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Table 5.1 Pharyngeal muscles
Muscle name
Tensor veli palatini Medial pterygoid
Levator veli palatini The petrous part of
Palatoglossus Palatine
Palatopharyngeus Palatine
Styloglossus Styloid process of
Genioglossus The superior part
Hyoglossus Hyoid Side of the tongue Moves tongue
Salpingopharyngeus The lower part of
Stylopharyngeus Styloid process Thyroid cartilage Moves
Constrictor
pharyngis superior
Constrictor
pharyngis medius
Origin Insertion Function
Palatine
plate of the
sphenoid bone
the temporal bone,
the cartilaginous
part of the auditory
tube
aponeurosis
aponeurosis and
hard palate
temporal bone
of the mental spine
of the mandible
the cartilage of the
auditory tube
Medial pterygoid
plate,
pterygomandibular
raphe, alveolar
process
Hyoid bone Pharyngeal raphe Stiffens
aponeurosis
Palatine
aponeurosis
Tongue Moves tongue
The upper border
of thyroid
cartilage
Tip and sides of
the tongue
Underside of
tongue and body
of hyoid
Blends with
palatopharyngeus
muscle
Pharyngeal raphe,
pharyngeal
tubercle
Moves soft
palate up and
posterior
Moves soft
palate up
up and
posterior
Moves soft
palate down,
pharynx up
Moves tongue
up and
posterior
Moves tongue
down and
anterior
down and
posterior
Elevates
pharynx, opens
auditory tube
during
swallowing
pharynx up
and widens it
Stiffens
posterior
pharyngeal
wall, reduces
pharyngeal
lumen,
swallowing
posterior
pharyngeal
wall, reduces
pharyngeal
lumen, pulls
hyoid
backward,
swallowing
M. Delakorda
Innervation
V
V
XII
XI
XII
XII
XII
X
IX
X
X
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Table 5.1 (continued)
Muscle name
Constrictor
pharyngis inferior
Digastric v. anterior Digastric fossa of
Digastric v.
posterior
Geniohyoideus Inferior mental
Stylohyoideus Styloid process Greater cornu of
Mylohyoideus Mylohyoid line of
Omohyoideus Inferior belly:
Thyrohyoideus Oblique line of the
Sternohyoideus Manubrium of
Sternothyroideus The posterior
Crycothyroideus Anterolateral part
Origin Insertion Function
Thyropharyngeal
part: Oblique line
of thyroid cartilage
Cricopharyngeal
part: Cricoid
cartilage
mandible
The mastoid notch
of the temporal
bone
spine of mandible
mandible
Superior border of
scapula near the
suprascapular
notch
Superior belly:
Intermediate
tendon
thyroid cartilage
sternum, medial
end of clavicle
surface of the
manubrium of the
sternum, costal
cartilage of rib 1
of cricoid cartilage
Thyropharyngeal
part: Median
pharyngeal raphe
Cricopharyngeal
part: Blends
inferiorly with
circular
esophageal bers
Body of hyoid
bone
Body of hyoid
bone
Body of hyoid
bone
the hyoid bone
Body of hyoid
bone and median
ridge
Inferior belly:
Intermediate
tendon
Superior belly:
the body of the
hyoid bone
Greater horn of
the hyoid bone
The inferior
border of the
body of the hyoid
bone
Oblique line of
thyroid cartilage
Oblique part:
Inferior horn of
thyroid cartilage
Straight part:
Inferior margin of
thyroid cartilage
Stiffens
posterior
pharyngeal
wall, reduces
pharyngeal
lumen,
sphincteric
function,
swallowing
Moves hyoid
anterior
Moves hyoid
posterior
Moves tongue
and hyoid up
Moves hyoid
up and
posterior
Stiffens oor
of the mouth
Moves hyoid
down
Approximates
hyoid in
thyoroid
Moves hyoid
down
Moves thyorid
down
Tenses vocal
cords
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Innervation
X
VII
V
XII
VII
V
C1–3 via
XII
C1–3 via
XII
C1–3 via
XII
C1–3 via
XII
X
(continued)
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Table 5.1 (continued)
Muscle name
Crycoarytenoideus
posterior
Crycoarytenoideus
lateralis
Arytenoideus
transversus
Arytenoideus
obliquus
Thyroarytenoideus The angle of the
Vocalis Lateral surface of
Aryepiglotticus Apex of arytenoid The lateral border
Origin Insertion Function
The posterior part
of the cricoid
The lateral part of
the arch of the
cricoid
Arytenoid cartilage
on one side
Posterior surface of
muscular process
of arytenoid
cartilage
thyroid cartilage
and adjacent
cricothyroid
ligament
vocal processes of
arytenoid cartilage
Posterior surface
of muscular
process of the
arytenoid
cartilage
Muscular process
of the arytenoid
cartilage
Arytenoid
cartilage on the
opposite side
The posterior
surface of the
apex of the
adjacent arytenoid
cartilage extends
into the
aryepiglottic fold
The anterolateral
surface of
arytenoid
cartilage
Anterior part of
