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posterior is broad, triangular, and concave from above downwards, lodging part of
the arytenoid muscle. The anterior, or external, has a transverse ridge situated at
about the junction of its lower and middle thirds ; above and below this the surface
is concave. The false vocal cord is attached near the inner end of the ridge, and the
thyro-arytenoideus is inserted into the depressions and outer part of the ridge. The
internal surface, which is the narrowest of the three, and slightly convex, is nearly
parallel with that of the opposite cartilage, and is covered by the laryngeal mucous
membrane. The anterior and posterior borders, which limit the internal face, are
nearly vertical, whilst the external border, which separates the anterior from the
posterior surface, is oblique.

The base of each arytenoid cartilage is slightly hollowed, having towards its outer
part a smooth concave surface for articulation with the cricoid cartilage. Two of its



CARTILAGES OF THE LARYNX. 149

angles are remarkably prominent, viz., one external, short, and rounded, which
projects backwards and outwards, and into which the posterior and the lateral
crico-arytenoid muscles are inserted (muscular process} : the other anfefwr^which is
more pointed, and forms a horizontal projection forwards, to which the corre-
sponding true vocal cord is attached (vocal process).

The apex curves backwards and a little inwards, and terminates in a blunt point,
which is surmounted by the corniculum laryngis.

A small cartilaginous nodule (sesamoid cartilage) is sometimes found at the outer aide of
the arytenoid near the tip, embedded in the perichondrium.

The cornicula laryngis, or cartilages of Santorini, are two small yellowish
cartilaginous nodules of a somewhat conical shape, which are articulated with the
summits of the arytenoid cartilages (fig. IGitfi), and serve, as it were, to prolong them
backwards and inwards. They sometimes form part of the arytenoid cartilage?.

The cuneiform cartilages, or cartilages of Wrisberg, are two very small,
soft, yellowish, cartilaginous bodies, placed, one on each side, in the fold of the
mucous membrane which extends from the summit of the arytenoid cartilage to the
epiglottis. They have a conical form, with the base directed upwards. They
occasion small elevations of the mucous membrane, a little in advance of the
cornicula, with which, however, they are not directly connected.

These cartilages are very frequently absent, especially in the white races of mankind, but
according- to Gibb are always present in the negro.

The epiglottis (fig. 169B, 7) is a median lamella of yellow cartilage, shaped
somewhat like an obovate leaf, and covered by mucous membrane. It is placed in
front of the superior opening of the larynx, projecting, in the ordinary condition,
upwards immediately behind the base of the tongue.

The cartilage of the epiglottis is broad and rounded at its upper free margin, but
below it becomes pointed, and is prolonged by means of a long, narrow, elastic
band (the thyro-epiglottic ligament] to the deep angular depression between the alae
of the thyroid cartilage, to which it is attached behind and below the median notch.
Its lateral borders, which are convex and turned backwards, are only partly free, the
lower parts being enveloped in the aryteno-epiglottic folds of mucous membrane.
The anterior or lingual surface is free only in its upper part, where it is covered by
mucous membrane. Lower down, the membrane is reflected from it forwards to the
base of the tongue, forming three folds or fnenula, the middle and lateral glosso-
epiglottic folds. This surface is also connected below with the posterior surface of
the hyoid bone by a median elastic structure named the hyo-epiglottic ligament.
The posterior or laryngeal surface, which is free in the whole of its extent, is
concavo-convex from above downwards, but concave from side to side ; the convexity
projecting backwards into the larynx is named the tubercle or cushion. The
epiglottis is closely covered by mucous membrane, on removing which the yellow
cartilaginous lamella is seen to be pierced by numerous little pits and perforations, in
which are lodged small glands, which open on the surface of the mucous membrane.

Structure of the cartilages of the larynx. The epiglottis, the cornicula
laryngis, and the cuneiform cartilages are composed of elastic or yellow fibro-
cartilage, and have no tendency to ossify. The apices of the arytenoid
cartilages are also formed of elastic fibre-cartilage, but the greater part of these, as
well as the cricoid and thyroid cartilage, are composed of hyaline cartilage,
resembling generally that of the costal cartilages, like which, they are very prone to
ossification as life advances.

