complete feeding sequences on foods of different initial consistency. Sade J (ed) 1989 Basic Aspects of the Eustachian Tube and Middle Ear
Dysphagia 14:31–42. Disease. Geneva: Kugler & Ghedini.
Hiiemae KM, Palmer JB 2003 Tongue movements in feeding and speech. Sakamoto Y 2013 Interrelationships between the innervations from the
Crit Rev Oral Biol Med 14:413–29. laryngeal nerves and the pharyngeal plexus to the inferior pharyngeal
Hollinshead WH 1982 Anatomy for Surgeons, vol I: The Head and Neck, constrictor. Surg Radiol Anat 35:721–8.
3rd ed. Philadelphia: Harper & Row. Sakamoto Y 2014 Gross anatomical observations of attachments of the
An older textbook that provides a valuable account of the anatomy of the middle pharyngeal constrictor. Clin Anat 27:603–9.
pharynx and of tissue spaces in the neck. It is also a thorough guide to the
Sato K, Nakashima T 2006 Human adult deglutition during sleep. Ann Otol
earlier literature.
Rhinol Laryngol 115:334–9.
Humbert IA, German RZ 2013 New directions for understanding neural Sato K, Nakashima T 2007 Sleeprelated deglutition in children. Ann Otol
control in swallowing: the potential and promise of motor learning. Rhinol Laryngol 116:747–53.
Dysphagia 28:1–10.
Steele CM, Miller AJ 2010 Sensory input pathways and mechanisms in swal
Ison S, Remmers JE, Tanaka A et al 1997 Anatomy of pharynx in patients lowing: a review. Dysphagia 25:323–33.
with obstructive sleep apnea and in normal subjects. J Appl Physiol
Thexton A 1998 Some aspects of swallowing. In: Harris M, Edgar M, Meghji
84:1319–26.
S (eds) Clinical Oral Science. Oxford: Wright; pp. 150–66.
Jafari S, Prince RA, Kim DY et al 2003 Sensory regulation of swallowing and


Thexton AJ, Crompton AW 1998 The control of swallowing. In: Linden RWA
airway protection: a role for the internal superior laryngeal nerve in
(ed) The Scientific Basis of Eating. Taste and Smell, Salivation, Mastica
humans. J Physiol 550:287–304.
tion and Swallowing and their Dysfunctions. Frontiers of Oral Biology
Johal AMA, Patel SI, Battagel JM 2007 The relationship between craniofacial Series, vol 9. Basel: Karger; pp. 168–222.
anatomy and obstructive sleep apnoea: a casecontrolled study. J Sleep
Wang C, Kundaria S, FernandezMiranda J et al 2014 A description of arterial
Res 16:319–26.
variants in the transoral approach to the parapharyngeal space. Clin
Kelly BN, Huckabee ML, Jones RD et al 2007 The first year of human life: Anat 27:1016–22.
coordinating respiration and nutritive swallowing. Dysphagia 22:
WoodJones I 1940 The nature of the soft palate. J Anat 77:147–70.
37–43.
Yuca K, Varsak YK 2012 Thornwaldt’s cyst. Eur J Gen Med 9:(Suppl 1)
Kendall KA, Leonard RJ, McKenzie SW 2001 Accommodation to changes in
26–9.
bolus viscosity in normal deglutition: a videofluoroscopic study. Ann
Otol Rhinol Laryngol 110:1059–65.


CHAPTER
35
Larynx
The larynx is an air passage, a sphincter and an organ of phonation, The thyroid, cricoid and the greater part of the arytenoid cartilages
and extends from the tongue to the trachea. It projects ventrally between consist of hyaline cartilage and may undergo mottled calcification as
the great vessels of the neck and is covered anteriorly by skin, fasciae age advances, starting about the twenty-fifth year in the thyroid cartilage
and the infrahyoid strap muscles that lower the hyoid bone and the and somewhat later in the cricoid and arytenoids. By the sixty-fifth year,
larynx. Above, it opens into the laryngopharynx and forms its anterior these cartilages commonly appear patchily dense in radiographs. The
wall; below, it continues into the trachea (see Fig. 34.2). It is mobile corniculate, cuneiform, tritiate and epiglottic cartilages and the apices
on deglutition. At rest, the larynx lies opposite the third to sixth cervical of the arytenoid are composed of elastic fibrocartilage, with little ten-
vertebrae in adult males; it is somewhat higher in children and adult dency to calcify (Munir Turk 1993).
females. In infants between 6 and 12 months, the tip of the epiglottis The surface anatomy of the laryngeal cartilages is described on
(the highest part of the larynx) lies a little above the junction of the page 413.
dens and body of the axis vertebra (Mijallili et al 2012). Until puberty,
male and female larynges are similar in size. After puberty, the male
larynx enlarges considerably in comparison with that of the female; all EPIGLOTTIS
the cartilages increase in both size and weight, the thyroid cartilage
projects in the anterior midline of the neck, and its sagittal diameter The epiglottis is a thin, leaf-like plate of elastic cartilage that projects
nearly doubles. The male thyroid cartilage continues to increase in size obliquely upwards behind the tongue and hyoid body, and in front of


until 40 years of age, after which no further growth occurs. For further the laryngeal inlet (see Figs 35.2–35.3, 35.5). Its free end, which is
reading, including an introduction to the more important historical broad and round, and occasionally notched in the midline, is directed
literature, see Berkovitz et al (2000), Blitzer et al (2009), Dickson and upwards. Its attached part, or stalk (petiolus), is long and narrow and
Maue-Dickson (1982), Kaplan (1971), Hollinshead (1982), Tucker is connected by the elastic thyroepiglottic ligament to the back of the
(1993). laryngeal prominence of the thyroid cartilage just below the thyroid
notch. Its sides are attached to the arytenoid cartilages by aryepiglottic
folds (which contain the aryepiglottic muscle). Its free upper anterior,
SKELETON OF THE LARYNX
or lingual, surface is covered by mucosa (the epithelium is non-
keratinized stratified squamous), which is reflected on to the pharyn-
The skeletal framework of the larynx is formed by a series of cartilages geal aspect of the tongue and the lateral pharyngeal walls as a median
interconnected by ligaments and fibrous membranes, and moved by a glossoepiglottic, and two lateral glossoepiglottic, folds. This arrange-
number of muscles (Figs 35.1–35.3). The hyoid bone is attached to the ment produces a depression, the vallecula, on each side of the median
larynx; it is usually regarded as a separate structure with distinctive and lateral folds. The lower part of its anterior surface, behind the hyoid
functional roles, and is described on page 443. The laryngeal cartilages bone and thyrohyoid membrane, is connected to the upper border of
are the midline, single thyroid, cricoid and epiglottic cartilages, and the the hyoid by an elastic hyoepiglottic ligament, and separated from the


paired arytenoid, cuneiform, corniculate and tritiate cartilages. thyrohyoid membrane by adipose tissue, which constitutes the clini-
cally important pre-epiglottic space. The smooth posterior, or laryngeal,
surface is transversely concave and vertically concavo-convex, and is
covered by ciliated respiratory mucosa; its lower projecting part is called
Hyoid bone, lesser
Hyoid bone, body cornu
Median Hyoid bone, greater Hyoid bone,
thyrohyoid cornu lesser cornu Epiglottis
ligament Lateral thyrohyoid Hyoid bone,
ligament greater cornu
Thyrohyoid
membrane Cartilago triticea Cartilago triticea
Thyroid notch Aperture for internal Thyrohyoid
laryngeal nerve and membrane Lateral thyrohyoid
Laryngeal superior laryngeal ligament
prominence artery
Thyroid cartilage, Thyroid cartilage,
Laminae of superior cornu superior cornu
thyroid cartilage
Superior thyroid Thyroepiglottic
Median tubercle ligament Thyroid lamina
cricothyroid Oblique line Articular capsule of Corniculate
ligament Inferior thyroid cricoarytenoid joint cartilage
tubercle
Anterior arch of Conus elasticus Thyroid cartilage, Arytenoid
cricoid inferior cornu cartilage
Posterior
Cricotracheal Thyroid cartilage, Cricoid lamina cricoarytenoid
ligament inferior cornu ligament
Articular capsule of Cricotracheal
First tracheal cricothyroid joint ligament A ofr t cic riu cl oa tr h c ya rop is du jl oe int
cartilage
First tracheal
cartilage
586 Fig. 35.1 An anterolateral view of the laryngeal cartilages and ligaments. Fig. 35.2 A posterior view of the laryngeal cartilages and ligaments.


Skeleton of the larynx
587
53
RETPAHC
A Thyroid cartilage
Superior cornu Attachment of Laryngeal prominence Superior cornu
Thyroid notch false vocal folds
Sternothyroid
Thyrohyoid
Laryngeal
prominence Superior thyroid
tubercle
Oblique line
Inferior tubercle Inferior cornu
Inferior cornu Attachment of Thyropharyngeus, part of
true vocal folds inferior constrictor
Anterior aspect Posterior aspect Lateral aspect
B Cricoid cartilage
For articulation
with arytenoid cartilage
Tendon of origin of
longitudinal fibres of
oesophagus Cricothyroid
For articulation For articulation
with thyroid cartilage with thyroid
cartilage
Posterior
Lateral
cricoarytenoid Cricopharyngeus,
cricoarytenoid
part of inferior constrictor
Superior aspect Posterior aspect Left lateral aspect
C Arytenoid cartilage: medial aspect D Epiglottis: posterior aspect
Epiglottic
Transverse cartilage
arytenoid
Vocal process For articulation
with cricoid cartilage
E Cricoarytenoid articulation
Fovea Corniculate cartilage Apex Corniculate
triangularis Vocal process cartilage
Arytenoid cartilage
Fovea Posterior cricoarytenoid Muscular
Muscular
oblonga ligament process
process
Vocal ligament
Vocal Vocal ligament Articulation with
process arytenoid cartilage
Stalk of
For articulation epiglottis
with thyroid cartilage
For articulation
with thyroid cartilage Cricoid cartilage
Arch of the cricoid cartilage
Lamina of the Median crest
cricoid cartilage
Superior aspect Posterior aspect Left lateral aspect
Fig. 35.3 Cartilages of the larynx: thyroid (A), cricoid (B), arytenoid (C), epiglottis (D), cricoarytenoid joint (E). The attachments of the false vocal
folds (vestibular ligaments; above) and the true vocal folds (vocal ligaments; below) are shown in A, posterior aspect. Note the pitted surface of the
epiglottis (D).
the tubercle. This surface forms the oblique anterior wall of the laryn- base of the tongue and active contraction of the aryepiglottic muscles.


geal vestibule. The cartilage is posteriorly pitted by small mucous glands Normally, the epiglottis diverts food and liquids away from the laryn-
(see Fig. 35.3D) and is perforated by branches of the internal laryngeal geal inlet and into the lateral food channels. It is not essential for res-
nerve and fibrous tissue, which means that the posterior surface of the piration or phonation.
epiglottis is in continuity through these perfora tions with the pre- Whether downward movement of the epiglottis is a passive process,
epiglottic space. produced by a combination of the weight of food or liquid on its
lingual surface and forces originating elsewhere in the hyoid and larynx,
or whether it is an active process brought about by active muscular
Functions of the epiglottis
control, remains the subject of debate. Neither scheme seems to explain
epiglottic movement satisfactorily. It is likely that a combination of
During swallowing, the hyoid bone moves upwards and forwards, and processes is taking place, in which passive forces originating in the
the epiglottis is bent posteriorly as a result of passive pressure from the tongue, hyoid and larynx are transmitted to the epiglottis by the