ipsilateral vocal
ligament
of the epiglottis
M. Delakorda
Abducts and
laterally
rotates
arytenoid
cartilage,
pulling vocal
ligaments
away from the
midline and
forward and
opening rima
glottidis
Adducts and
medially
rotates the
cartilage,
pulling the
vocal
ligaments
towards the
midline and
backwards and
so closing off
the rima
glottidis
Approximates
the arytenoid
cartilages
Sphincter of
the laryngeal
inlet
Relaxes vocal
cords
Tenses anterior
part and
relaxes
posterior part
of vocal
ligament
Closes the inlet X
Innervation
X
X
X
X
X
X
(continued)
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Table 5.1 (continued)
Muscle name
Thyroepiglotticus The inner surface
Origin Insertion Function
Aryepiglottic fold
of the thyroid
cartilage is in
common with the
thyroarytenoideus
muscle
and margin of
epiglottis
Depresses base
of epiglottis
Innervation
X
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internal longitudinal muscles (the stylopharyngeal, palatopharyngeal, and salpingopharyngeal muscles). It has been established that the activity of the three external
circular muscles, which mutually overlap, produces a sphincteric and peristaltic
action and that the three internal longitudinal muscles elevate the pharynx and larynx. The muscles attached to the epiglottis are weak and do not have much effect on
its position [29]. Therefore, it depends mainly on the surrounding structures to
which the epiglottis is attached by a complex suspension apparatus. Among them,
the anterior ligaments that connect the epiglottis to the tongue and the hyoid bone
are probably the most important for the movement and its shape [16]. The position
of the epiglottis also depends on the relationship between the thyroid cartilage and
the hyoid bone, and the position of the tongue base, which is related to the activity
of the m. genioglossus, the main pharyngeal dilator.
The soft palate is composed of several integrated muscles: palatopharyngeus,
palatoglossus, levator veli palatini, tensor veli palatini, and musculus uvulae. They
control the stiffness and position of the palate, tongue, and pharynx. As such, these
muscles are important in the maintenance of UA patency, and a comprehensive
understanding of their action is necessary for successful surgical procedures of the
soft palate and the lateral pharyngeal walls. The tensor palatini muscle makes the
soft palate more rigid. Together with the levator palatini, which is an antagonist of
the palatopharyngeus, it enables its proper functioning. The palatopharyngeal muscle originates from either the superior (nasal) or inferior (oral) surface of the palatine aponeurosis or the medial part of the soft palate. In its upper course, it has
vertically and horizontally oriented bers. After forming the palatopharyngeal arch,
the palatopharyngeus continues infero-posteriorly toward the lateral part of the epiglottis spreading radially on the inner aspect of the pharyngeal wall, merging with
the salpingopharyngeal and stylopharyngeal muscles. In most cases, the palatopharyngeus does not attach to the epiglottis but is in continuation with the sparse bers
of the aryepiglottic muscle [16]. From here, it passes behind the arytenoids as the
continuation of the oblique arytenoids attaching to the posterior surface of the contralateral arytenoid cartilage. In its inferior part, the aryepiglottic muscle bers continue and connect to the inner surface of the inferior pharyngeal constrictor where
they help with opening the upper esophageal sphincter by pulling it in the superolateral direction [35]. It is believed that the palatopharyngeus muscle acts as a
sphincter encircling the pharyngeal isthmus. It also holds the epiglottis in contact
with the soft palate, providing a direct air channel from the nose to the larynx in
newborns [36]. In about 25% of cases, the descending longitudinal muscles of the
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palatopharyngeus insert into the epiglottis and contribute to the formation of the
pharyngoepiglottic fold [37–39]. According to an anatomic study performed by
Vandaele etal., the only muscle bers that consistently insert into the epiglottis are
the continuation of the thyroarytenoid muscle; alternatively, they may originate
from the anterolateral surface of the arytenoid cartilage as distinct muscle bundles.
