LARYNX POWERPOINT SERIES
Prepared by Dr A Horowitz
IT assistance from Mr. Paul
Orchard and Mr. Kimbel Jeffers
Equine
larynx: 5
cartilages.
A, A
1 Epiglottic,
2 Arytenoid,
1 Thyroid,
E
1 Cricoid.
T
C
Equine larynx, left lamina of thyroid
cartilage removed, showing muscles.
laryngeal ventricle
With these cartilages and muscles, the
larynx does two things:
1. Regulates the passage of air…
2. Determines the pitch of the
voice…
How does it regulate the passage of air?
• It regulates the passage of air by
changing the size of the rima glottidis
(also called “rima” or “glottic cleft”),
even closing it completely.
• What is the rima glottidis? The rima is
the diamond shaped space bounded by
the vocal folds ventrally, the mucosacovered arytenoid cartilages dorsally.
From
Budras
Atlas
mucosa of the
mucosa-covered
arytenoid cartilages
rima
glottidis
vocal folds
Epig.
arytenoid cartilages
Diagram of
the rima
glottidis,
(also called
“glottic cleft”
or “rima”)
vocal lig.
laryngeal mucosa
vocalis muscle
Vocal Fold =
vocal lig. +
vocalis
muscle +
muscosa
covering
them
Arytenoid cartilage doesn’t
stretch.
The elastic vocal ligament will.
Abduction of the vocal process
of the cartilage widens the
rima..
Resting position of the rima…
Enlarged rima with each inspiration…
Rima changes in each respiratory cycle…
The rima nearly closed…(pic from
Budras Atlas of Anatomy of the Horse)
Cricoid cartilage:
like a signet
ring, has a lamina
and an arch
articulate w/R and L
arytenoid carts.
articulate w/caudal
cornu of thyroid cart.
lamina
lamina
arch
arch
jt.
The thyroid cartilage articulating with the
cricoid…
C
vocal
process
A, A
vestib.
ligg.
T
E
vocal ligg.
Right view with right lamina of thyroid
cartilage, right half of epiglottic cart.,
and right vestibular ligament cut away.
One muscle widens the rima glottidis:
cricoarytenoideus dorsalis
cricoarytenoideus dorsalis m.
cricaryt jt med crest
musc proc
caudal cornu
arc crest
(thyroid cart)
vocal proc
medial proc
cornic
proc
Note that, in the preceding slide, as the
muscular process of the arytenoid
cartilage is drawn caudomedially by
contraction of the cricoarytenoideus
dorsalis muscle, the vocal process moves
rostrolaterally. This widens the rima in
inspiration. The muscles that close the
rima, return it to the resting position with
each expiration. These movements occur
reflexly with each respiratory cycle.
Arrows: movement of musc. and vocal procc.
vocal proc.
vocal ligg.
“body” of thyroid cart.
How the rima is closed…
1. arytenoideus
transversus contracts
2. thyroarytenoideus
contracts
3. vocal processes
adducted
The arytenoideus transversus (dorsally)
and the thyroarytenoideus (laterally and
ventrally), contracting simultaneously,
act as a sphincter, closing the rima. The
cricoarytenoideus lateralis cooperates in
this action.
How the rima is closed…
3. cricoaryt. lat.
contracts
thyroaryt. (vocalis
part, cut)
How does the larynx regulate pitch of the
voice? By changing the tension of the vocal
fold: done by contraction of the
cricothyroideus muscle, chiefly…
cricothyroideus resting
(lower pitch)
cricothyroideus m.
Cricothyroideus muscle contracting
stretches the vocal folds (only vocal ligg.
shown here)…
vocal ligg.
An animal with laryngeal dysfunction
would be expected to have difficulty
a. breathing;
b. regulating the pitch of its sound;
c. utilizing the abdominal press
(which, to be fully effective, requires that
the rima glottidis be completely closed).
Main (not the only ones) clinical
syndromes…
-laryngeal hemiplegia;
-dorsal displacement of the soft
palate (DDSP);
-epiglottic entrapment.
Laryngeal hemiplegia (paralysis of the
right or left recurrent laryngeal
nerve)…Which side is paralyzed?
Recurrent laryngeal nerve ends as the
caudal laryngeal nerve;
Supplies all laryngeal muscles except
cricothyroideus & is sensory to caudal
larynx;
Cranial laryngeal nerve or pharyngeal
branch of the vagus supplies the
cricothyroideus; chief sensory nerve.
What muscle must be paralyzed with
inability to abduct the vocal fold?
Techniques for treating laryngeal
hemiplegia:
1. Electrocautery excision of vocal fold;
2. Surg. removal of the laryngeal ventricle
with repair by elastic connective tissue;
3. Fixing the arytenoid cartilage in an
abducted position; a nonabsorbable
suture is used;
4. Nerve transplant.
In a mature horse, in normal respiration,
the larynx protrudes into the
intrapharygeal ostium.
soft palate
Figure
is from
Sisson.
DDSP:
From
Budras Atlas
of the
Anatomy of
the Horse
Palatopharyngeal arch
soft palate
Epiglottic entrapment…
aryepiglottic fold (aef)
aef extending in
front of epiglottis
aef folding over the apex
of the epiglottis
aef
The abdominal press (a physiological
mechanism to increase abdominal
pressure)…
1. Animal takes a deep breath; diaphragm
moves caudally, abdl muscles relax;
2. Rima glottidis is closed (what muscles?);
3. Abdl muscles contract (abdl pressure );
4. Rima opens (what muscles?) and animal
coughs; or rima closed, fetus expelled…
Normal larynx viewed with the
endoscope from within the nasal
pharynx…Can you I.D. the “rima”?
of nasal
pharynx
This is the roof ofAns:
theroof
nasal
pharynx.
vocal
fold
laryng. ventric.
vestibular fold
Ans: soft palate
The laryngeal ventricle: a lateral evagination
of the laryngeal mucosa; between the vocal
fold caudally, the vestibular fold rostrally. A
higher pitched sound as the mass of the vocal
fold is less.
Figure is
from
Sisson.
laryngeal ventricle
Interior of the horse’s larynx…
laryngeal ventric.
vestibular fold
vocal fold
vestibule
rima
infraglottic cavity
Cricothyroid ligament is an
important access to the larynx.
Photo taken from 5th semester diagnostic
imaging presentation on equine throat…
What’s this?
this?
this?
Be a supervet!
SWALLOWING… WHAT
HAPPENS?
RESTING PHARYNX
BOLUS DOES NOT CONTACT THE
EPIGLOTTIS, WHICH IS PUSHED
BENEATH THE ARCHING TONGUE.
In normal swallowing, the bolus does not
contact the epiglottic mucosa.
What happens if it does?
The animal coughs reflexly. Contact
of the bolus with tactile mucosal receptors
initiates the cough reflex.
What is responsible for your cough when
you swallow and the food “goes down the
wrong way”?