LARynx
588
4
nOITCES
hyo epiglottic ligaments while the base of the epiglottis is actively Cricoid lamina
moved by thyroarytenoid and muscles of the laryngeal inlet (Logemann
et al 1992, Vandaele et al 1994). Ardran and Kemp (1967) argue that,
The cricoid lamina is approximately quadrilateral in outline, and
though safe swallowing is possible without an epiglottis, more care has
2–3 cm in vertical dimension. It bears a posterior median vertical ridge
to be taken whilst eating.
that creates posterior concavities on either side. The two fasciculi of the
longitudinal layer of oesophageal muscle fibres (muscularis externa) are
attached by a tendon to the upper part of the ridge. Posterior cricoaryt-
THYROID CARTILAGE
enoid attaches to a shallow depression on either side of the ridge.
A discernible circular synovial facet, facing posterolaterally, some-
The thyroid cartilage is the largest of the laryngeal cartilages (see Figs times marks the junction of the lamina and arch; it indicates the site
35.1–35.3). It consists of two quadrilateral laminae with anterior where the cricoid articulates with the inferior thyroid cornu. The in-
borders that fuse along their inferior two-thirds at a median angle to ferior border of the cricoid is horizontal, and joined to the first tracheal
form the subcutaneous laryngeal prominence (‘Adam’s apple’). This cartilage by the cricotracheal ligament (see Fig. 35.1). The superior
projection is most distinct at its upper end, and is well marked in men border runs obliquely up and back, and gives attachment anteriorly to
but less visible in women. Above, the laminae are separated by a the thick median cricothyroid ligament, and laterally to the conus elas-
V-shaped superior thyroid notch or incisure. Posteriorly, the laminae ticus (see Fig. 35.1) and lateral cricoarytenoid. The posterosuperior
diverge, and their posterior borders are prolonged as slender horns: the aspect of the lamina presents a shallow median notch, on each side of


superior and inferior cornua. A shallow ridge, the oblique line, curves which is a smooth, oval, convex facet, directed upwards and laterally,
downwards and forwards on the external surface of each lamina; it runs for articulation with the base of an arytenoid cartilage.
from the superior thyroid tubercle, lying a little anterior to the root of The internal surface of the cricoid cartilage is smooth and lined by
the superior cornu, to the inferior thyroid tubercle on the inferior mucosa.
border of the lamina. Often, the oblique line is barely visible or is just
a faint line and only the tubercles are prominent. Sternothyroid, thyro- Subglottic stenosis
hyoid and thyropharyngeus (part of the inferior pharyngeal constrictor)
are attached to the oblique line, usually as little more than a tendon
Congenital malformation of the cricoid cartilage may result in severe
(see Fig. 35.3A).
narrowing of the subglottic airway and respiratory obstruction, which,
The internal surface of the lamina is smooth. Above and behind, it
in severe cases, is present from birth. It is the third most common
is slightly concave and covered by mucosa. The thyroepiglottic ligament,
congenital disorder of the larynx. The cause is unknown. Acquired
the paired vestibular and vocal ligaments, the thyroarytenoid, thyroepi-
subglottic stenosis is more common and is the result of trauma and
glottic and vocalis muscles, and the stalk of the epiglottis are all attached
scarring following prolonged endotracheal intubation for the purposes
to the inner surface of the cartilage, in the angle between the laminae.
of ventilation of premature babies (Walner et al 2009).
The true vocal folds lie 6–9 mm below the median thyroid notch. The
superior border of each lamina is concave posteriorly and convex anter-
iorly, dropping sharply to form the thyroid notch; the thyrohyoid mem- ARYTENOID CARTILAGE
brane is attached along the superior border (see Figs 35.1, 35.2). The
inferior border of each lamina is concave posteriorly and nearly straight


The paired arytenoid cartilages articulate with the lateral parts of the
anteriorly; the two parts are separated by the inferior thyroid tubercle.
superior border of the cricoid lamina (see Figs 35.2–35.3C, E). Each is
Anteriorly, the thyroid cartilage is connected to the cricoid cartilage by
pyramidal and has three surfaces, two processes, a base and an apex.
the median (anterior) cricothyroid ligament, which is the thickened
The posterior surface, which is triangular, smooth and concave, is
medial portion of the conus elasticus.
covered by transverse arytenoid. The anterolateral surface is convex and
The anterior border of each thyroid lamina fuses with its partner at
rough, and bears, near the apex of the cartilage, an elevation from which
an angle of approximately 90° in men and approximately 120° in
a crest curves back, down and then forwards to the vocal process. The
women. The shallower angle in men is associated with the larger laryn-
lower part of this arcuate crest separates two depressions (foveae). The
geal prominence, the greater length of the vocal cords, and the resultant
upper is triangular (fovea triangularis), and the vestibular ligament is
deeper pitch of the voice. The posterior border is thick and rounded,
attached to it. The lower is oblong (fovea oblonga), and vocalis and
and receives fibres of stylopharyngeus and palatopharyngeus. The su-
lateral cricoarytenoid are attached to it. The medial surface is narrow,
perior cornu, which is long and narrow, curves upwards, backwards and
smooth and flat, and is covered by mucosa; its lower edge forms the
medially, and ends in a conical apex to which the lateral thyrohyoid
lateral boundary of the intercartilaginous part of the rima glottidis. The
ligament is attached. The inferior cornu is short and thick, and curves
base is concave, with a smooth surface for articulation with the lateral
down and slightly anteromedially. On the anteromedial surface of its
part of the upper border of the cricoid lamina. Its round, prominent


lower end there is a small oval facet for articulation with the side of the
lateral angle, or muscular process, projects backwards and laterally; it
cricoid cartilage; this facet is variable and is only sometimes well
gives attachment to posterior cricoarytenoid behind and lateral crico-
defined.
arytenoid in front. The vocal ligament is attached to its pointed anterior
During infancy, some older authors describe a narrow, rhomboidal,
angle (vocal process), which projects horizontally forwards. The apex
flexible strip, the intrathyroid cartilage, lying between the two thyroid
curves backwards and medially, and articulates with the corniculate
laminae and joined to them by fibrous tissue. The significance of this
cartilage.
structure is not clear.
CORNICULATE CARTILAGES
CRICOID CARTILAGE
The corniculate cartilages are two conical nodules of elastic cartilage
The cricoid cartilage is attached below to the trachea, and articulates that articulate with the apices of the arytenoid cartilages, prolonging
with the thyroid cartilage and the two arytenoid cartilages by synovial them posteromedially (see Figs 35.3E, 35.8). They lie in the posterior
joints. It forms a complete ring around the airway, the only laryngeal parts of the aryepiglottic mucosal folds, and are sometimes fused with
cartilage to do so (see Fig. 35.3B). It is smaller, but thicker and stronger, the arytenoid cartilages.
than the thyroid cartilage, and has a narrow curved anterior arch and a
broad, flatter posterior lamina.
CUNEIFORM CARTILAGES
Cricoid arch
The cuneiform cartilages are two small, elongated, club-like nodules of
elastic cartilage, one in each aryepiglottic fold anterosuperior to the
The cricoid arch is vertically narrow in front (5–7 mm in height) and corniculate cartilages, and are visible as whitish elevations through the
widens posteriorly towards the lamina. Cricothyroid is attached to the mucosa (see Fig. 35.8).
external aspect of its front and sides, and cricopharyngeus (part of


the inferior pharyngeal constrictor) is attached behind cricothyroid. The
arch is palpable below the laryngeal prominence, from which it is sepa- TRITIATE CARTILAGES (CARTILAGO TRITICEA)
rated by a depression containing the conus elasticus. The inferior border
of the cartilage is nearly horizontal and is circular in outline, whereas The tritiate cartilages are two small nodules of elastic cartilage, situated
the upper border is more elliptical. one on either side above the larynx within the posterior free edge of


Soft tissues
589
53
RETPAHC
the thyrohyoid membrane, about halfway between the superior cornu cartilage and the bases of the arytenoids (see Figs 35.2, 35.3E, 35.4).
of the thyroid cartilage and the tip of the greater cornu of the hyoid Each joint is enclosed by a capsular ligament and strengthened by a
bone (see Figs 35.1–35.2). Their functions are unknown, although they ligament that, although traditionally called the posterior cricoarytenoid
may serve to strengthen this connection. ligament, is largely medial in position.
Other inconstant or supernumerary cartilages may occur in the The cricoid facets are elliptical, convex and obliquely directed
larynx. They are the small, paired sesamoid cartilages, found at the laterally, anteriorly and downwards. The long axes of the two facets
lateral edges of the arytenoid cartilages, and a single interarytenoid intersect posteriorly at an angle of about 50°. Two movements occur at
cartilage, enclosed by the cricopharyngeal ligament. this joint. The first is rotation of the arytenoid cartilages at right angles
to the long axis of the cricoid facet (dorso-medio-cranial to ventro-
latero-caudal), which, because of its obliquity, causes each vocal process
CALCIFICATION OF LARYNGEAL CARTILAGES
to swing laterally or medially, thereby increasing or decreasing the
width of the rima glottidis. This movement is sometimes referred to as
The thyroid, cricoid and most of the arytenoid cartilages consist of a rocking movement of the arytenoid cartilages. There is also a gliding
hyaline cartilage and may therefore become calcified. This process nor- movement, by which the arytenoids approach or recede from one
mally starts at about 18 years of age. Initially, it involves the lower and another, the direction and slope of their articular surfaces imposing a
posterior part of the thyroid cartilage, and subsequently spreads to forward and downward movement on lateral gliding. The movements
involve the remaining cartilages, calcification of the arytenoid cartilage of gliding and rotation are associated, i.e. medial gliding occurs with


starting at its base. The degree and frequency of calcification of the medial rotation and lateral gliding with lateral rotation, resulting in
thyroid and cricoid cartilages appear to be less in females. There is some adduction or abduction of the vocal folds, respectively. When viewed
evidence to suggest that a predilection for tumour invasion may be from above, foreshortening can give the illusion that the arytenoid
enhanced by calcification of the laryngeal cartilages (Hatley et al 1965). cartilages are rotating about their vertical axes, but the shape of the
The tip and upper portion of the vocal process of the arytenoid facets prevents such movement occurring (Selbie et al 1998). However,
cartilage consists of non-calcifying, elastic cartilage. This may have con- some authors maintain that rotatory movement about a vertical axis
siderable functional significance: the vocal process may bend at the can occur (Liu et al 2013). The posterior cricoarytenoid ligaments limit
elastic cartilage during adduction and abduction, and the two arytenoid forward movements of the arytenoid cartilages on the cricoid cartilage.
cartilages will contact mainly at their ‘elastic’ superior portions during It has been suggested that the ‘rest’ position of the cricoarytenoid liga-
adduction. ment is a major determinant of the position of a denervated vocal cord
(England et al 1996).
JOINTS
ARYTENOCORNICULATE JOINTS
CRICOTHYROID JOINT
Synovial or cartilaginous joints link the arytenoid and corniculate
The joints between the inferior cornua of the thyroid cartilage and the cartilages.
sides of the cricoid cartilage are synovial. Each is enveloped by a cap-
sular ligament strengthened posteriorly by fibrous bands (see Figs
35.1–35.2; Fig. 35.4). Both capsule and ligaments are rich in elastin INNERVATION OF THE CRICOTHYROID,
fibres. The primary movement at the joint is rotation around a trans- CRICOARYTENOID AND
verse axis that passes transversely through both cricothyroid joints.
ARYTENOCORNICULATE JOINTS
There is some controversy as to whether the cricoid or thyroid cartilage


