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Larynx & Trachea
Head & Neck Unit – Lecture 14
‫ حيدر جليل األعسم‬.‫د‬
Larynx
Larynx is an organ that is responsible for voice production. It is situated
below the tongue and hyoid bone and between great blood vessels of the
neck and lies at the level of 4th, 5th & 6th cervical vertebrae. It opens above
into laryngeal part of pharynx, and below is continuous with trachea.
Larynx is covered in front by infrahyoid muscles and laterally by thyroid
gland. Framework of larynx is formed of cartilages that are held together by
ligaments & membranes, moved by muscles & lined by mucous membrane.
Cartilages of the Larynx
1. Thyroid cartilage: is largest cartilage of larynx and
consists of 2 laminae of hyaline cartilage that meet
in midline in the prominent V angle (Adam's apple).
Its posterior border extends upward into Superior
Cornu &downward into Inferior Cornu.Lamina outer
surface has Oblique Line for muscles attachment.
2. Cricoid cartilage: is formed of hyaline cartilage
like signet ring with broad Lamina behind & shallow
arch in front. Its lamina has a facet for articulation
with inferior cornu of thyroid cartilage & another
facet for articulation with arytenoid cartilage on
upper border of cricoid lamina, posteriorly.
3. Arytenoid cartilages: are 2 small pyramidal
shaped cartilages located at back of larynx. Each has
Apex: above, articulates with corniculate cartilage
Base: below, articulates with cricoid lamina
Vocal process: projects forward for vocal ligament
Muscular process: projects laterally for attachment
of posterior & lateral cricoarytenoid muscles.
Cartilages of the Larynx
4. Corniculate cartilages: are 2 small
conical-shaped cartilages that articulate
with Arytenoid Cartilages and give
attachment to Aryepiglottic Folds.
5. Cuneiform cartilages: are 2 small rodshaped cartilages in the Aryepiglottic folds
to strengthen them.
6. Epiglottis: is leaf-shaped lamina of
elastic cartilage lies behind root of
tongue. Its stalk is attached to back of
thyroid cartilage and its sides are attached
to arytenoid cartilages by Aryepiglottic
folds. Its upper edge is free and its mucous
membrane covering passes forward onto
posterior surface of tongue as median
glossoepiglottic fold; while the depression
on each side of this fold is called vallecula.
Laterally the mucous membrane passes
onto the wall of the pharynx as Lateral
glossoepiglottic fold.
Membranes and Ligaments of Larynx
Thyrohyoid membrane: connects upper margin of
thyroid cartilage to hyoid bone. In the midline it is
thickened to form median thyrohyoid ligament. It is
pierced on each side by superior laryngeal vessels
and internal laryngeal nerve.
Cricotracheal ligament: connects cricoid cartilage to
first ring of trachea.
Quadrangular membrane: extends between
epiglottis and arytenoid cartilages. Its thickened
inferior margin forms vestibular ligaments.
Cricothyroid ligament: is attached to upper border
of cricoid cartilage (inferiorly) & ascends on medial
surface of thyroid cartilage. Its upper free border is
composed entirely of elastic tissue and forms the
important vocal ligament on each side. Vocal
ligaments form interior of vocal folds (vocal cords).
Vocal ligaments are attached to thyroid cartilage
anteriorly, and to vocal process of arytenoid cartilage
posteriorly.
Inlet of the Larynx
The inlet of the larynx looks backward
and upward into laryngeal part of
pharynx. It is wider anteriorly than
posteriorly and is bounded:
Anteriorly by epiglottis
Laterally by aryepiglottic fold
Posteriorly by arytenoid cartilages with
corniculate cartilages. Cuneiform
cartilage lies within and strengthens
aryepiglottic fold and produces a small
elevation on its upper border.
Piriform Fossa:
It is a recess on either side of aryepiglottic
fold and laryngeal inlet. It is bounded
Medially: by aryepiglottic fold and
Laterally: by thyroid cartilage and
thyrohyoid membrane.
Laryngeal Folds
Vestibular Fold: is a fixed fold on each
side of larynx and is formed by mucous
membrane covering vestibular ligament
and is vascular and pink in color.
Vocal Fold (Vocal Cord): is a mobile fold
on each side of larynx and is concerned
with voice production. It is formed by
mucous membrane covering vocal
ligament and is avascular and white in
color.
The gap between vocal folds is called
rima glottidis or glottis. Glottis is the
narrowest part of larynx in adults and is
bounded in front by vocal folds and
behind by medial surface of arytenoid
cartilages. In children lower part of
larynx within cricoid cartilage is the
narrowest part.
Cavity of the Larynx
It extends from inlet to lower border of
cricoid cartilage. It is divided into 3 regions:
Vestibule: is situated between inlet and
vestibular folds.
Middle region: is situated between
vestibular folds above and vocal folds below.
Lower region: is situated between vocal
folds above and lower border of cricoid
cartilage below.
Sinus of the Larynx: (Laryngeal Ventricle)
It is a small recess on each side of larynx
between vestibular & vocal folds and is lined
by mucous membrane.
Saccule of the Larynx:
It is a diverticulum of mucous membrane
that ascends from the sinus. Mucous
secretion lubricates vocal cords
Muscles of the Larynx
Extrinsic Muscles: move larynx up and down during
swallowing and because many of them are attached
to hyoid bone, which is attached to thyroid cartilage
by thyrohyoid membrane.