Peculiarities of the larynx according to age and sex. In the foetus
the larynx is considerably higher in relation to the vertebral column than in the



150



ORGANS OF RESPIRATION AND VOICE.



adult. Thus, in the sixth month of foetal life the upper end of the epiglottis
is opposite the anterior arch of the atlas and the lower border of the cricoid
cartilage, at the level of the middle of the body of the fourth cervical, the whole
larynx being thus fully two vertebrae higher than in adult life. Until puberty the
larynx gradually descends, by which time it has attained its adult position. This
descent of the larynx is, therefore, independent of the special increase in size of the
organ occurring at puberty, and appears to be associated with the growth in a vertical
direction of the facial part of the skull, which is relatively very small in the foetus.

Up to the age of puberty the larynx is similar in the male and female, the
chief characteristics at that period being the small size and comparative slightness of
the organ, and the smooth rounded form of the thyroid cartilage in front. In the
female these conditions are permanent, excepting that a slight increase in size takes
place. In the male, on the contrary, at the time of puberty, remarkable changes
rapidly occur, and the larynx becomes more prominent and more perceptible at the
upper part of the neck. Its cartilages become larger, thicker, and stronger, and the
alae of the thyroid cartilage project forwards in front so as to form at their union






B



C



Fig. 170. Views OF THYROID, CRICOID, AND ARYTENOID CARTILAGES PARTIALLY OSSIFIED. PORTION

OSSIFIED SHADED. (Chievitz.)

The relative proportions of the three cartilages are not kept in this figure.

A, thyroid cartilage, with inferior cornu and adjacent part of ala ossified ; B, cricoid cartilage
ossified at upper part : C, arytenoid almost completely ossified.

with one another the prominent ridge of the pomum Adami. At the same time, the
median notch on its upper border is considerably deepened. In consequence
of these changes in the thyroid cartilage, the distance between its angle in front and
the arytenoid cartilages behind becomes greater, and the vocal cords are necessarily
lengthened. Hence the dimensions of the glottis, which, at the time of puberty,
undergo an increase of about one-third only in the female, are nearly doubled in the
male, and the adult male larynx becomes altogether one-third larger than that of the
female.

Taguchi found that the average distance from the upper border of the thyroid
cartilage to the lower border of the cricoid, measured in the median plane, was in
39 males 4*8 cm. and in 33 females 3'8 cm.

Ossification of the cartilages of the larynx. At about twenty years of age
ossification usually begins in the thyroid and cricoid cartilages, and a few years later in the
arytenoids. In the thyroid cartilage ossification takes place first near the inferior cornu, and
this is speedily followed by the appearance of a median nucleus in the angle between the
alae ; from the lower cornu the ossification extends along the inferior and posterior borders,
and thence spreads through the ala. The cricoid cartilage first becomes ossified at its upper
border on each side, near the arytenoid and thyroid articular facets, and the bony masses of
the two sides soon become united across the back of the ring ; the lower border remains
cartilaginous for some time longer. The arytenoid cartilages become ossified from below
upwards. The ossification begins somewhat earlier and proceeds more rapidly in the male
than in the female (J. H. Chievitz, Arch. f. Anat., 1882.)



LIGAMENTS OF THE LARYNX. 151

The cricoid and the arytenoids are the most primitive of the laryngeal cartilages, being: found
in connection with the air-passages of certain of the amphibia, and also in the reptilia, while
the thyroid and the epiglottis, at least in a well-developed condition, are peculiar to mammals.
The thyroid cartilage represents the ventral remains of the skeleton of two paTra "of visceral
arches (4th and oth), united by a median plate. In the ornithorhynchus these five parts of
the thyroid can be recognized as distinct elements, but in the higher mammalia they are more
or less blended. In man the two cornua of each ala represent ununited parts of the two
arches, while the peculiarities in appearance and structure of the isthmus as compared with
the alas indicate the median portion uniting the arches. According to Dubois the epiglottis
represents a chondrification in the submucosa of the glosso-laryngeal fold, the cartilages of
Wrisberg being formed in a similar manner in the false cords. Gegenbaur maintains, how-
ever, that the epiglottis is an independent element of the skeleton, derived from the sixth pair
of visceral arches, and according to Goppert, the cartilages of Wrisberg are formed from the
lateral processes of the primitive epiglottis. Small cartilaginous nodules are sometimes found
behind or between the arytenoids, which are the rudiments of the pro-cricoids.

LIGAMENTS AND JOINTS OF THE LABYNX.