rotates more. The effect of this rotation is to move the cricoid and
The cricothyroid, cricoarytenoid and arytenocorniculate joints are
thyroid cartilages relative to one another in such a way as to bring
innervated by branches of the recurrent laryngeal nerves, which arise
together or approximate the lamina of the thyroid cartilage and the arch
either independently or from branches of the nerve to the laryngeal
of the cricoid cartilage (‘closing the visor’). When the joint is in a neutral
muscles. The capsules of the laryngeal joints contain numerous lamel-
position, the ligaments are slack and the cricoid can glide, to a limited
lated (Pacinian) corpuscles, Ruffini corpuscles and free nerve endings
extent, in horizontal and vertical directions on the thyroid cornua. The
(Bradley 2000).
effect of these movements is to lengthen the vocal folds, provided the
arytenoid cartilages are stabilized at the cricoarytenoid joint. This may
also increase vocal fold tension. For further reading, see Vilkman et al
SOFT TISSUES
(1987), Hammer et al (2010).
The skeletal framework of the larynx is joined to surrounding structures
CRICOARYTENOID JOINT by extrinsic membranes. It is also interconnected by intrinsic ligaments
and fibroelastic membranes, of which the thyrohyoid and quadrangu-
The cricoarytenoid joints are a pair of synovial joints between the facets lar membranes, together with the conus elasticus, are the most signifi-
on the lateral parts of the upper border of the lamina of the cricoid cant. The thyrohyoid membrane is external to the larynx, whereas the
A B
Superior cornu
30º Muscular process Arytenoid cartilage
Thyroid cartilage
Oblique line
Cricoarytenoid
joint
Arch of
cricoid
cartilage
Inferior cornu
15º
Lamina of Lamina of
cricoid cartilage cricoid cartilage
Cricothyroid joint Arch of Vocal process
cricoid cartilage
Fig. 35.4 A, A lateral view of the cricothyroid joint. B, An anterosuperior view of the cricoarytenoid joint.


Larynx
589.e1
53
RETPAHC
There is a significant amount of variation in the shape of the crico-
thyroid facet, which can vary in shape from a well-defined facet to a
nearly flat surface with just a slight protuberance or, in some cases, to
no obvious definable facet. The shape of the facet determines the degree
of horizontal and vertical gliding possible at the joint, and thus the
degree of elongation of the vocal folds in each case, which has been
shown to vary between 3% and 12%. It has been suggested that this
variation might be one factor in determining the success of cricothyroid
approximation surgery aimed at raising the pitch of the voice in male
to female transsexuals (Chen et al (2012), Hammer et al (2010), Wind-
isch et al (2010), Storck et al (2011)).


LARynx
590
4
nOITCES
paired quadrangular membranes and conus elasticus are internal. The A
named ligaments are the median (anterior) cricothyroid ligament, the
Hyoepiglottic ligament
hyoepiglottic and thyroepiglottic ligaments, and the cricotracheal
Airway
ligament.
Hyoid bone
EXTRINSIC LIGAMENTS AND MEMBRANES
Thyrohyoid membrane Quadrangular membrane
(left)
Rima glottidis between
The thyrohyoid membrane is a broad, fibroelastic layer attached below the vocal ligaments
Thyroid lamina Cuneiform cartilage
to the superior border of the thyroid cartilage lamina and the front of
its superior cornua, and above to the superior margin of the body and Thyroepiglottic ligament Corniculate cartilage
Cut surface of
greater cornua of the hyoid (see Figs 35.1–35.2; Fig. 35.5C). It thus
thyroid cartilage
ascends behind the concave posterior surface of the hyoid, separated Arytenoid cartilage
from its body by a bursa that facilitates the ascent of the larynx during Left vocal ligament
Vocal process of
swallowing. Its medial portion is thickened, forming the median thyro- arytenoid cartilage
hyoid ligament. The more lateral, thinner, parts are pierced by the Conus elasticus
superior laryngeal vessels and internal laryngeal nerves (see Fig. 35.1).
Externally, it is in contact with thyrohyoid and omohyoid, and with the
Left vestibular ligament,
body of the hyoid bone. Its inner surface is related to the lingual surface middle portion removed
of the epiglottis and the piriform fossae of the pharynx. The round,
cord-like, elastic lateral thyrohyoid ligaments form the posterior borders
of the thyrohyoid membrane, and connect the tips of the superior
thyroid cornua to the posterior ends of the greater hyoid cornua. For B
further reading, see Bosma and Bartner (1993). Tongue
Hyo- and thyroepiglottic ligaments
Epiglottis
Hyoepiglottic ligament
Vallecula


The epiglottis is attached to the hyoid bone and thyroid cartilage by
the extrinsic hyoepiglottic and intrinsic thyroepiglottic ligaments, Laryngeal vestibule Hyoid bone
respectively (see Fig. 35.5A).
Aryepiglottic fold Pre-epiglottic fat body
Cricotracheal ligament Cuneiform cartilage
Thyrohyoid membrane
Corniculate cartilage
The cricotracheal ligament unites the lower border of the cricoid to the Vestibular fold
first tracheal cartilage, and is thus continuous with the perichondrium Interarytenoid muscle
of the trachea (see Fig. 35.1). Ventricle of larynx
Arytenoid cartilage
Thyroid cartilage
INTRINSIC LIGAMENTS AND MEMBRANES Vocal process of
Vocal fold
arytenoid cartilage
The fibroelastic membrane of the larynx lies within the cartilaginous Lamina of cricoid Arch of cricoid cartilage
skeleton of the larynx, beneath the laryngeal mucosa (see Fig. 35.5). It cartilage
forms a discontinuous sheet, separated on both sides of the larynx by Cartilages of trachea
a horizontal cleft between the vestibular and vocal ligaments. Its upper
part, the quadrangular membrane, lies within the walls of the upper Infraglottic cavity
part of the laryngeal cavity, the laryngeal vestibule, and extends between C
the arytenoid cartilages and the sides of the epiglottis. Its lower part, Hyoid bone,
the conus elasticus, lies within the walls of the lower part of the laryn- greater cornu
geal cavity, the infraglottic cavity, and connects the thyroid, cricoid and Thyrohyoid
arytenoid cartilages. membrane
Cut surface of
Opening for hyoid bone
Quadrangular membrane neurovascular
bundle Epiglottis
Each quadrangular membrane passes from the lateral margin of the
Thyroepiglottic ligament
epiglottis to the apex and fovea triangularis of the ipsilateral arytenoid Quadrangular
cartilage. It is often poorly defined, especially in its upper portion. The membrane


upper and lower borders of the membrane are free. The upper border Cut surface of
slopes posteriorly to form the aryepiglottic ligament, which constitutes Corniculate cartilage thyroid cartilage
the central component of the aryepiglottic fold. Posteriorly, it passes
Muscular process Vestibular ligament
through the fascial plane of the oesophageal suspensory ligament, and of arytenoid
helps to form the median corniculopharyngeal ligament, which extends cartilage
into the submucosa adjacent to the cricoid cartilage. This ligament may Vocal ligament
exert vertical traction on the tissues of the laryngopharynx. The cunei- Vocal process of
Conus elasticus
form cartilages lie within the aryepiglottic folds. The lower border of arytenoid cartilage
the quadrangular membrane forms the vestibular ligament within the
vestibular fold. Cricotracheal Cricoid cartilage
ligament
Cricothyroid membrane and conus elasticus
The conus elasticus is that part of the fibroelastic membrane found in
the lower part of the cavity of the larynx. The terminology used to Fig. 35.5 A and B, Sagittal sections of the left side of the larynx, showing
describe this structure is confusing, as different terms may be used the laryngeal membranes (A) and the interior aspect (B) of the left half
to describe apparently similar structures. Two synonyms for the of the larynx. C, The quadrangular membrane viewed from the left side.
conus elasticus that are commonly found in the literature are the crico- (A, With permission from Drake RL, Vogl AW, Mitchell A (eds), Gray’s
vocal membrane and the cricothyroid membrane. The conus elasticus Anatomy for Students, 2nd ed, Elsevier, Churchill Livingstone. Copyright
2010.)


Laryngeal cavity
591
53
RETPAHC
consists of three distinct parts: right and left lateral parts and a thick- sound production. The supraglottis is a clinical term sometimes used
ened median portion. The term conus elasticus is frequently applied to in tumour staging; it refers to all those parts of the larynx that lie above
the lateral parts, while the median part is often called either the median the glottis and thus comprises the laryngeal inlet (formed of the laryn-
or the anterior cricothyroid ligament. geal surface of the epiglottis and arytenoid cartilages, and the laryngeal
aspects of the aryepiglottic folds), the laryngeal vestibule and the ves-
Median (anterior) cricothyroid ligament The median or anterior tibular folds. Other terms that are used clinically in tumour staging are
cricothyroid ligament is the thickened central portion of the conus the glottis, defined as the anterior and inferior surfaces of the true vocal
elasticus. Inferiorly, it is attached to the upper border of the midline folds and the anterior and posterior commissures; and the subglottis,
region of the cricoid arch and it extends upwards to attach to the inferior defined as the region below the glottis that extends to the inferior
border of the thyroid cartilage, passing on to the inner surface of the border of the cricoid cartilage.
thyroid angle as far superiorly as the attachment of thyroarytenoid.
Conus elasticus The lateral parts of the conus elasticus are thinner MICROSTRUCTURE OF THE LARYNX
than the median cricothyroid ligament. Inferiorly, the conus elasticus
attaches to the superior cricoid arch and the cricoid lamina. Superiorly,
The laryngeal mucosa is continuous with that of the pharynx above and
it does not attach to the inferior border of the thyroid cartilage but
the trachea below. It lines the entire inner surface of the larynx, includ-
extends upwards within the thyroid lamina to attach anteriorly to the
ing the ventricle and saccule, and is thickened over the vestibular folds,
inner surface of the thyroid cartilage (just below its midpoint) and


where it is the chief component. Over the vocal folds, it is thinner and
posteriorly to the tip, upper surface and fovea oblonga of the arytenoid
is firmly attached to the underlying vocal ligaments. It is loosely adher-
cartilage. Between these anterior and posterior attachments, the upper
ent to the anterior surface of the epiglottis but firmly attached to its
edges of the conus elasticus are free, thickened and aligned horizontally,
anterior surface and the floor of the valleculae. On the aryepiglottic
forming the vocal ligaments. Each vocal ligament lies within a mucosa-
folds, it is reinforced by a considerable amount of fibrous connective
covered vocal fold, covered on its internal surface by the mucosal lining
tissue, and it adheres closely to the laryngeal surfaces of the cuneiform
of the larynx, and externally by the lateral cricoarytenoid and thyroaryt-
and arytenoid cartilages.
enoid muscles (Reidenbach 1995).
The laryngeal epithelium is mainly a ciliated, pseudostratified respir-
The conus elasticus derives its name from the cone or funnel shape
atory epithelium (see Fig. 2.2D) where it covers the inner aspects of the
produced by the superior and medial curving of its walls between its
larynx, including the lower part of the posterior, laryngeal surface of the
inferior and superior attachments that is thought to maximize the effi-
epiglottis, and it provides a mucociliary clearance mechanism shared
cient flow of air towards the rima glottidis during phonation (Len-
with most of the respiratory tract. The vocal folds, however, are covered
neberg 1967).
by non-keratinized, stratified squamous epithelium where they contact
each other; this important variation protects the tissue from the effects
LARYNGEAL CAVITY of the considerable mechanical stresses that act on the surfaces of the
vocal folds. The exterior surfaces of the larynx, which merge with the
laryngopharynx and oropharynx (including the anterior, lingual and
The laryngeal cavity extends from the laryngeal inlet opening into the


