The larynx is an inferior continuation of the oropharynx. It extends from the epiglottis (namely the glossoepiglottic and pharyngoepiglottic folds) to the inferior aspect of the cricoid cartilage. Inferiorly, it continues as the cervical trachea. The larynx also forms part of the upper respiratory tract.
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Gross anatomy
The larynx consists of a cartilage "skeleton", as well as internal structures that are divided into three subsites, mainly for the purposes of laryngeal cancer staging:
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supraglottis: extends from the tip of the epiglottis to the laryngeal ventricle
epiglottis: divided into suprahyoid and infrahyoid portions
subglottis: extends from the inferior surface of the true vocal cords to the inferior aspect of the cricoid cartilage
Relations
anterior: strap muscles, anterior jugular vein
posterior: esophagus, laryngopharynx
superior: hyoid bone, laryngopharynx
inferior: trachea
Arterial supply
above the vocal cords: superior laryngeal artery (branch of the superior thyroid artery)
below the vocal cords: inferior laryngeal artery (branch of the inferior thyroid artery)
Venous drainage
above the vocal cords: superior laryngeal vein accompanies its artery and drains into the superior thyroid vein (a tributary to the internal jugular vein)
below the vocal cords: inferior laryngeal vein accompanies its artery and drains into the inferior thyroid vein (a direct tributary to the brachiocephalic vein)
Lymphatic drainage
supraglottic: the supraglottic lymphatic network follows the superior laryngeal artery, piercing the thyrohyoid membrane and then draining into the superior deep cervical nodes and the pre-epiglottic nodes 6.
subglottic: the infraglottic lymphatic network drains to the inferior deep cervical nodes, following the inferior laryngeal artery, and/or the prelaryngeal (Delphian) nodes via the conus elasticus (aka the lateral cricothyroid ligaments) 6.
Both the superior and inferior deep cervical nodes then drain into the right and left jugular trunks, which subsequently empty into the right lymphatic duct and the thoracic duct on the left.
Muscles of the larynx
There are two board groups of muscles that act on the larynx as a whole or individual components of the larynx:
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extrinsic muscles of the larynx move the position of the entire larynx and are subdivided into the:
infrahyoid muscles which depress the hyoid and larynx, and the
suprahyoid muscles, along with stylopharyngeus (a pharyngeal muscle), which elevate the hyoid and larynx.
intrinsic muscles of the larynx which either control the inlet of the larynx and move the vocal ligaments
Innervation
motor: the recurrent laryngeal nerve supplies all the intrinsic muscles of the larynx apart from the cricothyroid muscle, which is supplied by the external laryngeal nerve
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sensory:
above the vocal cords (supraglottic): internal laryngeal nerve (branch of the superior laryngeal nerve)
below the vocal cords (infraglottic): recurrent laryngeal nerve
Development
the larynx is formed from the laryngotracheal groove, which is related to the caudal aspect of the floor of the primordial pharynx
the cartilages of the larynx develop from the 4th and 6th pharyngeal arches
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