The larynx is connected with the hyoid bone by a broad membrane, and at the
sides of this by two round lateral ligaments. The thyro-hyoid membrane, or
middle thyro-hyoid ligament (fig. 168, 5), is a broad, fibrous, and somewhat
elastic membrane, which passes up from the whole length of the superior border
of the thyroid cartilage to the hyoid bone, where it is attached to the posterior and
upper margin of the obliquely inclined inferior surface. Owing to this arrange-
ment, the top of the larynx, when drawn upwards, is permitted to slip within the
circumference of the hyoid bone, between which and the upper part of the thyroid
cartilage there is found a small synovial bursa. The thyro-hyoid membrane is thick
where subcutaneous towards the middle line, but at the sides becomes thin and loose,
and is covered by the thyro-hyoid muscles. Behind is the epiglottis, with the
mucous membrane of the base of the tongue, separated, however, by adipose tissue
and mucous glands. This ligament is perforated by the superior laryngeal artery
and nerve of each side. The lateral thyro-hyoid ligaments (fig. 168, 6), placed
at the posterior limits of the thyro-hyoid membrane, are two rounded yellowish
cords, which pass up from the superior cornua of the thyroid cartilage, to the
extremities of the great cornua of the hyoid bone. They are distinctly elastic, and
there is frequently enclosed in each a small oblong cartilaginous nodule, which has
been named cartilago triticea; sometimes this nodule is bony.

The thyroid and cricoid cartilages are connected together by a membranous
ligament and syuovial articulations. The crico-thyroid membrane (fig. 168, 9) is
divisible into a median and two lateral portions. The median portion, broad below
and narrow above, is a strong, triangular, yellowish ligament, consisting chiefly of
elastic tissue, and is attached to the contiguous borders of the two cartilages. Its
anterior surface is convex, is partly covered by the crico-thyroid muscles, and is
crossed horizontally by a small auastomotic arterial arch, formed by the junction of
the crico-thyroid branches of the right and left superior thyroid arteries. The
lateral portions are fixed on each side along the inner edge of the upper border of the
cricoid, close under the mucous membrane ; they become much thinner above, where
they are continuous with the inferior thyro-arytenoid ligaments.

The crico-thyroid articulations, between the inferior coriiua of the thyroid
cartilage and the sides of the cricoid, are two small but distinct joints, having each a
ligamentous capsule and a synovial membrane. The prominent oval articular
surfaces of the cricoid cartilage are directed upwards and outwards, while those of
the thyroid cartilage look in the opposite direction. The capsular fibres form
a stout baud behind the joint. The movement allowed is of a rotatory description,
the axis of rotation passing transversely through the two joints. In addition,
a slight gliding movement forwards and backwards may occur.



5 ORGANS OF RESPIRATION AND VOICE.

The superior thyro-arytenoid ligaments consist of a few slight fibrous
fasciculi, contained within the folds of mucous membrane forming the false vocal
cords hereafter to be described, and are fixed in front to the angle between the alee
of the thyroid cartilage, somewhat above its middle, and close to the attachment of
the epiglottis ; behind, they are connected to the inner part of the ridges on the
anterior surface of the arytenoid cartilages. They are continuous above with
scattered fibrous bundles contained in the aryteno-epiglottic folds.

The inferior thyro-arytenoid ligaments are formed of fine closely arranged
elastic fibres, which are attached in front to the middle of the angle between the alse
of the thyroid cartilage, and behind to the anterior projection of the base of the
arytenoid cartilages. The inner edge of each ligament is free and sharply defined
between those attachments, and, covered by the mucous membrane, forms the true
vocal cord of its own side. In other directions these ligaments are less sharply
defined, for in their outer part they spread out both above and below as they pass
backwards. Above, the fibres of the ligament lie near the upper surface of the
projecting fold of mucous membrane which bounds the rima glottidis, and become
gradually merged into the elastic tissue of that membrane. Below, the inferior
thyro-arytenoid ligament passes in continuity with the lateral crico-thyroid
ligament, so that it may be described as an upward extension of this ligament, and
the vocal cord may be stated to be formed by the superior free edge of the crico-
thyroid membrane.

The crico-arytenoid articulations are surrounded by a series of thin capsular
fibres, which, together with a loose synovial membrane, serve to connect the convex
elliptical articular surfaces on the upper border of the cricoid cartilage with
the concave articular depressions on the bases of the arytenoid cartilages. The
articular surface on the arytenoid cartilage is longer from before back than from side
to side ; so that its long axis crosses that of the corresponding surface on the
cricoid, and a part of the latter surface is in every position of the arytenoid
left uncovered (Henle). The movements allowed are of two kinds, viz.: 1. a
lateral gliding movement from within out or vice versa, the arytenoid cartilage being
bodily moved away from or towards its fellow ; 2. a rotating movement on a nearly
vertical axis, the vocal processes being inclined inwards or outwards (as well as
somewhat downwards or upwards). A combined rotating and gliding movement
may also occur. The ordinary position of the arytenoid, when the larynx is at rest,
is on the outer part of the articular surface on the cricoid. There is a strong
crico-arytenoid ligament, arising from the cricoid, and inserted into the inner
and back part of the base of the arytenoid cartilage.