upper, posterior surfaces of the epiglottis and the upper parts of the
pharynx down to the lower border of the cricoid cartilage, where it
aryepiglottic folds), are subject to the abrasive effects of swallowed food,
continues into the trachea (see Fig. 35.5; Fig. 35.6). The walls of the
and are therefore also covered by non-keratinized, stratified squamous
cavity are formed of the fibroelastic membranes described above and
epithelium.
lined with mucous membrane that folds over the free edges of these
The laryngeal mucosa has numerous mucous glands, especially over
membranes within the larynx. On either side, the continuity of the
the epiglottis, where they pit the cartilage, and along the margins of the
fibroelastic membrane is interrupted between the upper vestibular and
aryepiglottic folds anterior to the arytenoid cartilages, where they are
lower true vocal folds.
known as the arytenoid glands. Many large glands in the saccules of the
The folds project into the lumen of the cavity and divide it into
larynx secrete periodically over the vocal folds during phonation. The
upper and lower parts, separated by a middle portion between the two
free edges of these folds are devoid of glands, and their stratified epi-
sets of folds that leads into the laryngeal ventricle. The upper folds are
thelium is vulnerable to drying and requires the secretions of neigh-
the vestibular (ventricular or false vocal) folds; the median aperture
bouring glands; hoarseness as a result of excessive speaking is due to
between them is the rima vestibuli. The lower pair are the (true) vocal
partial temporary failure of this secretion. The epithelial surfaces are
folds (or vocal cords), and the fissure between them is the rima glottidis
ridged and this may help retain the lubricating secretions over the sur-
or glottis. The true vocal folds are the primary source of phonation,
faces of the edges of the folds. Poorly lubricated folds offer increased
whereas the vestibular folds normally do not contribute directly to
resistance to airflow, which means that higher subglottal pressures are
needed to initiate phonation. Taste buds, like those in the tongue, are


present on the posterior epiglottic surface and aryepiglottic folds, and
less often in other laryngeal regions. Laryngeal stretch-, touch- and
Epiglottis pressure-sensitive mechanoreceptors provide perceptual and proprio-
ceptive afferent information for a variety of essential functions, includ-
ing airway protection, breathing, deglutition, speech and voice (Hammer
Hyoid bone, and Krueger 2014).
Aryepiglottic greater cornu
Laryngeal
fold
vestibule;
supraglottic Thyrohyoid UPPER PART
membrane
cavity
Tubercle of
Quadrangular
epiglottis The upper part of the laryngeal cavity consists of the laryngeal inlet
membrane
(aditus), the aryepiglottic fold and the laryngeal vestibule.
Saccule of larynx
Laryngeal Vestibular fold
ventricle Thyroid cartilage Laryngeal inlet (aditus)
Laryngeal ventricle The upper part of the laryngeal cavity is entered by the laryngeal inlet
(aditus laryngis), an approximately triangular aperture between the
Vocal fold larynx and pharynx. This faces backwards and somewhat upwards
Infraglottic
cavity Thyroarytenoid because the anterior wall of the larynx is much longer than the posterior
Conus (and slopes downwards and forwards in its upper part because of the
elasticus; Cricoid cartilage oblique inclination of the epiglottis). The inlet is bounded anteriorly
cricovocal
by the upper edge of the epiglottis, posteriorly by the transverse mucosal
membrane
fold between the two arytenoids (posterior commissure), and on each
Rima glottidis side by the edge of a mucosal ridge, the aryepiglottic fold, that runs
between the side of the epiglottis and the apex of the arytenoid cartilage.
Fig. 35.6 A coronal section through the larynx and the cranial end of the The midline groove between the two corniculate tubercles is termed the
trachea, posterior aspect. interarytenoid notch.


LARynx
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4
nOITCES
Aryepiglottic fold Vocal folds (cords) and ligaments
The aryepiglottic fold contains ligamentous and muscular fibres. The The vocal folds are concerned with sound production. The free thick-
ligamentous fibres represent the free upper border of the quadrangular ened upper edge of the conus elasticus forms the vocal ligament (see
membrane (see Fig. 35.5). The muscle fibres are continuations of the (Fig. 35.5C). It stretches back on either side from the midlevel of the
oblique arytenoids. The posterior part of the aryepiglottic fold contains thyroid angle to the vocal processes of the arytenoids. When covered by
two oval swellings, one above and in front, the other behind and below, mucosa, it is termed the vocal fold or vocal cord (cord is the preferred
that mark the positions of the underlying cuneiform and corniculate clinical term) (see Figs 35.5B–35.6). The vocal folds lie on either side
cartilages, respectively. They are separated by a shallow vertical furrow of a fissure, the rima glottidis, and form the anterolateral three-fifths of
that is continuous below with the opening of the laryngeal ventricle. its edges. The posterior two-fifths of the edges of the rima glottidis are
formed by the vocal processes of the arytenoid cartilages (to which the
Laryngeal vestibule vocal folds are attached).
Each vocal fold consists of five layers, namely: mucosal epithelium,
lamina propria (three layers) and a muscular layer (fibres of thyroaryt-
The laryngeal vestibule is the region between the laryngeal inlet and
vestibular folds. It is wide above, narrow below, and higher anteriorly
enoid and vocalis) (Fig. 35.7). The mucosa overlying the vocal ligament
is thin and attached to the underlying lamina propria by a basement
than posteriorly. The anterior wall is formed by the posterior surface
membrane. It lies directly on the ligament, and so the vocal fold appears
of the epiglottis, the lower part of which (epiglottic tubercle) bulges


pearly white in vivo. At birth, the lamina propria consists of a single
backwards a little. The lateral walls, higher in front and shallow
layer of cells. It becomes a bilaminar structure by 2 months of age and
behind, are formed by the medial surfaces of the aryepiglottic folds.
three layers become established by 7 years of age (Hartnick 2005). The
The posterior wall consists of the interarytenoid mucosa above the
lamina propria is composed of three layers. The most superficial con-
ventricular folds.
sists of loose collagen and elastic fibres and is only loosely attached to
the underlying vocal ligament, an arrangement that produces a poten-
MIDDLE PART tial space (Reinke’s space) that extends along the length of the free
margin of the vocal ligament and a little way on to the superior surface
of the cord; oedema fluid readily collects here in disease. The intermedi-
The middle part of the laryngeal cavity is the smallest, and extends
ate layer consists of elastic fibres, and the deep layer is formed of col-
from the rima vestibuli above to the rima glottidis below. On each side
lagen fibres; these two layers collectively form the vocal ligament. The
it contains the vestibular folds, the ventricle and the saccule of the
appearance of differential fibres – namely, elastin and collagen – is
larynx.
noted at 13 years of age (Hartnick 2005). Fibres of thyroarytenoid and
Vestibular folds and ligaments vocalis form the fifth layer of the vocal folds; they shorten, relax and
aid adduction of the vocal folds (see p. 596).
The site where the vocal folds meet anteriorly, the anterior commis-
The narrow vestibular ligament represents the thickened lower border
sure, is the region where fibres of the vocal ligament pass through the
of the quadrangular membrane (see Fig. 35.5C). It is fixed in front to
thyroid cartilage to blend with the overlying perichondrium. The point
the thyroid angle below the epiglottic cartilage and behind to the ante-
at which the vocal ligaments attach to the thyroid cartilage is known as
rolateral surface of the arytenoid cartilage above its vocal process. With
Broyles ligament; it contains blood vessels and lymphatics, and there-


its covering of mucosa, it is termed the vestibular (ventricular or false
fore represents a potential route for the escape of malignant tumours
vocal) fold (see Figs 35.5B–35.6). The presence of a loose vascular
from the larynx. This is a very significant anatomical escape pathway
mucosa lends the vestibular folds a pink appearance in vivo, as they lie
for primary tumours arising on the vocal cord.
above and lateral to the vocal cords. Muscle fibres can be observed
Located at the anterior and posterior end of each vocal ligament are
within the vestibular folds, though they are variable in extent between
the maculae flavae. These form conspicuous mucosal bulges visible on
individuals. Their function is disputed, with some authors suggesting
endoscopic examination of the larynx through the mucosa as whitish
that, when present, they produce an adductive (or medializing) and
yellow masses. The vocal folds are connected to thyroid cartilage an-
downward movement on the vestibular folds (Reidenbach 1991, Moon
teriorly via the anterior maculae flavae and the anterior commissure
and Alipour 2013).
tendon, and posteriorly via the posterior maculae flavae. The maculae
flavae themselves are described as being formed of dense masses of
Ventricle of the larynx
stellate cells with a morphology markedly different from that of fibro-
blasts surrounded by a dense extracellular matrix. The function of the
The laryngeal ventricle (also known as the laryngeal sinus) is a slit maculae flavae remains unclear but it has been suggested that they play
between the vestibular folds above and the true vocal folds below (see a critical role in the growth, development and metabolism of the extra-
Figs 35.5–35.6). On each side, it extends from a narrow opening in the cellular matrix of the vocal folds (Awd Allah et al 2009, Fayoux et al
wall of the middle part of the laryngeal cavity into a fusiform recess 2004, Sato et al 2010a, 2010b).
that extends upwards into the laryngeal wall, lateral to the vestibular
fold, and opens anteriorly into the saccule. Laryngeal carcinoma


Squamous cell carcinoma is by far the most common laryngeal neo-
Saccule of the larynx plasm. The pattern of spread is largely determined by anatomical fea-
tures at the site of origin and this, in turn, influences its management
The saccule is a pouch of variable size that ascends forwards from the and potential outcomes (Welsh et al 1989, Kirchner and Carter 1987).
anterior end of the ventricle, between the vestibular fold and thyroid Reinke’s oedema
cartilage (see Fig. 35.6), and occasionally reaches the upper border of
The mucous membrane is loosely attached throughout the larynx. It
the cartilage or even beyond, when it protrudes through the thyrohyoid
can accommodate considerable swelling, which may compromise the
membrane. It is conical and curves slightly backwards; between 60 and
airway in acute infections. At the edge of the true vocal folds, the
70 mucous glands, sited in the submucosa, open on to its luminal
mucosal covering is tightly bound to the underlying ligament so that
surface. The orifice of the saccule is guarded by a delicate fold of
oedema fluid does not pass between the upper and lower compartments
mucosa, the ventriculosaccular fold.
of the vocal cord mucosa. Any tissue swelling above the vocal cord
The saccule has a fibrous capsule that is continuous below with the
exaggerates the potential space deep to the mucosa (Reinke’s space),
vestibular ligament. It is covered medially by a few muscular fasciculi
causing accumulation of extracellular fluid and flabby swelling of the
from the apex of the arytenoid cartilage that pass forwards between the
vocal cords (Reinke’s oedema). The oedema can persist because there
saccule and vestibular mucosa into the aryepiglottic fold; laterally, it is
is very poor lymphatic drainage from the edges of the vocal folds (Liu
separated from the thyroid cartilage by the thyroepiglottic muscle. The
et al 2006). Vocal abuse may initiate such changes, but the condition
latter compresses the saccule, expressing its secretion on to the vocal
is nearly always confined to smokers.