They are all attached to the epiglottic petiolus and contribute to the narrowing of the
laryngeal vestibule [16]. All other muscles affect the position and movement of the
epiglottis indirectly, through the movement of structures to which the epiglottis is
attached by ligaments or membranes.
Because of its role in OSA pathogenesis, the genioglossus muscle (GG) is
probably the most extensively studied UA dilator muscle. It is an extrinsic tongue
muscle and the largest of the pharyngeal dilator muscles. The GG originates from
the mental spine of the mandible and fans out with a bulk of bers inserted into
the body of the tongue. The lowermost bers extend backward and downward into
the hyoid bone, while the uppermost bers extend upward and anteriorly into the
tip of the tongue. [40] Its function is to move the tongue downward and anteriorly,
thus widening the retroglossal space. The thyrohyoid, geniohyoid, and mylohyoid
muscles are believed to be the primary effectors of anterior hyoid bone movement
and thus are the principal muscles affecting epiglottic movements and position
[41]. Based on structural properties, the geniohyoid muscle has the most potential
to displace the hyoid in the anterior direction, and the mylohyoid has the most
potential to displace the hyoid in the superior direction [42]. Other muscles such
as the anterior belly of the digastric contribute less to the anterior motion of the
hyoid [43].
OSA is thought to be associated with changes in the contractile properties of UA
muscles. Several studies have shown remodeling of the UA muscles in patients with
OSA with an increase in type II fast-twitch bers that are more likely to fatigue than
type I bers, making patients with OSA more susceptible to fatigue than those of
normal subjects [44–46].
M. Delakorda
5.7 Blood Vessels andLymphatics
Sound knowledge of the vascular supply is important in order to avoid damage to
major blood vessels during surgery, which may cause life-threatening complications due to potential aspiration and hypoxia. ENT surgeons undertaking surgery in
the pharyngeal and supraglottic region must be aware that bleeding complications
during endoscopic procedures are potentially more problematic than those in traditional open surgery [47].
The arterial blood supply to the supraglottic larynx comes mainly from the
superior laryngeal artery (SLA). Usually, it is a branch of the superior thyroid
artery, but in about one-third of the cases, it originates directly from the external
carotid artery above the superior thyroid artery [9, 48]. From its origin, it passes
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horizontally toward the posterior portion of the thyrohyoid membrane together
with the internal branch of the superior laryngeal nerve (SLN) and pierces the
membrane below the nerve, anterior to the superior cornu of the thyroid cartilage,
to enter the larynx. Here, it runs between the intrinsic laryngeal muscles and thyroid cartilage in the PGS and splits into several ascending and descending branches.
An “aberrant” SLA is present in up to 20% of larynx dissections. It enters the PGS
through the thyroid foramen in the posterior portion of the thyroid cartilage lamina; the same foramen can also serve as a passage for anastomosis of the external
and internal laryngeal nerves [49]. Even in such cases, the intralaryngeal branching
is similar to the normal SLA [48, 50]. The ascending branch runs upward tortuously until the level of the pharyngoepiglottic fold where it splits into smaller vessels. The most relevant for epiglottic surgery are the superior and anterior branches.
