anatomy of larynx

LarynxLarynxLarynxLarynx

Larynx

• is a hollow muscular ligament structure with cartilagenous framework.• Its cavity continuous below with the trachea, and above opens into the pharynx.• is a valve (or sphincter) to close the lower respiratory tract (protection)• and an instrument to produce sound.(phonation)

• Respiration• Deglutition

• Extent • Root of tongue – trachea • Front of 3,4,5,6 cervical vertebrae

Larynx

• Three large unpaired cartilages (cricoid, thyroid, and epiglottis)

• Three pairs of smaller cartilages (arythenoid, corniculate, and cuneiform)

• A fibroelastic membrane and numerous intrinsic muscles

Epiglottis• is a leaf-shaped cartilage.• is attached by its stem to the

posterior aspect of the thyroid cartilage by thyro-epiglottic ligament.

• projects posterosuperiorly.• Its upper margin is behind the

pharyngeal part of the tongue.• Its inferior half of the posterior

surface of the epiglottis is raised slightly to form an epiglottic tubercle.

Thyroid cartilage

• is the largest of the laryngeal cartilages.

• is formed by joining of a right and a left lamina anteriorly as the laryngeal prominence (A’dam’s apple ).

• are widely separated posteriorly.

Thyroid cartilage

• The angle between the two laminae is more acute in men (90 C) than in women (120 C) so the laryngeal prominence is more apparent in men than women.

Cricoid cartilage

• is inferior of the laryngeal cartilage and completely encircles the airway.

• is shaped like a ‘signet ring’ with a broad lamina of cricoid cartilage.

• C6• Foundation stone

Arytenoid cartilage

•are pyramidal-shaped cartilages.

Surface of Arytenoid cartilarges

• Base is concave and articulates with the sloping articular facet on the lamina of cricoid cartilarge.

• Apex articulates with a corniculate cartilage.

• Medial surface of each cartilage faces the other.

• Anterolateral surface has two depressions for muscle (vocalis) and ligament (vestibular ligament) attachment.

• Elongated Anterior angle is vocalis process for the vocal ligament attachment.

• Lateral angle is muscular process for attachment of the posterior and lateral crico-arythenoid muscles.

Base of Arytenoid Cartilarges

• Corniculate cartilages articulate with the apices of the arytenoid cartilage.

• Corniculate apices project posteromedially towards each other.

• Cuneiforms are suspend in the part of the fibroelastic membrane-aryepiglottic membrane.

• Thyroid, cricoid and basal parts of arytenoid are composed of hyaline cartilage – ossify after 25

• Apex of arytenoid and all other are elastic cartilage

Laryngeal Joint; Crico-thyroid Joint

• Synovial joint• Compose of1. Crico-thyroid joint2. Crico-arytenoid joint • The cricothyroid joints

enable the thyroid cartilage to move forward and tilt downwards on the cricoid cartilage (effectively lengthens and puts tension on the vocal ligaments).

• between the cricoid cartilage and of the arytenoid cartilages.

• enable the arythenoid cartilages to slide away or towards each other and to rotate so that

• The vocal process pivot either towards or away from the midline (abduct and adduct the vocal ligament).

Laryngeal Joint; Crico-aretynoid Joint

• Thyrohyoid membrane• Hyo-epiglottic ligament• Cricotracheal ligament

Extrinsic ligamentIntrinsic ligament

• upper quadrangular ligament• Cricothyroid ligament (cricovocal and cricothyroid membrane)

Cricothyroid ligament• is attached to the arch of

cricoid cartilage and extends superiorly.

• Thyroid cartilage anteriorly and vocal process posteriorly.

• The free margin of this ligament is thickened to form the vocal ligament, which is under the vocal fold (true ‘vocal cord’) of the larynx.

• is also thickened anteriorly in the midline to form a distinct median cricothyroid ligament.

Quadrangular Membrane

• Run between the lateral margin of the anterolateral surface of the arytenoid cartilage on the same side to epiglottis superiorly

• Its free lower margin is thickened to form the vestibular ligament under the vestibular fold (false ‘vocal cord’).

Vestibular Ligament

• Vestibular ligament is attached posteriorly to the arytenoid cartilage and anteriorly to the thyroid angle just superior to the attachment of the vocal ligament.

Cavity of the larynx• is tubular in shape.• is lined by the mucosa.• opens superiorly (laryngeal inlet) into the

anterior aspect of the pharynx just below and posterior to the tongue.

• opens inferiorly into the lumen of trachea.• Laryngeal inlet can be closed by downward

movement of epiglottis whereas the inferior opening is continuously open.

• Wall of laryngeal cavity: Lateral wall: aryepiglottic folds. Anterior border: mucosa covering the superior

margin of the epiglottis. Posterior border: interarytenoid notch (between

the two corniculate tubercles).