cords, which lack glands, to lubricate and protect them against desic-
cation and infection. Vocal cord nodules
Laryngoceles and saccular cysts Vocal fold nodules are chronic lesions of the vocal folds and develop
most commonly as the result of persistent overuse of the voice, which
has caused an increase in vocal fold tension and a more forceful adduc-
Available with the Gray’s Anatomy e-book tion. They normally develop at the point of maximum contact of the


Larynx
592.e1
53
RETPAHC
Laryngoceles and saccular cysts are air- or fluid-filled enlargements of
the saccule. A laryngocele is a herniation of the saccular mucosa. The
aetiology is uncertain; repeated, sustained, high transglottal pressures
(such as in trumpet playing) may be a possible cause of acquired symp-
toms, and some cases may be the result of congenital enlargement of
the saccule. Growth of a laryngocele is constrained by the surrounding
tissues, and so it expands upwards into the paraglottic space anterior to
the piriform fossa, and superiorly to expand the aryepiglottic fold and
reach the vallecula (internal laryngocele). It can extend to the thyro-
hyoid membrane, which it may pierce to form an external laryngocele,
and where it may be palpable in the neck. Symptoms include hoarse-
ness, stridor and dysphagia. The laryngeal saccule may also become
pathologically enlarged as a result of obstruction of the ventricular
aditus by inflammation, scarring, or compression by a tumour; an
expanding, mucus-filled cyst forms as the glandular secretions accumu-
late. These fluid-filled saccular cysts can expand in a similar direction
to a laryngocele and may also pierce the thyrohyoid membrane. In
addition to hoarseness and stridor, acute respiratory obstruction may
occur, especially in the young, if the contents of the cyst become
infected.
There are alternative descriptions of the soft tissues of the vocal folds.
Some authors describe only two layers, namely: the body (the deep layer
of the lamina propria and the muscle) and the cover (the mucosa and
superficial and intermediate layers of the lamina propria). Others divide
the soft tissues of the vocal folds into three layers: the mucosal layer
(the mucosa and the superficial layer of the lamina propria), the vocal
ligament (the intermediate and deep layers of the lamina propria) and
the muscle layer (Titze 1994).
Supraglottic tumours arising from the laryngeal surface of the epi-
glottis have a tendency to spread through the perforations in the epi-


glottic cartilage and into the pre-epiglottic space, through which
branches of the internal laryngeal nerve pass. It is likely that the neural
deficit this may cause accounts for the most common presenting
symptom: a feeling of something in the throat and discomfort when
swallowing. In some, this space becomes filled with tumour and can
even infiltrate the hyoid bone. Inferior spread into the paraglottic space
is more common and may extend as far as the subglottis or even beyond
the larynx. Spread in this space medializes the vocal cord; this can be
seen on careful laryngoscopy when assessing the tumour stage and may
be confirmed by scans. Lateral spread into the piriform sinus is also a
feature of tumours arising lower down in the supraglottis on the ves-
tibular folds. Deeper invasion infiltrates the thyroarytenoid muscle and
eventually the thyroid and arytenoid cartilages.
Ventricular tumours often obstruct mucus outflow from the saccule
to cause a saccular cyst or mucocele. Further infiltration of the paraglot-
tic space and transglottic spread ultimately fixes the vocal cord through
muscle invasion and, more rarely, direct involvement of the cricoaryt-
enoid joint or infiltration of the recurrent laryngeal nerve. Fixation of
the vocal cord is a good indicator of a tumour within the paraglottic
space and this is reflected in the TNM staging system as an adverse sign.
Glottic tumours tend to spread by local growth in the first instance,
when they may be contained in Reinke’s space for some time. The
paucity of lymphatics in the vocal cord slows tumour progression,
allowing time for the patient to present to a clinician with a relatively
small tumour load that will only have caused a chronic husky voice.
This anatomical feature also accounts for the relative lack of nodal
metastases associated with small glottic tumours. The proximity of
anterior cord tumours to the thyroid cartilages, separated only by a thin
layer of connective tissue, predisposes to cartilage invasion; spread of
tumour via Broyles ligament to the outside of the larynx changes the
tumour stage from a T1 lesion to a T4 lesion, with both therapeutic and


survival implications. More posterior cord tumours tend to invade the
vocalis muscle and fix it.
Subglottic tumours usually spread circumferentially and, by doing
so, impair the airway.


Laryngeal cavity
593
53
RETPAHC
A
Non-keratinized squamous epithelium B
Pseudostratified ciliated columnar Mucosa
respiratory epithelium
Superficial Layers of
Intermediate lamina
Vestibular fold
Deep propria
Vocal fold
C
Thyroarytenoid and vocalis
Mucosa
Superficial Layers of
Intermediate lamina
Deep propria
Thyroarytenoid and vocalis
Fig. 35.7 A, A coronal view of the laryngeal cavity, showing the distribution of the mucous membrane in the laryngeal cavity. B, The structure of the true
vocal folds at low power, × 40, stained with Movat’s pentachrome stain. C, The true vocal folds at high power, × 100; Movat’s pentachrome stain. The
non-keratinized squamous epithelium is shown forming a mucosal layer over the superficial part of the lamina propria, along with the three layers of the
lamina propria, with thyroarytenoid and vocalis lying deep to the deep layer of the lamina propria. At higher magnification, the deeper yellow staining of
the collagen in the deep layer of the lamina propria compared to the superficial layer indicates a greater degree of cross-linking. (B,C, Modified with
permission from Courey MS, The Professional Voice, In: Cummings CW et al (eds) Otolaryngology: Head and Neck Surgery, vol 4, 3rd edn. St Louis:
Mosby: 3003–25.)
Interarytenoid area Trachea the level of the vocal cords. The glottis is customarily divided into two
regions: an anterior intermembranous part, which makes up about
three-fifths of its anteroposterior length and is formed by the underlying
vocal ligament; and a posterior intercartilaginous part, formed by the
Corniculate vocal processes of the arytenoid cartilages. It is the narrowest part of the
tubercle
larynx, having an average sagittal diameter in adult males of 23 mm,
Cuneiform and in adult females of 17 mm; its width and shape vary with the


tubercle Piriform sinus movements of the vocal cords and arytenoid cartilages during respira-
Aryepiglottic tion and phonation.
fold
True vocal fold
Vestibular (false) LOWER PART
vocal fold
Rima The lower part of the laryngeal cavity, the infraglottic cavity (also known
glottidis Epiglottis as the subglottic cavity), extends from the vocal cords to the lower
border of the cricoid. In transverse section, it is elliptical above and
Vallecula wider and circular below, and is continuous with the trachea. Its walls
Base of tongue are lined by respiratory mucosa, and are supported by the cricothyroid
ligament above and the cricoid cartilage below (Reidenbach 1998). The
Fig. 35.8 The true vocal folds viewed through a fibreoptic endoscope.
walls of this part of the laryngeal cavity are said to be exponentially
(With permission from Berkovitz BKB, Moxham BJ 2002. Head and Neck
Anatomy. London: Martin Dunitz.) curved, a feature that may serve to accelerate the airflow towards the
glottis with the minimum loss of energy (Lenneberg 1967).
vocal folds, i.e. at the junction of the anterior third and the posterior LARYNGOSCOPIC EXAMINATION
two-thirds of the vocal ligament. Excessive trauma at this point, e.g.
when singing with poor technique or forcing the voice, initially pro-
The laryngeal inlet, the structures around it, and the cavity of the larynx
duces subepithelial haemorrhage or bruising; in time, this results in
can all be inspected using fibreoptic endoscopy, through either the
pathological changes such as subepithelial scarring (‘singer’s nodes’ or
mouth or nasopharynx. The epiglottis is seen foreshortened but its
‘clergyman’s nodes’). Nodules increase vocal fold mass and affect vocal
tubercle is visible. From the epiglottic margins, the aryepiglottic folds
fold closure; the persistent posterior glottal opening causes hoarseness,
can be traced posteromedially and the cuneiform and corniculate eleva-


a breathy voice, reduced vocal intensity and an inability to produce
tions recognized. The pink vestibular folds and pearly white vocal cords
higher frequencies of vibration. These changes can cause a cycle in
are visible, and, when the rima glottidis is wide open, the anterior arch
which increasing vocal effort is required by way of compensation, and
of the cricoid cartilage, the tracheal mucosa and cartilages may be seen
this exacerbates the problem (Aronson and Bless 2009).
(see Fig. 35.8). The piriform fossae can also be inspected.
Rima glottidis
LARYNGEAL OBSTRUCTION AND TRAUMA
The rima glottidis or glottis is the fissure between the vocal cords anter-
iorly and the arytenoid cartilages posteriorly (Fig. 35.8). It is bounded The mucosa of the upper larynx is highly sensitive and contact with
behind by the mucosa that passes between the arytenoid cartilages at foreign bodies excites immediate coughing. Large foreign bodies may


LARynx
594
4
nOITCES
obstruct the laryngeal inlet or rima glottidis and suffocation may terior sagittal communication between the larynx and pharynx. For
ensue. Smaller articles may enter the trachea or bronchi, or lodge in the further reading, see Adewale (2009), Hudgins et al (1997), Pracy (1983)
laryngeal ventricle and cause reflex closure of the glottis with subse- and Sapienza et al (2004).
quent suffocation. Inflammation of the upper larynx, e.g. secondary to
infection or the effects of smoke inhalation, may swell the mucosa by
PARALUMENAL SPACES
effusion of fluid into the loose submucous tissue (oedema of the supra-
glottis). The effusion neither involves nor extends below the vocal cords
because the mucosa here is bound directly to the vocal ligaments and A number of potential spaces lie between the laryngeal cartilages and
there is no submucous tissue. Laryngotomy below the vocal cords the ligaments and membranes that support them. The three main
through the cricothyroid ligament, or tracheotomy below the cricoid spaces are the pre-epiglottic, the paraglottic and the subglottic spaces.
cartilage, may be necessary to restore a free airway. Their precise definition, and the extent to which they communicate
The consequences of trauma to the larynx resulting from either blunt with one another, remain controversial. They are not closed compart-
or penetrating injuries may lead to any or all of the following: oedema, ments and so their existence does not preclude the spread of tumours.
haematoma, fracture, dislocations or paralysis. Trauma at the level of An awareness of the anatomy of these spaces, and the potential path-
the rima glottidis may result in thyroid cartilage fracture and displace- ways of tumour spread from them, have significantly influenced the
ment of the fragments into the vocal folds posteriorly with consequent surgical approach to disease in this region (Welsh et al 1983).
oedema. Suicidal wounds are usually made through the thyrohyoid
membrane, damaging the epiglottis, superior thyroid vessels, external


and internal carotid arteries, and internal jugular veins. Less frequently, PRE-EPIGLOTTIC SPACE
these wounds are inflicted above the hyoid, so that the lingual muscles
and lingual and facial vessels are damaged. Caustic substances swal- Its name implies that the pre-epiglottic space (Fig. 35.9) lies anterior
lowed accidentally or during a suicide attempt, the ingestion of hot to the epiglottis. The upper part of this space also extends beyond the
liquids and the inspiration of hot gases may all result in serious laryn- lateral margins of the epiglottis, an arrangement that gives the space the
geal damage. Radiotherapy as part of the treatment for neck cancer can form of a horseshoe and has led to the suggestion that periepiglottic
cause radiation burns within the larynx (Myer 2004). space would be a more appropriate term for this region (Reidenbach
1996a). The space is primarily filled with adipose tissue and does not
appear to contain any lymph nodes.
THE PAEDIATRIC LARYNX
The upper boundary is formed by the weak hyoepiglottic membrane,
strengthened medially as the median hyoepiglottic ligament; the anter-
The paediatric larynx differs markedly from its adult counterpart in size, ior boundary is the thyrohyoid membrane, strengthened medially as
position, consistency and shape. Although it is about one-third adult the median thyrohyoid ligament; and the lower boundary is the thyro-
size, it is proportionately larger; the lumen is short and funnel-shaped, epiglottic ligament, continuous laterally with the quadrangular mem-
and disproportionately narrower. The infant larynx lies higher in the brane behind. The greater cornu of the hyoid bone forms its upper
neck than the adult larynx (see Fig. 34.11). At rest, the upper border of lateral border. Inferolaterally, the pre-epiglottic space is in continuity
the infant epiglottis is at the level of the second or third cervical verte- with the paraglottic space, from where it is often invaded by the laryn-