The superior branch runs supercially on the lingual surface of the epiglottis and
valleculae where it forms a vascular network with the dorsal branches of the lingual artery (Fig.5.3). Some vessels from this plexus reach the upper part of the
epiglottis and run over its edge or pierce the cartilage. The anterior branch runs
toward the superior border of the thyroid cartilage and laryngeal prominence supplying the laryngeal ventricle. Collateral branches fan out of the ascending branch
toward the lower half of the epiglottis cartilage, reaching its dorsal surface through
Fig. 5.3 Stereographic angiograms of the larynx with the surrounding tissue. The superior laryngeal artery (SLA), derived from the superior thyroid artery (STA), splits into ascending (Abr) and
descending branches (Dbr). 1 base of the tongue, 2 epiglottis (dotted circle), 3 vestibular fold, 4
vocal fold, 6 trachea, LA lingual artery, left: small black arrows distal portions of the superior
thyroid artery, right: small white arrows inferior vessels of Abr, and small black arrows superior
vessels of Abr. (Adapted from Ref. [51]. Source: https://www.jstage.jst.go.jp/article/
ofaj/86/2/86_2_61/_article/- char/en)
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M. Delakorda
the aryepiglottic fold [48, 51]. The descending branch turns its course inferiorly
approximately 1cm anterior to the base of the superior horn of thyroid cartilage
and continues deep to the thyroid cartilage lamina in the PGS, ending at the superior border of the lateral cricoarytenoid muscle. At this level, the anterior terminal
branches anastomose with the cricothyroid artery and the posterior branches anastomose with the inferior laryngeal artery.
The lingual artery is the second branch of the external carotid artery from
which it branches at the level of the hyoid bone. It courses laterally to the middle
pharyngeal constrictor muscle where it is crossed by the hypoglossal nerve, and
then, it passes deep to the hyoglossus muscle where it runs on the superior surface
of the hyoid bone. It is this location where it is vulnerable to injury during transoral tongue base surgery. The lingual artery then gives off a suprahyoid branch,
a dorsal lingual artery that passes to the dorsum of the tongue, the sublingual
artery, and the deep lingual artery that passes between the genioglossus muscle
and the inferior intrinsic tongue musculature [52]. Throughout the larynx, including the epiglottis, there is an abundant arterial anastomotic network with bilateral
perfusion [53].
The laryngeal veins accompany the arteries and drain into the superior thyroid
and inferior thyroid veins that drain into the internal jugular and the subclavian
veins, respectively [52]. The tongue is drained by lingual veins that pass to the internal jugular vein directly or via the facial and retromandibular veins. Laryngeal lymphatics are numerous, except over the area of the true vocal cords. Due to different
developmental origins, supraglottic and infraglottic regions drain separately and no
lymphatic communication exists between these two regions. Lymphatic vessels of
the supraglottic area are very dense and run through the oor of the piriform sinus
with the SLA, and drain into the upper jugular nodes [9].
With the advancement of endoscopic approaches, there was also a need to understand the anatomy from an “inside-out” perspective, i.e., to visualize the structures
as they are encountered when approaching through the lumen of the upper respiratory tract. Important work in this area has been done by robotic surgery instructors
[52]. Due to the variability between individuals, most anatomical landmarks are
unreliable, and a surgeon must rely on a meticulous and careful technique of tissue
preparation. In the case of tongue-based surgery, special care should be taken due to
the proximity of the larger branches of the lingual artery that can get medialized
because of outward tongue retraction. Most authors agree that it is possible to avoid
contact with the hypoglossal-lingual artery neurovascular bundle if the dissection is
carried out within 1.5 cm from the midline [54]. During endoscopic preparation
close to the lateral wall, the main trunk of the intralaryngeal SLA can be identied
just inferior to the greater cornu of the hyoid bone in the PGS, right after piercing
the thyrohyoid membrane (Fig.5.4) [55].
