Neck

(Visceral region)

Dra. Andrea Rila E. Pera

 Table of Contents

1 Endocrine
2 Respiratory
3 Digestive

● Thyroid ● Larynx ● Laryngopharynx

● Parathyroid ● Cervical Trachea ● Cervical Esophagus

Endocrine layer

● Thyroid gland

● Parathyroid gland
Thyroid gland
- below and lateral the thyroid cartilage
- 2 lobes connected by an isthmus
- covered by pretracheal layer
- produces thyroxine and triiodothyronine (increase the
metabolic activity of most cells in the body) and
thyrocalcitonin (lowers the level of blood calcium)
 Development of thyroid gland:
The thyroid gland arises as a median
outgrowth from the floor of the pharynx near
the base of the tongue.

● foramen cecum of the tongue- indicates

the site of origin
● thyroglossal duct - path of migration of
the thyroid gland to its final adult
location; usually disappears early in
development
Ectopic thyroid gland or remnants which can
be functional:

■ Lingual thyroid- associated with the tongue

■ Pyramidal lobe- extending upward from
the gland along the path of the
thyroglossal duct
- if present, connected by a fibrous or
muscular band (levator glandulae
thyroideae)
■ Anywhere along the path of migration of
the thyroid gland
Parts of the thyroid gland:

Lobes: right and left

- pear- shaped
- apex: oblique line of the thyroid cartilage
- base: below 4th or 5th tracheal rings

Isthmus- connecting the lobes

- 2nd-4th tracheal rings
 Relations of the lobes:

■ Anterolateral: The sternothyroid, the

superior belly of the omohyoid, the
sternohyoid, and the anterior border
of the sternocleidomastoid
■ Posterolateral: The carotid sheath (CCA,
IJV, VN)
■ Medial: The larynx, the trachea, the
pharynx, and the esophagus,
cricothyroid muscle, external
laryngeal nerve, recurrent laryngeal nerve
Relations of the Isthmus: ■ Posterior of each lobe: superior and inferior
parathyroid glands and the anastomosis
■ Anterior: sternothyroids, sternohyoids, anterior between the superior and inferior thyroid
jugular veins, fascia, and skin arteries
■ Posterior: tracheal rings 2-4
■ Upper border: anastomosis of the terminal
branches of the superior thyroid arteries
Parathyroid
gland
- ovoid bodies measuring about 6 mm long in their
greatest diameter.
- four in number and are closely related to the posterior
border of the thyroid gland
- produces parathyroid hormone (increases the calcium
levels in the blood and diminishes the reabsorption of
phosphate in the kidney)
Position of the parathyroid gland:

* superior parathyroid- constantly at the

middle of the posterior border of the thyroid
* inferior parathyroid- usually at the level of
the inferior pole, but can be ectopic up to the
superior mediastinum
Respiratory layer

● Larynx
● Cervical trachea
 Larynx
- a hollow musculoligamentous structure
- start of LRT
- both a valve (or sphincter) to close the lower respiratory
tract, and an instrument to produce
sound
- during swallowing, the dramatic upward and forward
movements of the larynx facilititate closing the laryngeal inlet
and opening the esophagus
● Laryngeal cartilages
3 unpaired, larger
* cricoid
* thyroid
* epiglottis
3 paired, smaller
* arytenoid
* corniculate
* cuneiform
● Ligaments (extrinsic and intrinsic)
● Laryngeal joints
● Cavity
● Intrinsic Muscles
 Unpaired laryngeal cartilages

Cricoid c. Thyroid c. Epiglottis

● signet ring ● largest ● leaf-shaped
● most inferior ● lamina, laryngeal prominence (90 deg in men- ● epiglottic tubercle
● lamina, arch, ridge, Adam’s apple), sup thyroid notch, inf thyroid (posterior surface)
depression, 2 pairs of notch, superior horn, inferior horn, oblique line
articular facets (sup and inf thyroid tubercles)
 Paired laryngeal cartilages

Arytenoid c. Corniculate c. Cuneiform c.