bra; when the larynx is elevated, it reaches the level of the first cervical geal saccule. It is also in continuity with the mucosa of the laryngeal
vertebra. This high position enables an infant to use its nasal airway to surface of the epiglottis via multiple perforations in the cartilage of the
breathe while suckling. It also means that the larynx is protected some- epiglottis (Reidenbach 1996a).
what by the jaw. The epiglottis is X-shaped, with a furled petiole, and
the laryngeal cartilages are softer and more pliable than in the adult
larynx (which may predispose to airway collapse in inspiration, leading PARAGLOTTIC SPACE
to the clinical picture of laryngomalacia). The thyroid cartilage is shorter
and broader, and lies closer to the hyoid bone in the neonate, which The paraglottic space (see Fig. 35.9) is a region of adipose tissue that
means that the thyrohyoid ligament is relatively short. Neither the contains the internal laryngeal nerve, the laryngeal ventricle, and all or
superior notch nor the laryngeal prominence is as marked as it is in the part of the laryngeal saccule. It is bounded laterally by the thyroid car-
adult. The cricoid cartilage is the same shape as in the adult. Calcifica- tilage and thyrohyoid membrane, superomedially by the quadrangular
tion of the cricoid cartilage has been noted as early as 7 years of age membrane, inferomedially by the conus elasticus, and posteriorly by
(Strauss 2000). The arytenoid cartilages are larger in proportion to the the piriform fossa. The lower border of the thyroid cartilage is inferior,
larynx as a whole and so are more prominent; the aryepiglottic folds and the paraglottic space is continuous inferiorly with the space between
are disproportionally large. The vocal cords are 4–4.5 mm long, which the cricoid and thyroid cartilages. Anteroinferiorly, there are deficiencies
is relatively shorter than either in childhood or in the adult, and con- in the paramedian gap at the side of the median cricothyroid ligament,


sequently the proportion of the rima glottidis that is intramembranous and posteroinferiorly, adipose tissue extends towards the cricothyroid
is smaller in the neonate. The ventricle of the larynx is small, whereas joint. Superiorly, the paraglottic space is usually continuous with the
the saccule of the larynx is often considerably larger than it is in adult pre-epiglottic space, although the two spaces may be separated by a
life. The time at which the infant larynx assumes adult characteristics fibrous septum. There is disagreement between authors as to the precise
varies in the literature from 5 to 12 years; some adults retain a funnel- boundaries between these two spaces. Some authorities exclude thyro-
shaped larynx (Wheeler et al 2009). Further discussion is beyond the arytenoid from the paraglottic space and include it within the pre-
scope of this book; the interested reader should consult Wheeler et al epiglottic space, forming its inferior border posterolaterally (Reidenbach
(2009) and Holzki et al (2010). 1996b).
The mucosa of the vestibule is more loosely attached than it is in
the adult larynx and it exhibits multiple submucosal glands. Inflamma-
SUBGLOTTIC SPACE
tion of the vestibule will therefore rapidly result in gross oedema. The
mucosa is also lax in the infraglottic cavity and swelling here rapidly
causes severe respiratory obstruction because of the disproportionally The subglottic space is bounded laterally by the conus elasticus, medi-
narrower lumen (3.5 mm in diameter in neonates). The neonatal inf- ally by the mucosa of the infraglottic cavity, and above by the under-
raglottic cavity extends posteriorly as well as inferiorly, which is an surface of Broyles ligament in the midline. It is continuous below with
important consideration when passing an endotracheal tube (Litman the inner surface of the cricoid cartilage and its mucosa (Reidenbach
et al 2003). The infraglottic airway rapidly increases in size during the 1998).
first two years of life (Eckel et al 1999). By about the third year, sexual


differences become apparent: the larynx is larger in boys, although the
MUSCLES
angle between the thyroid laminae is more pronounced in girls. At
puberty, these changes increase and there is greater enlargement of the
male larynx. The muscles of the larynx may be divided into extrinsic and intrinsic
Congenital anomalies of the larynx include aplasia and hypoplasia groups. The extrinsic muscles connect the larynx to neighbouring struc-
of the epiglottis, high-rising epiglottis, bifid epiglottis, saccular cysts, tures and are responsible for moving it vertically during phonation and
vocal cord palsy, laryngeal atresia, laryngocele, laryngo-tracheo- swallowing. They include the infrahyoid strap muscles, thyrohyoid,
oesophageal cleft and laryngeal web. Laryngo-tracheo-oesophageal cleft sternothyroid and sternohyoid, and the inferior constrictor muscle of
is due to failure of fusion of the posterior cricoid lamina and abnormal the pharynx. Two of the three elevator muscles of the pharynx, stylo-
development of the tracheo-oesophageal septum, resulting in a pos- pharyngeus and palatopharyngeus, are also connected directly to the


Larynx
594.e1
53
RETPAHC
Paraglottic space Pre-epiglottic space Hyoid bone Aryepiglottic fold
Internal Internal C4 spinous Piriform
jugular vein carotid artery process fossa
Fig. 35.9 A contrast-enhanced axial computed tomogram of the neck of
a 42-year-old male showing the paraglottic and pre-epiglottic spaces.
(Courtesy of Dr Ivan Zammit.)


Muscles
595
53
RETPAHC
thyroid cartilage, mainly to the posterior aspect of the thyroid laminae Actions The oblique arytenoids and aryepiglottic muscles act as a
and cornua. sphincter of the laryngeal inlet by adducting the aryepiglottic folds and
The role of the extrinsic muscles during respiration appears to be approximating the arytenoid cartilages to the tubercle of the epiglottis.
variable; the larynx has been seen to rise, descend or barely move during Their poor development limits their capacity to act as a sphincter of the
inspiration. The extrinsic muscles can affect the pitch and the quality inlet. The oblique interarytenoids are weak adductors of the vocal folds,
of the voice by raising or lowering the larynx, and geniohyoid elevates and may be more effective in this action than the transverse interaryt-
and anteriorly displaces the larynx, particularly during deglutition. enoids because of the superior mechanical advantage.
Elevation of the larynx decreases the length and calibre of the laryn-
Transverse (inter)arytenoid
gopharynx and thus shortens the vocal tract overall. This tends to raise
both the formant frequencies as well as the fundamental frequency and Transverse arytenoid is a single, unpaired muscle deep to the oblique
may be one way by which an increase in pitch is achieved, though a interarytenoids (see Fig. 35.10C). It bridges the gap at the back of the
change in pitch is not an inevitable consequence of this movement. The larynx between the two arytenoid cartilages and fills their concave pos-
raising of the larynx may also be accompanied by forward or backward terior surfaces. It is attached to the back of the muscular process and
movement of the tongue because of the attachment of the tongue to adjacent lateral border of both arytenoids.
the hyoid bone. These movements may facilitate alveolar or velar articu-
lations, respectively. Vascular supply Transverse arytenoid receives its blood supply from
The larynx is lowered by contraction of the infrahyoid muscles. This the laryngeal branches of the superior and inferior thyroid arteries.
increases the length of the laryngopharynx, tending to lower both the


formant frequencies and the fundamental frequency, though, again, a Innervation Transverse arytenoid is innervated by the recurrent laryn-
pitch change is not inevitable. Another effect of lowering the larynx will geal nerves. It also receives branches from the internal laryngeal nerve,
be to decrease supraglottal pressure and this will facilitate the articula- although there is debate as to whether these branches contain any
tion of voiced stops and fricatives (to a lesser extent). Voice quality can distinct motor input. The nerves form a dense, but highly variable,
also be varied by the height of the larynx and this is an important factor plexus.
contributing to the variations in quality of voice between different
speakers. Actions Transverse arytenoid pulls the arytenoid cartilages towards
The intrinsic muscles are the cricothyroid, posterior and lateral crico- each other, closing the posterior, intercartilaginous, part of the rima
arytenoid, transverse and oblique arytenoid, aryepiglotticus, thyro- glottidis (termed adductive tensing by phoneticians) (see Fig. 35.10C).
arytenoid and its subsidiary part, vocalis, and thyroepiglotticus; all are During a whisper, the muscle is relaxed while lateral cricoarytenoid
confined to the larynx in their attachments, and all but the transverse contracts, allowing air to escape during phonation. This action is
arytenoid are paired (Fig. 35.10). Whereas most of the intrinsic muscles accomplished by drawing the arytenoids upwards to slide along the
lie internally, under cover of the thyroid cartilage or the mucosa, the sloping shoulders of the cricoid lamina, without rotation.
cricothyroids appear on the outer aspect of the larynx.
Posterior cricoarytenoid
The intrinsic laryngeal muscles may be placed in three groups
according to their main actions. The posterior and lateral cricoaryten- Posterior cricoarytenoid arises from the posterior surface of the cricoid
oids and oblique and transverse arytenoids vary the degree of abduction lamina (see Fig. 35.10A). Its fibres ascend laterally and converge to
and adduction of the vocal folds and thus the dimensions and the insert on the upper and posterior surfaces of the muscular process of


degree of opening of the rima glottidis. The cricothyroids, posterior the ipsilateral arytenoid cartilage. The highest fibres run almost hori-
cricoarytenoids, thyroarytenoids and vocalis regulate the length and zontally, the middle run obliquely, and the lowest are almost vertical;
tension of the vocal folds. In reality, the obliquity of the cricoarytenoid some reach the anterolateral surface of the arytenoid cartilage. An addi-
facets means that some overlap in function between these two muscle tional strip of muscle, ceratocricoid, is occasionally seen in relation to
groups is inevitable. Thus, alterations in the dimensions of the rima the lower border of posterior cricoarytenoid, arising from the cricoid
glottidis will produce small changes in vocal fold length, and shorten- cartilage and inserting on to the posterior aspect of the inferior cornu
ing the vocal folds will also result in a degree of adduction. The third of the thyroid cartilage.
group of muscles is the oblique arytenoids, aryepiglottic and thyroepi-
glottic muscles, which modify the laryngeal inlet. Bilateral pairs of Vascular supply Posterior cricoarytenoid receives its blood supply
muscles usually act in concert with each other. from the laryngeal branches of the superior and inferior thyroid
Neuromuscular spindles have been found in all human laryngeal arteries.
muscles, the maximum number being found in the transverse arytenoid
(Blitzer et al 2009). The control of phonation requires very considerable Innervation Posterior cricoarytenoid is innervated by the recurrent
neuromuscular coordination, and effective proprioception would laryngeal branch of the vagus.
appear to be essential to this capacity. The mass of muscle related to
adduction far outweighs that related to abduction. In this context, it is Actions The posterior cricoarytenoids are the only laryngeal muscles
of interest to note that histological examination of normal larynges that open the glottis. They rotate the arytenoid cartilages laterally
revealed evidence of some degenerative changes in posterior cricoary- around an axis that passes through the long axis of the facets of the