The summits of the arytenoid cartilages and the cornicula laryngis are
sometimes united by a synovial joint, but most frequently by connective tissue
forming a sort of syndesmosis.

INTERIOR OF THE LARYNX.

The cavity of the larynx is divided into an upper and a lower compartment by
the comparatively narrow aperture of the glottis, or rima glottidis, the margins of
which, in their anterior two-thirds, are formed by the lower or trite vocal cords ; and
the whole laryngeal cavity, viewed in transverse vertical section (fig. 171) thus
presents the appearance of an hour-glass. The upper compartment, often called
the vestibule, communicates with the pharynx by the superior aperture of the
larynx, and contains immediately above the rima glottidis the ventricles (s), with
their pouches or saccules(s'\ and the upper or false vocal cords. The lower compart-
ment passes inferiorly into the tube of the windpipe] without any marked con-
striction or limitation between them. The whole of the interior of the larynx is
lined by mucous membrane.



INTERIOR OF THE LARYNX.



153



The superior aperture of the larynx, when open, is triangular, wide in front
and narrow behind, the lateral margins sloping obliquely downwards and backwards.
It is bounded in front by the epiglottis (fig. 173, A, e, and fig. 174, afi behind by
the summits of the arytenoid cartilages (fig. 173, B, a) and cornicula (s), with the
angular border of mucous membrane crossing the median space between them, and
on the sides by two folds of mucous membrane, the aryteno-epigloitic folds, which,
enclosing a few ligamentous and muscular fibres and the cuneiform cartilages





Fig. 171. ANTERIOR HALF OF A CORONAL SUCTION THROUGH THE LARYNX NEAR ITS MIDDLE.

(Allen Thomson.)

1, upper division of the lavyngeal cavity ; 2, central portion ; 3, lower division, continued into 4,
trachea ; e, the free part of the epiglottis ; c', its cushion ; h, great cornu of the hyoid bone ;
lit, thyro-hyoid membrane ; t, thyroid cartilage ; c, cricoid cartilage ; r, first ring of the trachea ;
ta, thyro-aryteuoid muscle ; vl, inferior thyro-arytenoid ligament in the membrane of the true vocal cord
at the rima glottidis ; a, the ventricle ; above this, the superior or false cords ; s', the sacculus or
pouch opened on the right side by carrying the section further forward.

Fig. 172. VIEW OF THE INTERIOR OF THE RIGHT HALF OF THE LARYNX. (Sappey.)
1, ventricle ; 2, superior, and 3, inferior vocal cord ; 4, arytenoid cartilage covered by mucous
membrane ; 5, arytenoid muscle cut across ; 6, slope of crico-thyroid membrane lea ling up to inferior
vocal cord ; 7, 8, sections of cricoid ; 9, its upper border ; 9', its lower border ; 10, section of
thyroid ; 11, upper part of larynx ; 12, 13, glandular prominence in ary.-epiglottic fold ; 14, 16,
epiglottis ; 15, fat between it and the thyro-hyoid membrane ; 17, section of epiglottis ; 18, section of
hyoid bone ; 19, 20, trachea.

(fig. 173, B, w), pass forwards from the tips of the arytenoid cartilages and cornicula
to the lateral margins of the epiglottis (fig. 174, 8, 9, 10).

In studying the form of the laryngeal cavity and its apertures, it is well to become
acquainted with the appearances which they present on examination during life by means of
the laryngoscope, and with the relations of these to the anatomical structure. On thus
examining the superior aperture, there are seen on each side two rounded elevations
(fig. 173. A. B, #, u>), corresponding respectively to the cornicula and the cuneiform cartilages :



154



ORGANS OF RESPIRATION AND VOICE.



while in the middle line in front there is a tumescence of the mucous membrane on the lower
part of the epiglottis, named the tubercle or cushion of the tyiglottis (c).

When the superior aperture is closed during the act of deglutition, it presents,
according to Anderson Stuart, a T-shaped fissure. The transverse limb of the
T is slightly curved, with the convexity forwards, and is bounded in front by the
epiglottis, and behind by the aryteno-epi glottic folds. The vertical limb of the
T is represented by a median fissure, extending from the epiglottis in front to the
interarytenoid fold behind, and bounded at the sides by the arytenoid cartilages.

