Structures in the Larynx
Nerves
internal laryngeal – branch of the superior laryngeal of the vagus
- pierces the thyrohyoid membrane and provides sensory innervation of the larynx superior to the vocal cords
external laryngeal – branch of the superior laryngeal of the vagus; supplies cricothyroid muscle (all other intrinsic laryngeal muscles supplied by recurrent laryngeal)
Muscles
posterior cricoarytenoid – back of cricoid cartilage to muscular process of arytenoid
- innervation
: recurrent laryngeal
- action
: opens glottis
lateral cricoarytenoid – upper arch of cricoid to muscular process of arytenoid
- innervation
: recurrent laryngeal
- action
: narrows the glottis
arytenoideus – consists of transverse and oblique arytenoids
- innervation
: recurrent laryngeal
- interarytenoid (transverse arytinoid)
– connects the posterior aspects of the arytenoid cartilages; adducts vocal cords; only unpaired muscle in the larynx
- oblique arytenoid
– run from the posterolateral process of one arytenoid to the superior part of the other; fibers continue to the epiglottis as the aryepiglottic muscles; result is that contraction both closes the vocal cords, and depresses the epiglottis thus closing the trachea in two ways when swallowing
cricothyroid – anterior surface of cricoid to thyroid cartilage
- innervation
: superior laryngeal
- action
: tightens vocal cords
thyroarytenoid – thyroid cartilage to arytenoid cartilage
- innervation
: recurrent laryngeal
- action
: relaxes vocal cords
vocalis – part of thyroarytenoid; slips of muscle go directly to the vocal cords and make fine adjustments
thryroepiglotticus – thyroid cartilage to the epiglottis
- innervation
: recurrent laryngeal
- action
: depresses epiglottis
Joints
cricothyroid – synovial joints between cricoid and inferior horn of thyroid whose movements change length of vocal cords
Ligaments and Membranes
vocal – forms the skeleton of the vocal folds; form the superior margin of the conus elasticus; run from the junction of the laminae of the thyroid cartilage to the vocal processes of the arytenoid cartilages
cricothyroid (conus elasticus) – elastic membrane that connects the cricoid and thyroid cartilages; upper free edge is the vocal ligaments
quadrangular membrane – extends from the arytenoid cartilage to the epiglottis; inferior margin forms the vestibular ligament which is covered by the vestibular fold, constituting the false vocal cords
Miscellaneous
vestibule of the larynx – lies superior to the vestibular folds
ventricle – lies between the true and false vocal cords; blind pouch that contains glands to lubricate the cords
infraglottic cavity – lies inferior to the true cords and continues to the inferior border of the cricoid cartilage
vestibular folds – cover the vestibular ligament; contstitue the false vocal cords
vocal folds – the true vocal cords; overlie the vocal ligaments
cricoid cartilage – the only cartilage to completely encircle the trachea
thyroid cartilage
arytenoid cartilage
epiglottic cartilage – cartilagenous center of the epiglottis
rima glottidis – the narrowing of the pharynx between the vocal folds