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Fig. 5.4 Endoscopic view
of supraglottic anatomy. A
superior laryngeal bundle,
LA lingual artery, DLA
dorsal lingual artery, E
epiglottis, H hyoid bone,
and HGM hyoglossal
muscle
5.8 Innervation
75
Most muscles of the pharynx, including the soft palate, receive motor innervation
from the pharyngeal plexus overlying the posterior surface of the middle pharyngeal
constrictor. This structure’s detailed anatomy and functional mechanism are still not
entirely understood [56]. It is formed by pharyngeal branches of the glossopharyngeal and vagal nerve, and sympathetic bers from the superior cervical ganglion.
The pharyngeal branches of the vagal nerve provide motor innervation to most muscles of the pharynx and palate, except the stylopharyngeus muscle and the tensor
veli palatini muscle, which are supplied by the glossopharyngeal nerve and the
mandibular branch of the trigeminal nerve, respectively. All tongue muscles except
for the palatoglossus muscle, which is innervated by the glossopharyngeal nerve,
are innervated by the hypoglossal nerve [52].
The larynx is supplied by the vagal laryngeal branches, the superior laryngeal
nerve (SLN), and the recurrent laryngeal nerve (RLN). The SLN arises from the
inferior (nodose) ganglion of the vagal nerve, and it is accompanied by branches
from the superior cervical ganglion of the sympathetic trunk. After descending
between the carotid arteries and the pharyngeal wall, it reaches the larynx and splits
into an internal and external branch just below the hyoid bone. The external branch
runs close to the superior thyroid artery and provides motor innervation to the inferior constrictor and cricothyroid muscle. The internal branch passes the thyrohyoid
membrane with the SLA and splits into several branches. The upper branches provide sensation to the epiglottis, valleculae, laryngeal vestibule, and vestibular (false
vocal) folds, while the lower branches provide sensation to mucosa below the
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vestibule and the pyriform sinuses. Preserving the lower branches during surgical
resection spares sensory innervation to the hypopharynx and larynx below the vestibule, which is important to avoid aspiration [52]. The RLN provides motor innervation to all intrinsic muscles of the larynx except the cricothyroid muscle as well
as sensation to the vocal folds and the subglottis.
Muscles attaching to the hyoid have a heterogeneous innervation, and precise
motor control differs for each one. The mylohyoid muscle and anterior belly of
digastric muscles are innervated by the mandibular division of the trigeminal nerve.
Motor innervation of the stylohyoid muscles and the posterior belly of digastric
muscles is provided by the facial nerve. Motor innervation to the infrahyoid muscles
comes from the ansa cervicalis. The activity of the geniohyoid, mylohyoid, and
sternohyoid are reported to change with respiration (Table5.1) [57].
Throughout the UA, the mucosal lining is richly supplied with a dense plexus of
nerve bers that is in close association with the epithelium. Sensory nerve terminals, heterogenous in their embryological origin and functionality, are essential for
respiratory regulation and lower airway protection. They can be associated with
different terminal structures within the airway wall, such as mucosal glands, vasculature, or smooth muscles, or they can end as free nerve endings in mucosal, submucosal, or parenchymal tissues [58]. The posterior epiglottic surface is perforated by
branches of the internal laryngeal nerve and brous tissue, so the posterior, i.e.,
laryngeal surface of the epiglottis, is in continuity through these perforations with
the pre-epiglottic space.
M. Delakorda
5.9 Mucosa
The mucosa of the UA is not just a uniform and homogeneous tube for gas transmission and exchange, but a complex and heterogeneous organic system that allows
monitoring of the air environment and physiological responses to changes in it [59].
