anatomy of larynx

IMS MSU

Dr. THAAER MOHAMMED DAHER ALSAAD

SPECIALIST IN GENERAL SURGERY

M.B.Ch.B.(MBBS) F.I.B.M.S.(Ph.D.)

SENIOR LECTURER

Movements of the Larynx during Swallowing During swallowing the elevation of the larynx folds the epiglottis over the glottis, steering materials into the esophagus

Muscles that form the floor of the oral cavity, superior view

Origins and insertions on the mandible and hyoid

THE LARYNX

ANATOMY

OUTLINES

• Introduction.• Cartilages.• Ligaments.• Sound production.• Muscles.• Associated terms.• Blood supply.• Nerve supply.• Lymphatic drainage.• Cricothyroidotomy + tracheostomy.

LARYNX• 9 CARTILAGES.

–3 PAIRED

–3 UNPAIRED

• 8 MUSCLES.

• LIGAMENTS

LARYNX • It is the musculocartilaginous structure,• lined with mucous membrane,• connected to the superior part of the trachea and to

the pharynx.

• inferior to the tongue and the hyoid bone;

• the essential sphincter guarding the entrance into the trachea.

• functioning secondarily as the organ of voice.

• It is formed by nine cartilages connected by ligaments and eight muscles.

The Larynx

Inspired (inhaled) air leaves the pharynx by passing through a narrow opening, the glottis.

The larynx begins at the level of vertebra C4 or C5and ends at the level of vertebra C7.

It is essentially a cylinder whose cartilaginous walls are stabilized by ligaments or skeletal muscles or both.

External view of the larynx: (a) anterior aspect; (b) anterolateral aspect.

Cartilages of the Larynx

Three large unpaired cartilages form the body of the larynx:

the thyroid cartilage,

the cricoid cartilage,

the epiglottis.

The thyroid and cricoid cartilages are hyaline cartilages;

the epiglottic cartilage is an elastic cartilage

The Thyroid Cartilage The largest laryngeal cartilage is the thyroid (“shield-shaped”) cartilage. It forms most of the anterior and lateral walls of the larynx . The thyroid cartilage, when viewed in sagittal section, is incomplete

posteriorly. The anterior surface of this cartilage bears a thick ridge, the laryngeal

prominence. This ridge is easily seen and felt, and the thyroid cartilage is commonly

called the Adam’s apple. During embryological development, the thyroid cartilage is formed by

two pieces of cartilage that meet in the anterior midline to form the laryngeal prominence.

The inferior surface of the thyroid cartilage articulates with the cricoid cartilage;

the superior surface has ligamentous attachments to the epiglottis and smaller laryngeal cartilages.

The Cricoid Cartilage The thyroid cartilage sits superior to the cricoid “ring-

shaped”) cartilage. It is a complete ring whose posterior portion is greatly

expanded, providing support in the absence of the thyroid cartilage.

The cricoid and thyroid cartilages protect the glottis and the entrance to the trachea,

and their broad surfaces provide sites for the attachment of important laryngeal muscles and ligaments.

Ligaments attach the inferior surface of the cricoid cartilage to the first cartilage of the trachea.

The superior surface of the cricoid cartilage articulates with the small paired arytenoid cartilages.

The Epiglottis

The shoehorn-shaped epiglottis projects superior to the glottis

The epiglottic cartilage that supports it has ligamentous attachments to the anterior and superior borders of the thyroid cartilage and the hyoid bone.

During swallowing, the larynx is elevated, and the epiglottis folds back over the glottis, preventing the entry of liquids or solid food into the respiratory passageways.

Paired Laryngeal Cartilages

The larynx also contains three pairs of smaller cartilages:

the arytenoid,

corniculate,

and cuneiform cartilages.

The arytenoids and corniculates are hyaline cartilages;

the cuneiforms are elastic cartilages.

The Three Paired Cartilages

• The arytenoid "ladle-shaped” cartilages articulate with the superior border of the enlarged portion of the cricoid cartilage.

• The corniculate “horn-shaped”) cartilages articulate with the arytenoid cartilages.

• The corniculate and arytenoid cartilages play a role in the opening and closing of the glottis and the production of sound.

• Elongate, curving cuneiform “wedge-shaped”) cartilages lie within the aryepiglottic fold that extends between the lateral aspect of each arytenoid cartilage and the epiglottis.

Laryngeal Ligaments• A series of intrinsic ligaments binds all nine

cartilages together to form the larynx.• Extrinsic ligaments attach the thyroid cartilage to

the hyoid bone and the cricoid cartilage to the trachea.

• The vestibular ligaments and the vocal ligaments extend between the thyroid cartilage and the arytenoids.

• The vestibular and vocal ligaments are covered by folds of laryngeal epithelium that project into the glottis.

• The vestibular ligaments lie within the superior pair of folds, known as the vestibular folds.