tenoid, the single muscle associated with abduction, but none in the cricoarytenoid joints, producing separation of the vocal processes and
remaining muscles (Guindi et al 1981). the attached vocal cords (see Fig. 35.10A). They also pull the arytenoids
backwards, assisting the cricothyroids to lengthen the vocal cords. The
Anatomical variations in the anatomy of the laryngeal most lateral fibres draw the arytenoid cartilages laterally, and so the
muscles rima glottidis becomes triangular when the posterior cricoarytenoid
muscles contract. The posterior cricoarytenoids are active in the produc-
Available with the Gray’s Anatomy e-book tion of unvoiced sounds.
Lateral cricoarytenoid
INTRINSIC MUSCLES
Lateral cricoarytenoid is attached anteriorly to the upper border of the
cricoid arch. It ascends obliquely backwards to be attached to the front
Oblique arytenoid and aryepiglotticus of the muscular process of the ipsilateral arytenoid cartilage (see Fig.
The oblique arytenoids lie superficial to the transverse arytenoid 35.10B).
and are sometimes considered to be part of it. They cross each other
obliquely at the back of the larynx, each extending from the back of the Vascular supply Lateral cricoarytenoid receives its blood supply
muscular process of one arytenoid cartilage to the apex of the opposite from the laryngeal branches of the superior and inferior thyroid
one (see Fig. 35.10D). Some fibres continue laterally round the aryten- arteries.
oid apex into the aryepiglottic fold, forming the aryepiglottic muscle
(aryepiglotticus). Innervation Lateral cricoarytenoid is innervated by 1–6 branches of
the anterior terminal division of the recurrent laryngeal nerve, with the
Vascular supply Oblique arytenoid receives its blood supply from most frequent pattern consisting of 3 branches. In the majority of cases,
the laryngeal branches of the superior and inferior thyroid arteries. these branches arise over the muscle itself.
Innervation Oblique arytenoid is innervated by the recurrent laryn- Actions Lateral cricoarytenoid rotates the arytenoid cartilage in a


geal nerve. direction opposite to that of posterior cricoarytenoid, and so closes the


Larynx
595.e1
53
RETPAHC
Numerous variations in the anatomy of the intrinsic muscles have been
described in the literature. The more frequently found ones are described
in the main text. A particularly comprehensive source documenting
these variations was published in 1875 by Fürbringer. Later authors
have studied many of these variations but estimates of their frequency
often vary significantly between the various studies; the functional sig-
nificance of many of these variations is not clear.


LARynx
596
4
nOITCES
A B
Rima glottidis Thyroid cartilage
Arch of
the cricoid
cartilage
Vocal
ligament
Vocal
process
Arytenoid
cartilage
Muscular
process
Lamina of the
cricoid cartilage
Posterior Lateral cricoarytenoid
cricoarytenoid
Posterior aspect Superior aspect Lateral aspect
C D
Transverse interarytenoid Oblique interarytenoid
Posterior aspect Posterior aspect Arytenoid cartilage
E Vocal ligament F
Thyroid cartilage
Vocalis muscle
Thyroarytenoid
Superior aspect
Cricoid cartilage
Oblique part
Cricothyroid
Straight part
Lateral aspect
Fig. 35.10 The intrinsic muscles of the larynx in posterior or lateral views, with their actions shown alongside in a superior view. The arrows indicate the
direction of movement of the cartilage in each case.


Vascular supply and lymphatic drainage
597
53
RETPAHC
rima glottidis (see Fig. 35.10B). As it does so, it brings the tips of the External carotid artery Superior laryngeal artery
vocal processes together, closing the ligamentous part of the rima glot-
tidis, an action known as medial compression. The action of lateral Left vagus nerve
cricoarytenoid in adducting the vocal folds is therefore distinct and
complementary to that of the oblique and transverse arytenoid muscles. Internal carotid Superior laryngeal nerve
artery
Contraction of lateral cricoarytenoid also results in shortening and
relaxing of the vocal folds. Right vagus nerve Internal laryngeal nerve
Thyrohyoid membrane
External laryngeal nerve
Cricothyroid
Cricothyroid is attached anteriorly to the external aspect of the arch of
Superior thyroid artery
the cricoid cartilage (see Fig. 35.10F). Its fibres pass backwards and
diverge into two groups: a lower ‘oblique’ part, which slants backwards
Position of vocal folds
and laterally to the anterior border of the inferior cornu of the thyroid;
Cricothyroid
and a superior ‘straight’ part, which ascends more steeply backwards to Median cricothyroid
the posterior part of the lower border of the thyroid lamina. The medial ligament
borders of the paired cricothyroids are separated anteriorly by a trian- Right recurrent Left vagus nerve
gular gap occupied by the median cricothyroid ligament. laryngeal nerve Left recurrent
Inferior thyroid artery laryngeal nerve
Vascular supply Cricothyroid is supplied by the cricothyroid Trachea
Right subclavian
artery, a branch of the superior thyroid artery, which crosses high
artery Thyrocervical trunk
on the cricothyroid ligament to communicate with its contralateral
fellow.
Innervation Unlike the other intrinsic muscles of the larynx, cricothy- Left subclavian artery
roid is innervated by the external branch of the superior laryngeal nerve,
and not by the recurrent laryngeal nerve.
Actions Cricothyroid lengthens and affects the tension in the vocal Manubrium sterni


folds. It does this by shortening the space between the inferior border Ligamentum arteriosum
of the thyroid cartilage and the cricoid cartilage, an action that increases
Aortic arch
the distance between the tip of the vocal process of the arytenoid car-
tilage and the posterior surface of the lamina of the thyroid cartilage. Left pulmonary artery
Right pulmonary
Rotation occurs at the cricothyroid joint (see above). At the same time,
artery
the posterior part of cricothyroid pulls the thyroid cartilage forwards, a
gliding action that also lengthens the vocal folds. Some authors con-
sider that cricothyroid has a slight adductive action in moving the vocal
folds to a more paramedian position as they are lengthened and thinned
(Mu and Sanders 2009, Wadie et al 2013). Others have attributed the Oesophagus
relative sparing of abduction in lesions of the recurrent laryngeal nerve
Pulmonary trunk
to a weak abductive action of cricothyroid. These contradictory views
are currently unresolved.
Fig. 35.11 An anterior view of the blood supply and innervation of the
Thyroarytenoid and vocalis larynx. (With permission from Drake RL, Vogl AW, Mitchell A (eds), Gray’s
Thyroarytenoid is a broad, thin muscle, lying lateral to the vocal fold, Anatomy for Students, 2nd ed, Elsevier, Churchill Livingstone. Copyright
conus elasticus, laryngeal ventricle and saccule (see Fig. 35.10E). It is 2010.)
attached anteriorly to the lower half of the angle of the thyroid carti-
lage, and to the cricothyroid ligament. Its fibres pass backwards, later-
ally and upwards to the anterolateral surface of the arytenoid cartilage.
of the vocal ligaments by the vocalis muscles, combined with tension
The lower and deeper fibres form a band that, in coronal section,
in the anterior parts of the ligaments, is responsible for raising the pitch
appears as a triangular bundle attached to the lateral surface of the
of the voice. Vocalis can change the timbre of the voice by affecting the
vocal process and to the fovea oblonga on the anterolateral surface of
mass of the vocal cords.


the arytenoid cartilage. This bundle, the vocalis muscle, is viewed by
some authors as simply a deeper part of the thyroarytenoid and by Thyroepiglotticus
others as a distinct and separate muscle. The vocalis is parallel with,
Many of the fibres of thyroarytenoid are prolonged into the aryepiglot-
and just lateral to, the vocal ligament. It is said to be thicker behind
tic fold, where some terminate, and others continue to the epiglottic
than in front, because many deeper fibres start from the vocal ligament
margin as thyroepiglotticus. The thyroepiglotticus muscles can widen
and do not extend to the thyroid cartilage. (An alternative view is that
the inlet of the larynx by their action on the aryepiglottic folds.
all its fibres loop and intertwine as they pass from the thyroid to the
arytenoid cartilage.) A few fibres extend along the wall of the ventricle
from the lateral margin of the arytenoid cartilage to the side of the VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
epiglottis. Superior thyroarytenoid, an inconstant small muscle, lies on
the lateral surface of the main mass of thyroarytenoid; when present, it
The blood supply of the larynx is derived mainly from the superior and
extends obliquely from the thyroid angle to the muscular process of
inferior laryngeal arteries (Fig. 35.11). Rich anastomoses exist between
the arytenoid cartilage.
the corresponding contralateral laryngeal arteries and between the ipsi-
Vascular supply Thyroarytenoid receives its arterial blood supply lateral laryngeal arteries. The superior laryngeal arteries supply the
greater part of the tissues of the larynx, from the epiglottis down to the
from the laryngeal branches of the superior and inferior thyroid
level of the vocal cords, including the majority of the laryngeal muscu-
arteries.
lature. The inferior laryngeal artery supplies the region around cricothy-
Innervation All parts of thyroarytenoid are supplied by the recurrent roid, while its posterior laryngeal branch supplies the tissue around
posterior cricoarytenoid (Trotoux et al 1986).


laryngeal nerve. It also receives a communicating branch from the exter-
nal laryngeal nerve, although it is not clear whether such branches carry
motor or sensory fibres.
ARTERIES AND VEINS
Actions The thyroarytenoids draw the arytenoid cartilages towards the
Superior laryngeal artery
thyroid cartilage, thereby shortening and relaxing the vocal ligaments.
At the same time, they rotate the arytenoids medially in opposition to
the action of posterior cricoarytenoid to approximate the vocal folds The superior laryngeal artery is normally derived from the superior
and so aid closure of the rima glottidis. Relaxation of the posterior parts thyroid artery, a branch of the external carotid artery, as this artery


LARynx
598
4
nOITCES
passes down towards the upper pole of the thyroid gland (see Fig. Epiglottis Hyoid bone
29.14). Sometimes, however, it arises directly from the external carotid Lamina of thyroid cartilage Hyoid bone,
tip of greater cornu
artery between the origins of the superior thyroid and lingual arteries
or, less commonly, from the common carotid artery or carotid bifurca-
tion (Vazquez et al 2009). The superior laryngeal artery runs down
towards the larynx, with the internal branch of the superior laryngeal
nerve lying above it. It enters the larynx by penetrating the thyrohyoid
membrane and divides into a number of branches that supply the
Internal laryngeal
larynx from the tip of the epiglottis down to the inferior margin of nerve, ascending
thyroarytenoid. It anastomoses with its contralateral fellow and with division
the inferior laryngeal branch of the inferior thyroid artery.
Cricothyroid artery
The cricothyroid artery arises from the superior thyroid artery and may
Internal laryngeal
contribute to the supply of the larynx. It follows a variable course, either nerve, descending
superficial or deep to sternothyroid. If superficial, it may be accompa- division
nied by branches of the ansa cervicalis, and if deep, it may be related Oblique interarytenoid
to the external laryngeal nerve. It can anastomose with the artery of the
opposite side and with the laryngeal arteries.
Transverse interarytenoid
Inferior laryngeal artery
The inferior laryngeal artery is smaller than the superior laryngeal
Posterior cricoarytenoid
artery. It is a branch of the inferior thyroid artery, which arises from
the thyro cervical trunk of the subclavian artery (see Fig. 29.17). It
ascends on the trachea with the recurrent laryngeal nerve, enters the
larynx at the lower border of the inferior constrictor, just behind the
Thyroid gland
cricothyroid articulation, and supplies the laryngeal muscles and


