#ff o Cricothyroid muscle (responsible for high pitched voice - fenses vocalfolds) * o tnrertor con,orrctor muscrc I n i U ry : causes loss of high pitched voice.. Suroical Importance: Superior thyroid artery should be ligated as near as possible to the gland to

 

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HEAD & NECK I

Surface Anatomv:

A- ParOtid Gland: connecr the following

4 points:

. Head of the mandible.

o Middle of masseter muscle.

. 2 cm below & behind the angle of

mandible.

o Center of mastoid process.

B-Parotid Duct:

It corresponds to the middle Y" of a horizontal line drawn from the tragus

of the.ear to a point on the upper lip midway between the ala of the

nose and the angle of the mouth.

Points of Suroical Importance:

1-Parotid abscess should be drained by Hilton technique (to avoid injury of

the facial nerveldtt.

2- Frey's syndrome (gustatory syndrome):

- lt follows surgery in the parotid region or tempromandibular joint.

- After injury of auriculotemporal N. post-ganglionic parasympathetic fibers from

otic ganglion become united to sympathetic fibers from superior cervical

ganglion, which supply the vessels & sweat glands of the skin.

- G/P: flushing & sweating of the skln (even with salivation).

JHEAD & NECK

Site: in the digastric triangle, partly below & partly deep to the mandible.

PaftSl superficial part, deep part (in relation to mylohyoid muscle) and submandibular

duct.

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1) Superficial Paft:

Wedge shaped, extending:

. Posteriorly: to the angle of mandible.

. Superiorly.'to mylohyoid line of mandible.

. lnferiorlv: it overlaps the 2 bellies of digastric muscle.

Relations:

o lnfero-lateral surface: related to skin, superficial fascia (containing

platysrna, cervical branch of facial nerve, anterior facial vein and LNs) &

deep fascia.

Lateral su*ace: related to the submandibular fossa of the mandible,

facial artery, my4lohyoid nerve & vessels.

Medial surface: related to 2 muscles (mylohyoid & hyoglossus) & 2

nerves (lingual & hypoglossal).

HEAD & NECK I

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2) Deep Paft:

2- Sympathetic: plexus around the facial artery.

3- Parasympathetic.

&. lt receives secretomor fibers from the submandibular ganglion.

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. Passes through chorda tympani from facial nerve.

LymphatiC Drainaoe: to submandibular & upper deep cervical LNs.

f suroical imDortance:

1f,[f, I is a small part lying deep to mylohyoid & superficial to hyogtossus &

!F between lingual nerve above & hypoglossal nerve below.

3) Submandibular (Wafton's) Duct:

5 cm long. lt has the following course & relations:

o !t arises from the deep part & passes fonruards between mylohyoid

& hyoglossus, having triple relation with the lingual n. (1" lateral to

the n., then below it & finally medialto it).

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Nerve Suoply:

1- Sensory; lingual nerve.

Facial artery should be double ligated during operation for submandibular salivary gland

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. From the floor of the pharynx at the Foramen(aecum

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neck to form both lobes & isthmus.

. From the 4th branchial arch which gives

the superior parathyroid and para-follicular

C cells (neural crest).

Anatomv

o The thyroid is one of the largest endocrine

glands weighing approximately 20 gm &

measuring4x2.5x2cm.

o lt is situated in the neck opposite to the Sth,

6th, & 7th cervical vertebrae.

o Normal thyroid is made up of 2 lobes joined

by thin band of tissues; the isthmus.

Line of descent of thyroid gland

an(track of dryroglossal fistula

Usual position of fryroglossal cyst

Nemal position of &yroid gland

Retrostemal goitr€

o The apex of the lobe lies on the thyroid cartilage below the oblique line while its base

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Capsule of the thvroid gland:

1. True capsule from the stroma of the gland.

2. False capsule from the pretracheal fascia.

Relations:

A) Supefficial Relations:

. Skin, SC tissue, platysma muscle.

o lnvesting layer of deep cervical fascia.

