Download 23. larynx

Larynx
It is the organ that is responsible
for voice production and
provides a protective sphincter at
the inlet of the air passages.
Above it opens into the laryngopharynx and below it is
continuous with trachea.
It’s framework is made up of
cartilages which is connected by
membranes and ligament and
moves by muscles and is lined
by mucous membrane.
Thyroid cartilage
It consisting of 2 laminae of hyaline cartilage meeting in the midline in the Adam’s apple.
The posterior border of each lamina forms a superior and an inferior cornus
On the outer surface of each lamina is an oblique line for the attachment of the
sternothyroid, thyrohyoid and inferior constrictor muscles.
Cricoid cartilage
It is formed from complete ring of hyaline cartilage. It is shaped like a signet ring and lies
below the thyroid cartilage. It has narrow anterior arch and a broad posterior lamina.
On each side of it’s lateral surface is a facet for articulation with the inferior cornu of the
thyroid cartilage. On each side of it’s upper border is a facet for articulation with the base of
the arytenoid cartilage. These joints are synovial joints.
Arytenoid cartilages
They are two and pyramidal. They are at the
back of the larynx, on the upper border of
the lamina of the cricoid cartilage.
Each cartilage has an apex ( elastic
fibrocartilage ) above and a base ( hyaline )
below. The apex supports the corniculate
cartilage. The base articulates with the
cricoid cartilage.
Two processes project from the base. The
vocal process projects horizontally forward
and gives attachment to the vocal ligament.
The muscular process project laterally and
gives attachment to the posterior and lateral
cricoarytenoid muscles.
Corniculate cartilages
They are two small nodules ( elastic
fibrocartilage ) that articulate with the apices
of the arytenoid cartilages and give
attachment to the aryepiglottic folds.
Epiglottis
It is a leaf- shaped elastic cartilage situated behind the root of the tongue. It is connected in
front to the body of hyoid bone, and by its stalk to the back of the thyroid cartilage.
The sides of the epiglottis are connected to the arytenoid by the aryepiglottic folds.
Its upper edge is free and the covering of the mucous membrane is reflected forward onto
the posterior surface of the tongue where a median glossoepiglottic fold and lateral
pharyngo- epiglottic folds are formed. The valleculae are depressions of mucous membrane
present on either side of the median glossoepiglottic fold.
Cuneiform cartilages
They are two rod-shaped pieces of elastic fibrocartilage placed on the aryepiglottic fold and
supports this fold.
median
Membranes and Ligaments of the
larynx
1. Hyoepiglottic ligament:
It is attached to the anterior surface of the
epiglottis and the hyoid bone.
2. Thyroepiglottic ligament:
It is attached to the stalk of the epiglottis and
the back of the thyroid cartilage.
3- Thyrohyoid membrane:
It connects the upper margin of the thyroid cartilage below to the posterior surface of the
body and greater cornu of the hyoid bone above.
In the midline it is thickened to form the median thyrohyoid ligament. Its posterior borders
are thickened to form the lateral thyrohyoid ligaments.
On each side the membrane is pierced by the superior laryngeal vessels and the internal
laryngeal nerve.
4- Cricotracheal ligament:
It connects the lower margin of the cricoid cartilage to the 1st ring of the trachea.
5- Fibroelastic membrane:
It lies beneath the mucous membrane lining the larynx.
The upper portion of it is called the quadrangular membrane which extends between the
epiglottis and the arytenoid cartilages; its lower margin forms the vestibular ligaments.
The lower portion of the fibroelastic membrane is called the cricothyroid ligament. Its
anterior part is thickened and connected the cricoid cartilage to the lower margin of the
thyroid cartilage. Its lateral part is thin and is attached below to the upper margin of the
cricoid cartilage. The superior margin of this lateral part instead of being attached to the
lower margin of the thyroid cartilage it ascends within the thyroid cartilage on its medial
surface. Its upper margin is thickened and forms the vocal ligament on each side.
The anterior end of vocal cord is attached to the deep surface of the thyroid cartilage and its
posterior end is attached to the vocal process of the arytenoid cartilage.
The neck is brought forward on a pillow
( flexed at C4 to C 7) and the head is fully
extended at the atlanto-occipital joints. The
valleculae; piriform fossae; epiglottis;
aryepiglottic; vestibular; vocal cords and the 2
elevations of corniculate and
cuneiformcartilages are seen.
It looks
Inlet of the larynx
backward and upward into the
laryngeal part of the pharynx.
It’s opening is bounded in front by the upper
margin of the epiglottis ; laterally by the
aryepiglottic fold of mucous membrane which
connects the epiglottis to the arytenoid
cartilage and posteriorly and below by the
mucous membrane stretching between the
arytenoid cartilages.
Cavity of the larynx
It extends from the inlet to the lower border of
the cricoid cartilage. It is divided into 3 parts.
1- The upper part ( vestibule ):
It extends from the inlet to the vestibular
folds which are pink and project medially. The
rima vestibuli is the gap between these folds.
The vestibular ligament lies within it and
stretches from the thyroid cartilage to
arytenoid cartilage.
2- The middle part:
It extends from the level of the vestibular
folds to the level of the vocal folds. The vocal
folds are white and contain the vocal
ligaments which stretches from the thyroid
cartilage in front to the vocal process of the
arytenoid cartilage behind.
The rima glottidis is the gap between the
vocal folds in front and the vocal processes
of the arytenoid cartilages behind.
