryngeal branch of vagus.

Medial = ascending pharyngeal artery

Lateral = IJV, and vagus nerve deep b/n artery and vein

Superficial, near origin, it is crossed by: lingual vain, facial vein (64), occipital artery, XII, and superior root of ansa cervicalis (embedded in the sheath).

Overlapped higher by SCM, and posterior border of digastric, stylohyoid and posterior auricular artery

-           and by those structures separating it from carotid artery (see notes)

Surface Marking

Line from bifurcation of common carotid artery head of mandible.

Surgical Approach

Exposed in neck by incising along anterior border SCM; retracted backwards

-           lingual & facial veins need dividing

-           incise the sheath

Safeguard XII, may need to divide lower SCM branch of occipital artery to allow this.

Can tell difference from ECA by branches on that.


External Jugular Vein
Starts at lower border of lower border of parotid where posterior division of retromandibular vein and posterior auricular vein join.
Descends across SCM deep to platysma on top of deep fascia
Penetrates deep fascia above midpoint of clavicle and joins subclavian.
Tributaries = posteiror external jugular (midway in course) and transverse cervical / suprascapular veins
All join posteriorly
Great auricular nerve runs in a parallel course to its upper third.

Internal Jugular Vein (64)

Emerges from jugular bulb at posterior compartment of jugular foramen.

-           inferior and superior ends have bulbs; inferior bulb has 2 valves

First lies on transverse process of atlas crossed by XI.

Relations

Passes down lateral side of ICA  in sheath (X deep between artery and vein)

Overlaid by SCM in lower part of course.

Deep cervical nodes adjacent through course.

Posterior: cervical plexus (on levator scapulae & scalenus medius) and phrenic on scalenus anterior

-           thoracic duct crosses behind left vein at C7 level.

Anterior: tendon of omohyoid crosses low, heads of SCM at its base

-           inferior root of ansa cervicalis curls around lateral border unites with superior root (from XII) at variable level in front of vein.

Joins subclavian brachiocephalic behind sternal end of clavicle.

Tributaries

First petrosal sinus = first tributary (just below skull base medial to IX,X,XI)

Descending: pharyngeal, lingual, facial, superior and middle thyroid

-           lingual and facial may do so with common trunk (with retromandibular vein and possibly superior thyroid)

Surface Marking

From lobule of ear sternal end of clavicle; b/n 2 heads of SCM

Catheterise b/n two heads of SCM usually

-           direct needle caudally, parallel to sagittal plane entering vein ~4-5cm

Hypoglossal (65)

Emerges b/n ICA and IJV hooks around occipital artery

curves over external carotid and loop of lingual artery (\ crosses 3 arteries)

Then lies just below post belly digastric and above greater horn of hyoid

-           here superior root of ansa cervicalis leaves it

Runs forward on lateral hyoglossus gives of branch to thyrohyoid deep to mylohyoid to mouth.

 

Submandibular Gland / Region (57 in 3rd)


Is deep to cervical fascia, filling submandibular triangle between anterior and posterior bellies of digastric and inferior border of mandible.
Spills over these borders

Digastric

Anterior = from fossa near midline on back of mandible.
- passes backwards and downwards to intermediate tendon held by a fibrous sling to hyoid bone at jx b/n body and greater cornu
- anterior supplied by nervei to mylohyoid
Posterior = passes back and up to its insertion on medial mastoid.
- supplied by branch of facial nerve
- crosses the internal and external carotids, hypoglossal nerve, internal jugular vein, transverse process of atlas and splinal accessory nerve; only facial vein is superficial to it.


M
andibular and Cervical Branches of Facial Nerve

2 lower banches of F n.
often closely related to submandivular gland.

Mandibular branch
exits parotid near angle of mandible, curves up to cross mandible close to facila artery, then supplies lower lip / chin m's.

- usually doesn't lie much lower than inferior border of the mandible; can be 2.5cm below.
--> if divided, get a noticeable facial deformity with depresion of the corner of the lip and drooling.
 
Cevical Br
is  more likely to get damaged
- runs deep to platysma in a down direction, 1-2cm behind angle of mandible.
- at 2cm below angle, it divides; posterior --> platysma; anterior --> corner of mouth

--> division of anterior branch will cause some drooping of the mouth but usally improves with months
- usually doesn't pass >3cm below lower border of mandible.
- so make incisions 4cm or below and through platysma at same level.


The structures superficial to the gland are the facial artery, vein and submental artery and vein.


Facial Vein
Descends across face from inner angle of eye to cross border of mandible ~2cm from its angle.
- lies deep to platysma on the gland.
Submental vein passes back across gland to enter facial vein.
Behind gland, facial vein receives anterior division of retromandibular vein --> passes down as common facial vein --> into IJV
- overlies carotid bifurvation in this course, where it receives the anterior jugular vein from lalong sternomastoid.


Facial
Artery
Arises from external carotid distal to lingual branch and passes up, deep to digastric, to loop over posterior belly in a sigmoid fashion.
Then arches over the posteiror submandibular gland, forming a groove.
Passes forward between gland and medial mandible, then over it to face, making a groove.

- closely related to mandibular branch of facial nerve;gives off largest branch = submental artery --> on mylohyoid.


Muscle Bed of Gland

Most lies on the mylohyoid, but sine oisteruir oirtuib kues ib gtigkissys
- this extends forward deep to mylohyoid with the submandibular duct.
Mylohyoid = from inner mandible to body of hyoid bone, joining in midline raphe
- n. is inferior alveolar br of mandibular division of trigeminal n.
- hypoglossal nerve lies deep to hylohyoid below the deep submandibular gland.
- lingual nerve lies deep tomylohyoid above the deep part of the gland.


Lingual Nerve is a branch of posterior division of mandibular br of trigeminal n.
--> sensation of floor f mouth, side of gums, and anterior 2/3 tongue (latter from chorda tymapani; joins early in its course)
- curves forward on hyoglossus, above deep portion of the gland, passes in a spiral under submandibular duct and up medial side.
- submandibular ganglion hangs off nerve above deep gland.
--> if inflammatory, the nerve can become adherent to the gland and is at risk.

Hyoglossus is from cornu and body of hyoid to insert into tongue.
- separates lingual artery (deep) from hypoglossal nerve (superficial).

- lingual a. gives off sublingual br, runs with hypoglossal.
--> Preserve the sublingual artery with submandibular dissection to safeguard the nerve.


Submandibular ganglion
Secretomotor ganglion of SL and SM glands.
Preganglionic from superior salivatory nucleus --> facial nerve, chorda tympani and lingual.


Subman
dibular Duct
Runs between hylohyoid and hyoglosses, then b/n sublignual gland and genioglossus
Opens at the sublingual papilla.
Reeives ducts from sublingual gland.
Closely related to lingual nerve.


Lymphatics
Immediate nodes are related to the gland by fascial condensations; may be mistaken for gland.
Submental --> submandibular nodes, together with oral cavity nodes and gland itself, which --> deep cervical chain.


Transverse Cervical Bessels