Most of the larynx, including the posterior surface of the epiglottis, is covered by a
ciliated, pseudostratied respiratory epithelium that provides a ciliary clearance
mechanism shared with most of the respiratory tract. The anterior surface of the
epiglottis is covered by non-keratinized, stratied squamous epithelium protecting
the underlying tissues from mechanical stress [13]. The transition zone between
both epithelia is located at the lower half of the posterior surface of the epiglottis,
medial to the aryepiglottic folds [9]. The epiglottic epithelium is reected onto the
base of the tongue and the lateral pharyngeal walls as a medial glossoepiglottic, and
two lateral glossoepiglottic (pharyngoepiglottic) folds. The submucosal tissue of
the epiglottis is fascial and continuous laterally with the internal pharyngeal fascia
overlying the middle and inferior constrictor muscles and medially with the submucosa of the laryngeal vestibule. Superiorly, it is continuous with the submucosa of
the tongue [16].
In the squamous epithelium of the epiglottis, aryepiglottic folds, arytenoid
regions, the interarytenoid notch, and the membranous portion of the vocal folds,
the Langerhans cells are present [33]. These tissue-resident macrophages are an
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important part of the human immune system. As a part of the dendritic antigenpresenting system, they have an ability to capture antigens and initiate T cellmediated immunity, which is essential for the defense of the UA mucosa [60, 61].
Laryngeal secretions also contain IgG, IgA, and IgE antibodies and lactoferrin, all
important in the local immune system [62]. The posterior surface of the epiglottis
cartilage is pitted by small mucous glands. Like other secretory glands in the UA,
they produce a liquid lining of the respiratory epithelium consisting of a periciliary
liquid layer and a supercial mucous component. Its properties, i.e., thickness and
viscosity, inuence surface tension and wall shear stress. Additionally, they appear
to have an effect on the response of the pharyngeal dilator muscles to stimulation of
the mechanoreceptors and thus pharyngeal collapsibility [63]. Overstimulation of
UA secretion makes a collapsed airway more difcult to open, while application of
the substances with surface tension-lowering properties is associated with a reduction in airow resistance [64]. Age-related changes in the laryngeal glands inuence
the local immunity and mucociliary transport of the larynx. The concentration of
laryngeal glands decreases with age; moreover, the ratio of mucous versus serous
glands tends to increase. This affects not only the amount but also the quality and
viscosity of secretions. A similar effect can be observed in the laryngeal mucosa of
irradiated patients [33, 65, 66].
The larynx is a highly reexogenic area with many different types of receptors
that respond to mechanical and chemical stimuli. Sensory information from the
UA is transmitted by the trigeminal, glossopharyngeal, and internal branches of
the SLN [67]. While the role of reex arches in the protective mechanism against
aspiration has been extensively researched, their role in OSA pathogenesis has not
been denitively elucidated. Chemoreceptors similar to taste buds of the tongue
are found on the epithelium of the soft palate, aryepiglottic folds, and laryngeal
surfaces of the epiglottis. They are adapted for the detection of chemicals that are
not saline-like in composition and thus do not respond to normal mucus secretions.
Electrophysiological recordings from SLN bers in response to stimulation of the
epiglottis have demonstrated the highest response to NaCl solutions higher or lower
than saline with a U-shaped response-concentration function [68–70]. Accordingly,
their role is not the gustation but prevention of aspiration of food and liquids [71,
72]. Morphologically diverse and highly sensitive mechanoreceptors are located
within the UA mucosa, near muscles, and joints [73]. Recordings from their afferent
bers have revealed that some of them are spontaneously active whereas others are
silent until stimulated. They respond to negative pressure, mechanical deformation,
and high- frequency vibrations, like those generated during snoring. [67, 74, 75] The
majority are located in the nose, larynx, and upper trachea. Their effect is abolished
when topical anesthetic is applied and may be altered after radiotherapy of the neck.
Efferent actions include alterations in the rate and depth of breathing as well as
increasing or decreasing autonomic ow to the airway’s smooth muscle, glands, and
vasculature [76]. Moreover, these reex arches regulate the response of the pharyngeal dilator muscles, a mechanism that mediates the increased genioglossal activity
observed in patients with inadequate pharyngeal anatomy during wakefulness. How
these mechanisms are modulated by sleep is just beginning to be understood, but
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