● pyramid ● conical/cone ● rod/club
● apex, base, 3 surfaces ● apex: posteromedial ● suspended in the
(anterolateral, medial, ● base: with arytenoid c. fibroelastic membrane
posterior), vocal process
(aryepiglottic folds)
 Extrinsic laryngeal ligaments

● Thyrohyoid membrane- thyroid cartilage to

hyoid bone
- has lateral aperture (sla and int sln and
lymphatics), lateral t-h ligament, median t-h lig
+/- triticeal cart

● Hyo-epiglottic l.- median epiglottis to hyoid

bone

● Cricotracheal l.- cricoid to 1st tracheal ring

 Intrinsic laryngeal ligaments

- fibroelastic membrane that links the laryngeal cartilages

together

● conus elasticus (cricovocal membrane)- lower;

cricoid cartilage to free upper margin inside the
thyroid cartilage
* free upper margin= vocal ligament (under the
vocal fold/true vocal cord)
- anteriorly to the thyroid cart, posteriorly to
the vocal process of arytenoid cart
* median cricothyroid ligament- thickening in the
anterior midline under the inf thyroid notch up to the
attachment of vocal lig
● Quadrangular membrane- epiglottis (lateral) to
arytenoid and corniculate cartilages with free
upper and lower margins

* free lower margin= vestibular ligament (under

vestibular fold/false vocal cord)
- anteriorly to the thyroid angle superior to
the attachment of the vocal ligament, posteriorly to
the anterolateral surface of the arytenoid (vest lig is
more lateral to vocal lig when viewed from above)
 Laryngeal joints

Cricothyroid j. Cricoarytenoid j.
● synovial joint ● synovial joint
● inferior horn of the thyroid cart and the cricoid cart ● superolateral surfaces of the cricoid and the base of the
● allows forward and downward movement of the tc to th arytenoid
cc (lengthens and tenses the vocal lig) ● enable the arytenoid cartilages to slide and to rotate
(abduction and adduction of vocal lig)
Laryngeal Cavity

- tubular, lined by mucosa

● Superior aperture/laryngeal inlet- opens to the anterior

pharynx; oblique; can be closed by downward movement
of the epiglottis
Boundaries
anterior: mucosa covering the
superior margin of the epiglottis
lateral: aryepiglottic folds and piriform fossa (recess on
either sides)
posterolateral: two tubercles (cuneiform and corniculate
cartilages)
posterior midline: interarytenoid notc (between the two
corniculate tubercles)

● Inferior aperture- continuously open with the trachea,

encircled by the cricoid cartilage; horizontal
3 major divisions of the laryngeal cavity:

■ vestibule/supraglottic- upper chamber of the

laryngeal cavity between the laryngeal inlet and
the vestibular folds
■ middle part/glottic/transglottic- between the
vestibular folds and the vocal folds

■ infraglottic/subglottic space- the most inferior

chamber, between the vocal folds and the
inferior opening of the larynx.
 Other parts of the cavity:

● Laryngeal ventricles- trough-shaped space in

the lateral surface of the gap between vest and
vocal lig
● Laryngeal saccules- tubular extension of each
ventricles projecting anterosuperiorly to the
thyroid cart; with mucus glands to lubricate
vocal folds
● Rima vestibuli- triangular opening between
the 2 vest lig
● Rima glottidis- narrower triangular opening
between the 2 vocal lig (base: intraarytenoid
fold- bottom of intraarytenoid notch)
Muscles of the Larynx

Intrinsic
- modifying laryngeal inlet
(widening and narrowing)
- move the vocal cords/folds
(tensing, relaxing, abduct and
adduct)

Extrinsic
- for swallowing (moving the larynx
up and down through the hyoid
bone via thyrohyoid membrane;
closing the inlet)
 Intrinsic Muscles of the Larynx
(Controlling the laryngeal inlet)

Oblique arytenoids
● muscular process on the post arytenoid cart--
>apex of opposite arytenoid cart
● ary-epiglottic part- lateral continuation to the
aryepiglottic fold
● narrowing the inlet

Thyroarytenoid (thyroepiglottic part)

● part of thyroaytenoid muscle

● lateral part of the aryepiglottic fold-->margins of epiglottis
● pulls the arytenoid cartilages forward while simultaneously
pulling the epiglottis toward the arytenoid cartilages.
 Intrinsic Muscles of the Larynx
(Controlling the movements of vocal cords/folds)

Cricothyroid
● anterolateral cricoid-->thyroid cart
* oblique part- arch of cricoid--> inf horn
* straight part- arch--> posteroinferior margin of the thyroid lamina
● pulls the thyroid cart forward and down (lengthens the vc)
● only int musc supplied by the SLN of CNX (Vagus)

Thyroarytenoid (vocalis muscle)

● part of thyroaytenoid muscle

● elongated muscles lateral to and running parallel with each vocal
ligament
● anterolateral arytenoid-->thyroid angle
● adjust tension in the vocal folds
 Intrinsic Muscles of the Larynx
(Controlling the movements of vocal cords/folds)