The sinus ( ventricle ) of the
larynx is a small recess between
the vestibular and vocal folds on
each side. It is lined by mucous
membrane and from it small
diverticulum ( saccule of the
larynx ) passes upward between
the vestibular fold and the
thyroid cartilage.
3- The lower part:
It extends from the level of the
vocal folds to the lower border
of the cricoid cartilage. Its wall
are formed by the inner surface
of the cricothyroid ligament and
the cricoid cartilage.
N.B:
The mucous membrane of the
larynx lines the cavity and is
covered with ciliated columnar
epithelium. On the vocal folds
the membrane is covered by
stratified squamous epithelium
where repeated trauma during
phonation occurs.
Muscles of the larynx
1- Extrinsic Muscles:
The movement of the hyoid bone is
accompanied by the movement of thyroid
cartilage ( larynx ) due to their attachment
by thyrohyoid membrane.
A- Elevators:
They include the digastric, stylohyoid,
mylohyoid and geniohyoid muscles.
The stylopharyngeus; salpingopharyngeus
and palatopharyngeus which are inserted
into the posterior border of the lamina of
the thyroid cartilage which elevate the
larynx.
B- Depressors:
They include the sternohyoid and superior
belly of omohyoid which is inserted in the
lower border of the body of hyoid bone and
the sternothyroid. The action of these
muscles is assisted by the elastic recoil of
the trachea.
2- Intrinsic Muscles of the Larynx
A- Muscles Controlling the Laryngeal Inlet
1- Aryepiglottic:
Origin: Apex of arytenoid cartilage
Insertion: Side of epiglottis
Nerve supply: Recurrent laryngeal
Action: Narrows the inlet by bringing
the aryepiglottic folds together
2- Oblique arytenoid:
Origin: Muscular process of arytenoid
cartilage
Insertion: Apex of the opposite
arytenoid cartilage
Nerve supply: Recurrent laryngeal
Action: As aryepiglottic
3- Thyroepiglottic:
Origin: Medial surface of thyroid
cartilage
Insertion: Lateral margin of epiglottis
and aryepiglottic fold
Nerve supply: Recurrent laryngeal
Action: Widens the inlet by pulling the
aryepiglottic folds apart
B- Muscles controlling the movements of vocal cords:
Recurrent laryngeal
By lateral rotation to arytenoid cartilage
Recurrent laryngeal
By medial rotation of the arytenoid cartilage
Recurrent laryngeal
Important notices:
1- There are 2 sphincters in the
larynx, one at the inlet and
other at the rima glottidis.
2- In coughing or sneezing, the
rima glottidis serves as a
sphincter. After inspiration, the
slitlike
vocal folds are adducted. After
deep inspiration, the rima
glottidis is closed.
3- The intermittent release of
expired air between the
adducted vocal folds results in
Whispering
their vibration and in the
production of sound.
7- A grunting sound is produced due to release some of
the air by momentarily opening of the rima glottidis. 4- The quality of the voice depend
on the resonators above the
8- The sphincters at the inlet is used only during
larynx, namely, the pharynx;
swallowing. As the bolus of food is passed backward
mouth and paranasal sinuses.
between the tongue and the hard palate, the larynx is 5- In quiet respiration, the rima
pulled up beneath the back of the tongue. The inlet is
glottidis is triangular with the
narrowed and the epiglottis is pushed backward by
apex in front.
the tongue and serves as a cap over the laryngeal
6- With forced inspiration, the rima
inlet. The bolus now enters the esophagus by passing glottidis is diamond shape
over the epiglottis or moving down the grooves on
because of the lateral rotation of
either side of the laryngeal inlet ( Piriform fossae )
the arytenoid cartilages.
causing coughing.
Blood supply and lymph drainage
The upper half of the larynx is supplied by the superior laryngeal branch of the superior
thyroid artery which is a branch from the external carotid artery..
The lower half of the larynx is supplied by the inferior laryngeal artery a branch of the
inferior thyroid artery which is a branch from the thyrocervical trunk of the 1st part of the
subclavian artery.
The lymph vessels drain into laryngeal lymph nodes which lie on the front of the
cricothyroid and thyrohyoid membranes and drain into the deep cervical group of nodes.
Nerve Supply
*
The sensory nerve supply to
the mucous membrane of the
larynx above the vocal fold is
from the internal laryngeal
branch of the superior
laryngeal branch of the vagus.
Below the level of the vocal
folds, the mucous membrane
is supplied by the recurrent
laryngeal nerve.
The motor nerve supply to the
intrinsic muscles of the larynx
is the recurrent laryngeal
nerve ,except for the
*cricothyroid muscle which is
supplied by the external
laryngeal branch of the
superior laryngeal branch of
the vagus.
Lesion of laryngeal nerves
Both recurrent laryngeal and external laryngeal nerves can be injured during
operation of thyroid gland.
Both recurrent laryngeal nerves may be damaged by malignancy of the deep
cervical lymph nodes.
The left recurrent laryngeal nerve may be involved in a bronchial; esophageal
carcinoma or in secondary metastatic deposits in the mediastinal lymph nodes.
Weakness of voice (vocal cord cannot be tensed)
due to paralysis of cricothyroid muscle.
Breathing and speech is not greatly
affected. The position between
adduction and abduction.
Speech is lost but breathing is impaired
Greater degree of paralysis of the abductor than
adductor. The affected vocal cord assumes the
adducted midline position.
Acute dyspnea and stridor. Cricothyroidotomy or
tracheostomy is necessary.