Elevation: digastric, stylohyoid, mylohyoid,
geniohyoid, stylopharyngeus, salpingopharyngeus,
and palatepharyngeus muscles.
Depression: sternothyroid, sternohyoid & omohyoid.
Intrinsic Muscles:
Two muscles modify laryngeal inlet:
Narrowing inlet: oblique arytenoid muscle.
Widening inlet: thyroepiglottic muscle.
Five muscles move vocal folds (cords):
Tensing vocal cords: Cricothyroid muscle.
Relaxing vocal cords: Thyroarytenoid (vocalis) muscle
Adducting vocal cords: Lateral cricoarytenoid muscle
Abducting vocal cords: Posterior cricoarytenoid m
Approximates arytenoid cartilages: Transverse
arytenoid muscle.
Movements of the Vocal Folds (Cords)
Movements of vocal folds depend on
movements of arytenoid cartilages, which
rotate and slide up and down on sloping
shoulder of superior border of cricoid cartilage.
Rima glottidis is opened by contraction of
posterior cricoarytenoid, which rotates
arytenoid cartilage and abducts vocal process.
Elastic tissue in the capsules of cricoarytenoid
joints keeps arytenoid cartilages apart so that
posterior part of glottis is open.
Rima glottidis is closed by contraction of
lateral cricoarytenoid, which rotates arytenoid
cartilage and adducts vocal process.
Posterior part of glottis is narrowed when
arytenoid cartilages are drawn together by
contraction of transverse arytenoid muscles.
Vocal folds are stretched by contraction of
cricothyroid muscle.
Vocal folds are slackened by contraction of
vocalis, a part of thyroarytenoid muscle.
Sphincteric Function of Larynx
There are two sphincters in the larynx:
A. Sphincter at the inlet is used only
during swallowing. (to close the inlet
and prevent inhalation of food)
B. Rrima glottidis serves as a sphincter
during coughing or sneezing (narrowing
of glottis). While in Valsalva maneuver,
forced expiration takes place against a
closed glottis. In abdominal straining
associated with micturition and
defecation, air is often held temporarily
in respiratory tract by closing rima
glottidis.
Nerve Supply of the Larynx
Sensory Nerves:
Above vocal cords: Internal
laryngeal branch of superior
laryngeal branch of vagus.
Below vocal cords: Recurrent
laryngeal nerve.
Motor Nerves:
All intrinsic muscles of larynx except
cricothyroid muscle are supplied by
recurrent laryngeal nerve.
Cricothyroid is supplied by external
laryngeal branch of superior
laryngeal branch of vagus.
Blood Supply of the Larynx
A. Upper half of larynx:
Superior laryngeal branch of
superior thyroid artery.
B. Lower half of larynx:
Inferior laryngeal branch of
inferior thyroid artery.
Lymph Drainage of the Larynx:
Deep cervical lymph nodes.
The Trachea
It is a mobile cartilaginous & membranous
tube. It begins at the level of 6th cervical
vertebra & descends in midline of neck.
Trachea is kept patent by presence of Ushaped cartilaginous bar (rings) of hyaline
cartilage embedded in its wall. Posterior free
ends of cartilages are connected by smooth
muscle (trachealis muscle).
Relations of Trachea in the Neck:
Anteriorly: Skin, fascia, isthmus of thyroid
gland (2nd, 3rd & 4th rings), inferior thyroid
vein, jugular arch, thyroidea ima artery, and
left brachiocephalic vein in children,
overlapped by sternothyroid and
sternohyoid.
Posteriorly: Right and left recurrent
laryngeal nerves and esophagus.
Laterally: Lobes of thyroid gland and carotid
sheath and contents.
Nerve Supply of Trachea:
Sensory nerve supply is from
vagus & recurrent laryngeal
nerves.
Blood Supply of Trachea:
Upper 2/3 is supplied by
inferior thyroid arteries and
lower 1/3 is supplied by
bronchial arteries.
Lymph Drainage of Trachea:
Pretracheal & Paratracheal
lymph nodes and deep
cervical nodes.
Vagus Nerve
It is composed of motor and sensory fibers and leaves skull
through jugular foramen. It descends through the neck
alongside carotid arteries and internal jugular vein within
carotid sheath. It passes through mediastinum of thorax,
passing behind root of lung, and enters abdomen through
esophageal opening in the diaphragm.
Important Branches of the Vagus Nerve in the Neck:
1.Meningeal and auricular branches.
2.Pharyngeal branch: joins pharyngeal plexus & supplies
all muscles of pharynx (except stylopharyngeus) and of soft
palate (except tensor veli palatini).
1.Superior laryngeal nerve: divides into internal and
external laryngeal nerves. External branch is closely related
to superior thyroid artery.
1.Recurrent laryngeal nerve:
On Right side, it hooks around first part of subclavian artery.
On the left side, it hooks around arch of aorta.
It is closely related to inferior thyroid artery and it supplies
all muscles of larynx (except cricothyroid), mucous
membrane of larynx below vocal cords and mucous
membrane of upper trachea.
5.Cardiac branches (two or three) arise in the neck, descend
into thorax, and end in cardiac plexus.
End of the Lecture
GOOD LUCK