. Sternomastoid muscle (nerve supply: spinal part of Xl cranial nerve).

. Strap muscles (sternothyroid, sternohyoid & omohyoid muscles) ) supplied

by ansa cervicalis from below ) cut the muscles as high as possible.

o Pre-tracheal fascia.

B) Medial Relations:

o Lower oart

Trachea, esophagus with recurrent laryngeal nerve in between.

o Upperpaft

Cricoid and thyroid cartilages, cricothyroid muscle and inferior constrictor

of the pharynx. (i.e. pharynx & larynx).

C) Posterior relutions

Carotid sheath (the carotid artery, the internal jugular vein & the vagus) &

sympathetic chain.

HEAD & NECK I

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Arterial Sunply

1) Superior Thyroid aftery:

o The 1't branch of the external carotid artery.

o lt is related to the external laryngeal nerve (when injured, it leads to loss of high

pitched voice & voice fatigue).

2) lnferior Thyroid artery (inverted L-shaped course):

From the thyro-cervical trunk which is a branch of 1"t part of subclavian artery. Its

terminal branches near the gland are in close relation to recurrent laryngeal nerve

(in between, above or below terminal branches).

3) Thyroida ima artery:

From the arch of aorta or innominate artery (present in 1 - 3o/o of people ) severe

bleeding during thyroidectomy).

4) Accessory Tracheal & Esophageal arteries:

ln ligament of Berry's; which is a thickened part of the pretracheal fascia that joins

trachea to the thyroid gland.

HEAD & NECK I

Venous Drainage

1. Superior Thyroid y,' to internal jugular vein (or

common facial vein).

2. Middle Thyroid vein: crosses common carotid

to join internal jugular vein (middle thyroid vein is

the shortest vein; hence it should be the first vein

to be tied & cut).

3. lnferior Thyroid veins (10-12 veins): pass

from the isth-mus over the iront of the tr-achda to

join the left innominate vein.

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o Peripheral purt:. To the upper & lower

deep cervical lymph nodes.

o Medial ports of both lobes )

1) Pre-laryngeal LNs over cricothyroid membrane (gland of Poirier).

2) Pre-tracheal LNs (Delphi).

3) Deep cervical LNs ) para-tracheal LNs (mediastinal).

Structure of the Thyroid Gland

o lt is formed of follicles lined with cuboidal epithelium (which is the

parenchyma) & vascular CT stroma.

. No basement membrane.

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Oriqin: The nerve arises from the vagus.

I HEAD & NECK

Cou rse:

o The nerve

the left sid

on'the Rt. side turns around the 1" part of Rt. subclavian artery & on

e turns around the arch of the aorta.

o The nerve runs in groove between the trachea & esophagus in close to the

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o lt enters the larynx at the inferior horn of thyroid cartilage.

It SUpplieS: All intrinsic ms of the larynx except cricothvroid muscle (external

laryngeal) & the mucous membrane below the vocal cords.

Surqical importance:

o The nerve might be non recurrent in small percent of cases (2o/o) & in this

situation it might be injured with ligation of the middle thyroid vein.

o Ligation of inferior thyroid artery should be performed away from the gland to

to the nerve.

NB: Fibers of the adductors are in the middle of the recunent laryngeal n. while the

fibers of abductors are in the periphery.

O riO i n : ft arises from the superior laryngeal n. of the vagus.

COU rSe: lt passes in close relation to .g.Up.efjp.t.thyf.q.id..af.tS.fy. It supplies:

#ff o Cricothyroid muscle (responsible for high pitched voice - fenses vocalfolds) * o tnrertor con,orrctor muscrc

I n i U ry : causes loss of high pitched voice..

Suroical Importance:

Superior thyroid artery should be ligated as near as possible to the gland to

avoid injury of the nerve.

HEAD & NECK I

Embryoloqv:

Anatomy: They are 4 in number

. Size: each gland is about 0.5 cm.

. Color yellowish brown.

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