Three Division of Laryngeal Cavity

• Two pairs of mucosal fold (vestibular and vocal folds) divide the cavity into three major regions;

1. Vestibule is (upper chamber) between the laryngeal inlet and the vestibular ligament.

2. (Laryngeal) Ventricle (middle chamber) is between the vestibular folds above and the vocal folds below.

3. Infraglottic space (inferior chamber) is between the vocal folds and the inferior opening of the larynx.

Laryngeal Ventricles and Saccules

• produce an expanded trough-shaped space.

• Larygeal saccule is an elongate tubular extension of each ventricle projects anterosuperior between the vestibular fold and thyroid cartilage.

• Within the walls of the saccule are numerous mucous glands which secrete the mucus to lubricate the vocal folds.

Rima Vestibuli• is a triangular-shaped

opening.• is between the two

adjacent vestibular folds at the entrance to the middle chamber of the laryngeal cavity.

• Its apex is anterior.• Its base is formed by

the posterior wall of the laryngeal cavity.

Rima Glottidis

• is between the two adjacent vocal folds.

• separates the middle chamber above from the infraglottic cavity below.

• It base is formed by the fold of mucosa (inter-arytenoid fold) at the bottom of the inter-arytenoid notch.

Both the rima glottidis and the rima vestibuli can be opened and closed by movement of the arytenoid cartilages and associated fibro-elastic membrane.

Function of Intrinsic Muscles

• adjust tension in the vocal ligaments.

• open and close the rima glottidis.• control the inner dimensions of the

vestribule.• close the rima vestibuli.• facilitate closing of the laryngeal

inlet.

Action of Intrinsic Muscles

• Acting on the cricothyroid and crico-arytenoid joints.

• Adjusting the distance between the epiglottis and arytenoid cartilage.

• Pulling directly on the vocal ligament.• Forcing soft tissues associated with the

quadrangular membranes and vestibular ligaments toward the midline.

Cricothyroid Muscles• are fan-shaped muscles.• are attached to the arch of the cricoid

cartilage and attach to the thyroid cartilage.

• have two parts; oblique and straight.• Oblique part runs in a posterior

direction from the arch of the cricoid cartilage to the inferior horn of the thyroid cartilage.

• Straight part runs more vertically from the arch of the cricoid cartilage to the posteroinferior margin of the thyroid lamina.

• move the cricothyriod joints.• pull the thyroid cartilage forward and rotate it

down relative to the cricoid cartilage-lengthen the vocal folds.

• are the only one intrinsic (lies outside) muscles innervated by the superior laryngeal branches of the vagus nerve (CN X).

• All other intrinsic muscles are innervated by the recurrent laryngeal branches of the vagus nerves.

Cricothyroid Muscles

Posterior crico-arytenoid muscle

• originate from shallow depression on the posterior surface of the lamina of cricoid cartilage.

• run superolaterally to converge on the muscular processes of the arytenoid cartilage.

• abduction and externally rotate the arytenoid cartilage to open the rima glottidis.

• are innervated by recurent laryngeal branches of the vagus nerve (CN X).

Lateral Crico-arytenoid Muscles

• originates from the upper surface of the arch of the cricoid cartilage.

• runs posterosuperiorly to insert on the muscular process of the arytenoid cartilage.

• adduct and internally rotate the arytenoid cartilage- adducted vocal folds with an open air channel posteriorly between adjacent arytenoid cartilages.

• are innervated by the recurrent laryngeal branches of the vagus nerve (CN X).

Transverse arytenoid m.

• is a single muscle.• spans the distance

between adjacent lateral margins of the arytenoid cartilages and covers the posterior surfaces of these cartilages.

• is innervated by the recurrent laryngeal branches of the vagus nerve (CN X).

Oblique arytenoid muscles

• are pair muscles.• run from the posterior surface of

the muscular process of one arytenoid cartilage to the apex of the arytenoid cartilage on the other side.

• Some fibers of this muscle continue laterally around the margin of the arytenoid cartilage and into the aryepiglottic fold to continue as part of aryepiglottic muscle.

• can narrow the laryngeal inlet by constricting the distance between the arytenoid cartilage and the epiglottis.

• is innervated by the recurrent laryngeal branches of the vagus nerve (CN X)

Vocalis• are elongate muscles lateral to

and running parallel with each vocal ligament.

• attaches posteriorly to the lateral surface of the vocal process and adjacent depression on the anterolateral surface of the arytenoid cartilage.

• insert anteriorly along the length of the vacal ligament to the thyroid angle.

• adjust tension in the vocal folds.• are innervated by the recurrent

laryngeal branches of the vagus nerve (CN X).