The vestibular folds, which are relatively inelastic, help prevent foreign objects from entering the glottis and provide protection for the more delicate vocal folds.

The vocal folds are highly elastic, because the vocal ligament is a band of elastic tissue.

The vocal folds are involved with the production of sounds, and for this reason they are known as the true vocal cords.

Because the vestibular folds play no part in sound production, they are often called the false vocal cords.

Laryngeal Ligaments (continue)

Sound Production• Air passing through the glottis vibrates the vocal folds and

produces sound waves. • The pitch of the sound produced depends on the diameter,

length, and tension in the vocal folds. • The diameter and length are directly related to the size of the

larynx.

• The tension is controlled by the contraction of voluntary muscles that change the relative positions of the thyroid and arytenoid cartilages.

• When the distance increases, the vocal folds tense and the pitch rises; when the distance decreases, the vocal folds relax and the pitch falls.

• Children have slender, short vocal folds, and their voices tend to be high-pitched.

• At puberty the larynx of a male enlarges considerably more than that of a female.

• The true vocal cords of an adult male are thicker and longer, and they produce lower tones than those of an adult female.

• The entire larynx is involved in sound production because its walls vibrate, creating a composite sound.

• Amplification and echoing of the sound occur within the pharynx, the oral cavity, the nasal cavity, and the paranasalsinuses.

• The final production of distinct sounds depends on voluntary movements of the tongue, lips, and cheeks.

Sound Production (continue)

The Laryngeal Musculature • The larynx is associated with two different groups of muscles, the intrinsic laryngeal muscles. the extrinsic laryngeal muscles.

The intrinsic laryngeal muscles have two major functions:

One group regulates tension in the vocal folds, while a second set opens and closes the glottis. Those involved with the vocal folds insert upon the thyroid,

arytenoid, and corniculate cartilages.

Opening or closing the glottis involves rotational movements of the arytenoids that move the vocal folds apart or together.

Part of oblique arytenoid muscle: an inconstant fascicle of the oblique arytenoid muscle, originating from the apex of the arytenoid cartilage and inserting to the lateral margin of the epiglottis.

• During swallowing, both extrinsic and intrinsic muscles cooperate to prevent food or drink from entering the glottis.

• Before you swallow, the material is crushed and chewed into a pasty mass known as a bolus.

• Extrinsic muscles then elevate the larynx, bending the epiglottis over the entrance to the glottis, so that the bolus can glide across the epiglottis, rather than falling into the larynx.

• While this movement is under way, intrinsic muscles close the glottis.

• Should any food particles or liquids touch the surfaces of the vestibular or vocal folds, the coughing reflex will be triggered.

• Coughing usually prevents the material from entering the glottis.

Extrinsic Laryngeal muscles

• The extrinsic laryngeal musculature positions and stabilizes the larynx.

• Three of the four strap muscles of the neck, the omohyoid, sternohyoid and thyrohyoid,find attachment to it, only the sternothyroid failing to gain it.

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Lymph Drainage (skip)

• The vocal cords themselves act as a complete barrier separating the two lymphatic areas, but posteriorly there is free communication between them.

• Above the vocal cords, some lymphatics passing via

small nodes lying on the thyrohyoid membrane.

• Below the vocal cords, drainage partially via nodes on the front of the larynx and trachea.

External view of the larynx: (a) anterior aspect; (b) anterolateral aspect.

Nerve supply

• The nerve supply of the larynx is of great practical importance and comprises the superior and recurrent laryngeal branches of the vagus nerve (X).

• The superior laryngeal nerve passes deep to the internal and external carotid arteries where it divides;

• its internal branch pierces the thyrohyoid membrane together with the superior laryngeal vessels to supply the mucosa of the larynx down to the vocal cords.

• The external branch passes deep to the superior thyroid artery to supply the cricothyroid muscle.

• The right arises from the vagus as this crosses the front of the subclavian artery, passes deep to and behind this vessel, then ascends behind the common carotid to lie in the Tracheo-oesophageal grooveaccompanied by the inferior laryngeal vessels.

• The nerve then passes deep to the inferior constrictor muscle of the pharynx to enter the larynx behind the cricothyroid articulation.

The recurrent laryngeal nerve has a different course on each side.

• The left nerve arises on the arch of the aorta, winds

below it, deep to the ligamentum arteriosum, and ascends to the trachea. It then lies in the tracheo-oesophageal groove and is distributed as on the right side.

• The recurrent nerves supply all the intrinsic laryngeal muscles, apart from the cricothyroid, (supplied by the superior laryngeal nerve), and the mucosa below the vocal cords.

The recurrent laryngeal nerve has a different course on each side.

Giraffes are silent animals, but, they are certainly not mute. Sounds like the bleating of calves, and the bellowing of cows, have been heard.