mucosa. The inferior laryngeal artery anastomoses with its contralat-
eral fellow and with the superior laryngeal branch of the superior
thyroid artery.
A posterior laryngeal artery of variable size has been described as a
Inferior thyroid artery
regular feature that arises as an internal branch of the inferior thyroid
artery.
Superior and inferior laryngeal veins
Recurrent laryngeal nerve
Venous return from the larynx occurs via superior and inferior laryn- Trachea
geal veins, which run parallel to the laryngeal arteries and are tribu- Fig. 35.12 A posterior view of the laryngeal innervation.
taries of the superior and inferior thyroid veins, respectively. The
superior thyroid vein drains into the internal jugular vein, and the
inferior thyroid vein usually drains into the left brachiocephalic
vein.
INNERVATION
LYMPHATIC DRAINAGE
The larynx is innervated by the internal and external branches of the
superior laryngeal nerve, the recurrent laryngeal nerve and sympathetic
The vocal folds, with their firmly bound mucosa and paucity of lym- nerves (see Fig. 35.11; Fig. 35.12). Conventionally, the internal laryn-
phatics at their edges, provide a clear demarcation between the upper geal nerve is described as sensory, the external laryngeal nerve as motor,
and lower areas of the larynx. Above the vocal folds, the rich network and the recurrent laryngeal nerve as mixed. The internal laryngeal nerve
of lymph vessels draining the supraglottic part of the larynx accompany is sensory down to the vocal cords, the recurrent laryngeal nerve is
the superior laryngeal artery, pierce the thyrohyoid membrane, and end sensory below the vocal cords, and there is overlap between the terri-
in the upper deep cervical lymph nodes, often bilaterally. The supraglot- tories innervated by the two nerves at the vocal cords themselves. All
tic lymphatics also communicate with those at the base of the tongue. the intrinsic muscles of the larynx are supplied by the recurrent laryn-


Below the vocal fold, some of the lymph vessels of the infraglottic cavity geal nerve except for cricothyroid, which is supplied by the external
pass through the conus elasticus to reach the prelaryngeal (Delphian) laryngeal nerve. A number of anastomoses between the internal, exter-
and/or pretracheal and paratracheal lymph nodes, while others accom- nal and recurrent laryngeal nerves have been described, with varying
pany the inferior laryngeal artery and join the lower deep cervical nodes estimates of their incidence. Chronologically, the oldest recorded is that
(Welsh et al 1983, Werner et al 2003). between the recurrent laryngeal nerve and the internal laryngeal branch
of the superior laryngeal nerve (Galen’s anastomosis). The majority of
Nodal spread of laryngeal tumours these anastomoses are found on the posterior surface of the larynx,
forming what has been described as a laryngeal plexus to parallel the
pharyngeal plexus. Their precise nature and function are unclear, but
The upper deep cervical lymph nodes act as pathways for the spread of
since some are thought to convey motor fibres, it is reasonable to
malignant tumours of the supraglottic larynx. Up to 40% of these
assume that functions commonly ascribed to the three laryngeal nerves
tumours will have undergone such spread at the time of clinical pres-
may be more complex than the conventional descriptions imply, which
entation. As stated previously, the glottis is very poorly endowed with
may have potential clinical implications (Furlan et al 2002, Sato and
lymphatic vessels; some 95% of malignant tumours confined to the
Shimada 1995, Sanders et al 1993, Naidu et al 2014).
glottis will present only with a change in voice or airway obstruction,
The detailed course of the vagus in the neck is described on
but will not show signs of spread to adjacent lymph nodes at presenta-
page 466.
tion. Tumours of the subglottic larynx will often spread to the paratra-
cheal lymph node chain prior to clinical presentation. The presenting
Superior laryngeal nerve


symptoms are usually voice change and airway obstruction rather than
a mass in the neck. The paratracheal lymph nodes occupy a deep-seated
position in the root of the neck and so their enlargement may remain The superior laryngeal nerve arises from the middle of the inferior vagal
occult. They must be looked for carefully at surgery and included in any ganglion. It receives one or more communications from the superior
radiation field. cervical sympathetic ganglion; most frequently, the connection is with


Innervation
599
53
RETPAHC
the external laryngeal nerve. The sympathetic communication contrib- on the cricoid lamina and thyroarytenoid that form connections with
utes to the innervation of the carotid body (Monfared et al 2002) and the internal laryngeal nerve (Furlan et al 2002, Sanudo et al 1999).
the thyroid gland (Sun and Chang 1991). Though the superior laryngeal The recurrent laryngeal nerve does not always lie in a protected posi-
nerve usually lies on the medial side of the internal carotid artery, it tion in the tracheo-oesophageal groove but may be slightly anterior to
may be found on the lateral side of the artery. The superior laryngeal it (more often on the right), and it may be markedly lateral to the
nerve divides into two branches: a smaller, external and a larger, internal trachea at the level of the lower part of the thyroid gland. The upper
branch, approximately 1.5 cm below the ganglion. Rarely, both branches part of the nerve has a close but variable relationship to the inferior
may arise from the ganglion. thyroid artery. On the right, it is as often anterior to, or posterior to, or
intermingled with, the terminal branches of the artery. On the left, the
Internal laryngeal nerve nerve is usually posterior to the artery, though occasionally it lies an-
The internal laryngeal nerve passes forwards approximately 7 mm terior to it. The stated incidences of these relationships vary between
before piercing the thyrohyoid membrane, usually at a higher level than different authors. The recurrent laryngeal nerve may supply extralaryn-
the superior thyroid artery (Durham and Harrison 1962). It splits into geal branches to the larynx that arise before it passes behind the inferior
superior, middle and inferior branches on entering the larynx. The thyroid cornu (Bowden 1955).
superior branch supplies the mucosa of the piriform fossa. The large External to its capsule, the thyroid gland is covered by the visceral
middle branch is distributed to the mucosa of the ventricle, specifically layer of deep cervical fascia which splits into two layers at the posterior


the quadrangular membrane, and therefore probably conveys the affer- border of the gland. The anterior layer covers the entire medial surface
ent component of the cough reflex. The inferior ramus is mainly dis- of each lobe. At, or just above, the isthmus, this layer is conspicuously
tributed to the mucosa of the ventricle and subglottic cavity. On the thickened to form the lateral ligament of the thyroid gland, which
medial wall of the piriform fossa, descending branches give twigs to the attaches the gland to the trachea and the lower part of the cricoid car-
interarytenoid muscle and share a number of communicating branches tilage. The posterior layer passes behind the oesophagus and pharynx,
with the recurrent laryngeal nerve (Sanders and Mu 1998). and is attached to the prevertebral fascia. A compartment is thus
formed on each side of the midline, lateral to the trachea and oesopha-
External laryngeal nerve gus; it contains fat, the recurrent laryngeal nerve and terminal parts of
The external laryngeal nerve continues downwards and forwards on the the inferior thyroid artery. The nerve may be lateral or medial to the
lateral surface of the inferior constrictor, to which it contributes some lateral ligament of the thyroid gland, and sometimes may be embed-
small branches. Indeed, the nerve is sometimes located within the ded in it.
fibres of the constrictor muscle. It passes beneath the attachment of A very rare anomaly that is of relevance to laryngeal pathology and
sternothyroid to the oblique line of the thyroid cartilage and supplies surgery is the so-called ‘non-recurrent’ laryngeal nerve, where the right
cricothyroid. A communicating nerve continues from the posterior recurrent laryngeal nerve arises directly from the vagus nerve trunk high
surface of cricothyroid, crosses the piriform fossa and enters thyroaryt- up in the neck and enters the larynx close to the inferior pole of the
enoid, where it anastomoses with branches from the recurrent laryn- thyroid gland. Only the right side is affected, and it is always associated
geal nerve. It has been suggested that these communicating branches with an abnormal origin of the right subclavian artery from the aortic


may provide both additional motor components to thyroarytenoid arch on the left side. If unrecognized, a non-recurrent laryngeal nerve
and sensory fibres to the mucosa in the region of the subglottis. An may be susceptible to injury during surgery. It may also potentially be
anastomosis between the external and internal laryngeal nerves has compressed by small tumours of the thyroid gland (Friedman et al
also been described in some cases. (For further reading, see Kochilas 1986).
et al (2008).) Lesions of the vagus nerve and recurrent
The close relationship of the external laryngeal nerve to the superior
laryngeal nerve paralysis
thyroid artery puts the nerve at potential risk when the artery is clamped
during thyroid lobectomy, particularly when it is close to the artery (in The consequences of vagal nerve lesions are complex, reflecting the long
approximately 20% of cases), or where, instead of crossing the superior course of the nerve and the possible involvement of three of its branches,
thyroid vessels approximately 1 cm or more above the superior pole of namely: the pharyngeal, superior laryngeal and recurrent laryngeal
the gland, it actually passes below this point (in some 20% of cases) nerves. Collectively, these nerves innervate muscles of the larynx, soft
(Cernea et al 1992, Kierner et al 1998). The external laryngeal nerve is palate and pharynx; injury may therefore have deleterious effects on
also at risk in parathyroidectomy, carotid endarterectomy and anterior phonation and/or soft palate movements and/or swallowing. A lesion
cervical spine procedures. of the vagus above the level at which the pharyngeal branch is given off
will affect both the superior and recurrent laryngeal nerves. This causes
immobility of the vocal folds on the affected side and imparts a breathy
Recurrent laryngeal nerve
voice with lack of pitch and limited loudness. The affected cord is para-
lysed and lies in the so-called ‘cadaveric’ position halfway between
The recurrent laryngeal nerve enters the larynx by passing either deep abduction and adduction. If the lesion is unilateral, the voice is weak


to (usually) or between (sometimes) the fibres of cricopharyngeus at and hoarse, but if it is bilateral, phonation is almost absent, the vocal
its attachment to the lateral aspect of the cricoid cartilage. It supplies pitch cannot be altered, and the cough is weak and ineffective. There
cricopharyngeus as it passes. At this point, the nerve is in intimate will also be a degree of hypernasality because of the effects on move-
proximity to the posteromedial aspect of the thyroid gland. The main ments of the soft palate caused by paralysis of levator veli palatini.
trunk divides into two or more branches, usually below the lower Unilateral palsies impact very significantly on the quality of life of the
border of the inferior constrictor, although branching may occur higher patient because of impaired vocalization and a tendency to aspirate.
up. The anterior branch is mainly motor and is sometimes called the Bilateral palsies are extremely serious and a tracheostomy is required to
inferior laryngeal nerve (although this term is best avoided to prevent protect the airway. In some, a tracheal diversion procedure may become
any confusion with a former synonym for the recurrent laryngeal necessary.
nerve), while the posterior branch is mainly sensory. The anterior A lesion affecting the superior laryngeal nerve may be unilateral or
branch of the recurrent laryngeal nerve ascends posterior to the crico- bilateral. Complete section is most likely during the ligation of the
thyroid joint and its ligament, and is usually covered by fibres of pos- vessels forming the vascular pedicle of the thyroid gland during thyroid
terior cricoarytenoid at this point. It bends over the joint, continuing lobectomy. Unilateral lesions may result in the vocal folds appearing
forwards over the lateral cricoarytenoid muscle before terminating relatively normal and the effect on voice is barely noticeable and is
within thyroarytenoid. often overlooked. A more detailed examination may detect some short-
The anterior branch of the recurrent laryngeal nerve first innervates ening of the vocal folds on the affected side with asymmetric tilt of the
posterior cricoarytenoid by one or more branches, then innervates inter- epiglottis and the anterior larynx canted towards the unaffected side.