Thyro-arytenoid Muscles

• are broad flat muscles lateral to the fibro-elastic membrane of the larynx and the laryngeal ventricles and saccules.

• run from a vertical line of origin on the lower half of the thyroid angle and adjacent external surface of the cricothyroid cartilage.

• Some of the fibers may continue into the aryepiglottic fold and reach part of thyro-epiglottic muscle.

Function of the Larynx

• is an elaborate sphincter for the lower respiratory tract.

• provides a mechanism for producing sounds.

• adjusts the size of the ventricle cavity result from changes in the dimensions of the rima glottidis, rima vestibuli, vestibule, and the laryngeal inlet.

• This changes result from the muscle actions and laryngeal mechanics.

During Quiet Respiration

• The laryngeal inlet, vestibule, rima vestibule and rima glottidis are open.

• The arytenoid cartilages are abducted.

• The rima glottidis in triangular shaped.

During Force Respiration

• The arytenoid cartilage are rotated laterally, mainly by action of the posterior crico-arytenoid m.

• As a result, the vocal folds are abducted, and the rima glottidis widens into a rhomboid shape, which effectively increases the diameter of the laryngeal airway.

Phonation• Arytenoid cartilages and

vocal folds are adducted and air is forced through the closed rima glottidis.

• This action causes the vocal folds to vibrate against each other and produce sounds, which can then be modified by the upper parts of the airway and oral cavity.

• Tension in the vocal folds can be adjusted by the vocalis and cricothyroid muscle.

Effort Closure

• occurs when air is retaind in the thoracic cavity to stablize the trunk, for example during heavy lifting, or as part of the mechanism for increasing intra-abdominal pressure.

• During effort closure, the rima glottidis is completely closed, as is the rima vestibuli and lower parts of the vestibule.

• The result is to completely and forcefully shut the airway.

During Swallowing• The rima glottidis, the rema vestibuli, and vestibule are

closed and the laryngeal inlet is narowed.• The larynx is move upward and forward causes the

epiglottis to swing downward towards the aryngeal inlet (also facilitate closing the laryngeal inlet and opening the esophagus).

• All these actions together prevent solids and liquids from entry into the airway and facilitate their movement through the piriform fossae into the esopahgus.

Tracheostomy

• is a procedure in which a hole is made in the trachea and a tube is inserted to enable ventilation when the foreign body obstruct to the larynx.

• A small transverse incision is placed in the lower third of the neck anteriorly (at level 2nd and 3rd tracheal rings), deviates the strap muscle laterally and divides the isthmus of the thyroid gland.

• Pateint with long-term tracheostomies are unable to vocalize because no air is passing through the vocal cords.

Arterial Supply• Superior laryngeal a.

originates from the superior thyroid a. and accompaneis the internal branch of the superior laryngeal nerve through the thyrohyoid membrane.

• Inferior laryngeal a. originates from the inferior thyroid branch of thyrocerical trunk, together with the recurrent laryngeal n.

Veins draining the larynx

• Superior laryngeal veins drain into superior thyroid veins, which in turn drain into the internal jugular vein.

• Inferior laryngeal veins drain into inferior thyroid veins, which drain into the left brachiocephalic veins.

Lymphatics

• drain regions above and below the vocal folds:• Those above the vocal fold follow the superior

laryngeal a. and terminate in deep cervical nodes associated with the bifurcation of the common carotid a.

• Those below the vocal folds drain into deep nodes associated with the inferior thyroid a. or with nodes associated with the front of the cricothyroid ligament or upper trachea.

Nerves

• Sensory and motor is supplied by 2 branches of vagus nerve:

1. Superior laryngeal nerve

2. Recurrent laryngeal nerve

Superior Laryngeal Nerve• Originate from the inferior vagal

ganglia.• Divide into internal and external

branches just above the level of the superior horn of the hyoid bone.

1. External branch (external laryngeal br.) decends along the lateral wall of the pharynx to supply and penetrate the inferior constrictor of the pharynx and ends by the supplying the cricothyroid muscle.

2. Internal branch (internal laryngeal nerve) passes anteroinferiorly to penetrate the thyrohyoid membrane.

(it is mainly sensory and supplies the laryngeal cavity above level of the vocal folds.)

Recurrent Laryngeal Nerves

• Sensory to the laryngeal cavity below the level of the vocal folds.

• Motor to all intrinsic muscles of the larynx except for the cricothyroid.

• Left recurrent laryngeal n. originates in the thorax.

• Right recurrent laryngeal n. originates in the root of neck.

• Enter the larynx deep to the margin of the inferior constrictor.

• Sinus of morgagni [ventricle of larynx]

• Singer’s nodule• Piriform fossa