On looking down through the superior opening of the larynx, the glottis or rima
glottidis (fig. 173, and fig. 174, c} is seen at some distance below, in the form of a
long narrow fissure running from before backwards. It is situated on a level with
the lower part of the arytenoid cartilages, and is bounded by the true vocal cords.
Above the glottis another pair of projecting folds is seen, the superior or false



A'



Fig. 173. THREE LARYNGOSCOPIC VIEWS OP

THE SUPERIOR APERTURE OF THE
LARYNX AND SURROUNDING PARTS IN DIF-
FERENT STATES OF THE GLOTTIS DURING

LIFE. (From Czermak.)

A, the glottis during the emission of a
high note in singing. B, in easy or quiet
inhalation of air. C, in the state of widest
possible dilatation, as in inhaling a very
deep breath. The diagrams A', B', C' have
been added to Czermak's figures to show in
horizontal sections of the glottis the position
of the vocal ligaments and arytenoid car-
tilages in the three several states represented
in the other figures. In all the figures, so
far as marked, the letters indicate the parts
as follows, viz. : I, the base of the tongue ;
c, the upper free part of the epiglottis ; e',
the tubercle or cushion of the epiglottis ;
p h, part of the anterior wall of the pharynx
behind the larynx ; in the margin of the
avyteno-epiglottidean fold w, the swelling of
the membrane caused by the cuneiform
cartilage ; s, that of the corniculum ; a,
the tip of the arytenoid cartilages ; c v, the
true vocal cords or lips of the rima glottidis ;
c v s, the superior or false vocal cords ; be-
tween them the ventricle of the larynx ;
in C, t r is placed on the anterior wall of the
receding trachea, and 6 indicates the com-
mencement of the two bronchi beyond the
bifurcation, which may be brought into view in this state of extreme dilatation.

vocal cords, which are much less projecting than the inferior. Between the superior
and inferior vocal cords the sinus or ventricle is seen as an elongated depression
(fig. 174, V).

The superior vocal cords or ventricular bands, also called the false vocal
cords, because they are not immediately concerned in the production of the voice,
are prominent rounded folds of mucous membrane enclosing very numerous glands
which form somewhat arched projections, immediately above the corresponding
ventricle (fig. 174, b). The latter is seen on looking down into the laryngeal cavity,
the superior vocal cords (fig. 173, cvs,} being further apart than the inferior (cv).

Wylie showed (Edin. Med. Journal, 1866) that when the false vocal cords are simply
approximated and air is injected into the larynx from below, they prevent the exit of the air,
and he held that the closure of the glottis in defascation and vomiting 1 is mainly effected by
the apposition of the false cords. His experiments have been confirmed by Brunton and
Cash.




VOCAL CORDS.



155



The inferior or true vocal cords,, the structures by the vibration of which the
sounds of the voice are produced, bound the anterior two-thirds of the aperture

Fig. 174. PERSPECTIVE VIEW OF THE PHARYNGEAL

OPENING INTO THE LARYNX FROM ABOVE AND

BEHIND. (Allen Thomson.)

The superior aperture has been much dilated ; the
glottis is in a moderately dilated condition ; the wall of
the pharynx is opened from behind and turned to the
sides. 1, body of the hyoid bone ; 2, small cornua ; 3,
great cornua ; 4, cornua of the thyroid cartilage ; 5,
membrane of the pharynx covering the posterior surface
of the cricoid cartilage ; 6, gullet ; 7, trachea ; 8, pro-
jection caused by the cartilage of Santorini ; 9, the
same belonging to the cartilage of Wrisberg ; 10,
aryteno-epiglottic fold ; 11, cut margin of the wall
of the pharynx ; a, free part of the epiglottis ; a', its
lower pointed part ; a", the cushion ; b, eminence on
each side over the sacculus or pouch of the larynx ; V,
the ventricles ; c, the glottis ; the lines on each side
point to the vocal cords.

of the glottis, corresponding with the thyro-
arytenoid ligaments (fig. 174, c) . The mucous
membrane covering them is so thin and
closely adherent as to show the yellowish
colour of the ligaments through it. They are
situated at the inner and free edge of a mass
of tissue triangular on coronal section (fig.
171). One surface of this mass looks up-
wards, and forms the floor of the ventricle,
another looks downwards and inwards, and "'

bounds the lower division of the laryngeal cavity, while the third is external.

A small nodule of elastic cartilage (cartilage of Luschka) is found in the anterior



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