Cricoarytenoid (Lateral and Posterior)

● Posterior- posterior cricoid cartilage-->muscular processes of the arytenoid
cartilage; abduct and externally (laterally) rotate the arytenoid cartilages,
thereby opening the rima glottidis (primary abductors)
● Lateral- upper surface of the arch of the cricoid-->muscular process of the
arytenoid cartilage; internal rotation and adduction

Transverse arytenoid

● arytenoids-->opposite arytenoids
● adductors of arytenoids/vc
 Functions of the Larynx

● Effort closure- needed when air should be

● Respiration:
retained in the thoracic cavity to stabilize
Quiet- open inlet, abducted ac, triangular
the trunk and increase intraabdominal
rima glottidis
pressure (heavy lifting)
Forced inspiration- wide open, lateral
- closed rg, rv and lower parts of the
rotation and abducted ac, rhomboid rg
vestibule
● Phonation- adducted ac and vc, closed
rg (to vibrate with each other);
● Swallowing- closed rg, rv and vestibule
modification of sound by tensing the vc
plus narrowed inlet; larynx moves up and
forward (closure of the inlet and opening
of the esophagus posteriorly)
Cervical Trachea
-mobile cartilaginous and membranous tube
- with U-shaped hyalin cartilages (tracheal rings) and posterior
smooth muscle (trachealis muscle)
- approx 5cm/5 tracheal rings (Cv6-Cv7/ inferior cricoid-
suprasternal notch) out of the total 11-12cm/18-22 tracheal rings
length of the trachea
Relations of the Trachea in the Neck:

■ Anteriorly: Skin, fascia, isthmus of the thyroid

gland, inferior
thyroid vein, jugular arch, thyroidea ima artery
(if present), and the left brachiocephalic vein in
children, overlapped by the sternothyroid and
sternohyoid muscles
■ Posteriorly: Right and left recurrent laryngeal
nerves and the esophagus
■ Laterally: Lobes of the thyroid gland and the
carotid sheath and contents
 Digestive layer

● Pharynx (laryngo/hypopharynx)
● Cervical Esophagus
Pharynx
(laryngopharynx)
- superior margin of the epiglottis (Cv4) to the top of the esophagus
(Cv6) or (hyoid bone-->cricoid cart)
 3 anatomical subsites:

● piriform fossa/pyriform sinus- pair of mucosal recesses between the

larynx and the lamina of the thyroid cartilage; lateral
- channels that direct solids and liquids from the oral cavity
around the raised laryngeal inlet into the esophagus (smuggler’s fossa)

● postcricoid area- anterior wall of hypopharynx; entire cricoid

cartilage

● post pharyngeal wall- hyoid to cricoarytenoid joint

-mucosa and constrictor muscles (middle and inferior constrictors)
- cricopharyngeus muscle: most distal inferior constrictor; constitutes
the UES
- Killian’s dehiscence : between the upper propulsive part of the
inferior constrictor and the lower sphincteric part ( cricopharyngeus)
Layers of the pharyngeal wall (from within
outwards): MIMO

1. Mucous coat
2. Inner fibrous coat (pharyngobasilar fascia)
3. Muscular coat
4. Outer fibrous coat (buccopharyngeal
fascia)
Cervical esophagus
- posterior to the trachea and thyroid gland
- inferior border of the cricoid cartilage (opposite C6
vertebra) to the level of the thoracic inlet (opposite T1
vertebra)
- approx 5cm (out of 22-28cm) in adult

Upper Esophageal Sphincter- cricopharyngeus muscle

Relations of the esophagus in the neck:

- deviates to the left in the inferior aspect of the neck

Anterior: trachea, thyroid gland; RLN and pretracheal fascia
Lateral: B: CCA and RLN; Left: Thoracic duct
Posterior: Cv6 to Tv1 (thoracic inlet), longus colli muscles
and prevertebral fascia

Esophageal wall from inside out:

1. mucosal
2. submucosal
3. muscular (ICOL)- internal: circular (cricopharyngeus)
- outer: longitudinal (wall of hypopharynx)
4. external fibrous
Function:
Swallowing (esophageal stage)- starts once food is transferred from the oral cavity to the UES
- active process (conscious): contractions of muscular layer (ICOL) + relaxation of LES
- esophageal peristalsis: CNX (Vagus)
Patterns of peristalsis:

1. Primary- central mechanism; circular wave contractions pushing down the food until it reaches the relaxed LES
2. Secondary- not central; contractions in resposnse to distention; for clearance
3. Tertiary- non peristaltic contractions
Thank you!
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