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ANATOMY

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-two openings within airway: nose which leads to nasopharynx and mouth leading to the oropharnyx
-nasopharynx and oropharynx is separated by the palate and eventually join posteriorly to form the pharnyx
-pharynx is a fibromuscular structure that resembles a U shape
-epiglottis functions to help separate the oropharynx and larngopharynx
-during swallowing the epiglottis helps cover the glottic opening to prevent aspiration
-larynx is held together by ligaments and muscle and is the structual component of the airway distal to the pharnyx

larynx is made up of nine cartilages

-thyroid cartilage
-cricoid cartilage
-epiglottic cartilage
-paired arytenoid cartilages
-paired corniculate cartilages
-paired cuneiform cartilages

sensory innervation

-sensory innervation of the upper airway is primarily from cranial nerves: V1, V2, V3, IX, X
V1 (anterior ethmoidal nerve): innervates the mucous membrane of the anterior portion of the nose

V2 ( spenopalatine nerve) : innervates the mucous membrane of the posterior portion of the nose

V3 ( lingual nerve) : innervates the anterior 2/3 of the tongue

CN IX (glossopharyngeal n.) : innervates the posterior 1/3 of the tongue, roof of the pharnyx, tonsils, and soft palate undersurface

CN X (vagus nerve) : innervates the airway below the epiglottis
divides into 2 branches: Superior laryngeal nerve (which has 2 branches: external and internal branch)
Recurrent laryngeal nerve
Superior laryngeal nerve (SLN): internal branch provides sensory innervation of the larynx between the epiglottis and vocal cords
internal branch provides no motor innervation
internal branch provides nearly all innervation of the larynx except for the anterior glottic opening

external branch provides sensory innervaton of the anterior glottic opening
motor innervation external branch provides motor innervation to the cricothyroid muscle

Recurrent laryngeal nerve (RLN) provides all the motor innervation of the muscles of the larynx except the cricothyroid muscle
provides sensory innervation to the subglottic mucosa and muscle spindles within the larynx

Damage of the motor nerves innervating the larynx:
-unilateral denervation of the SLN: clinical findings are subtle
-bilateral denervation of the SLN: hoarsness and perhaps easy tiring of the voice although the airway is not in jeopardy
-unilateral denervation of the RLN: ipsilateral vocal cord paralysis therefore the quality of voice is diminished
-bilateral denervation of the RLN: if acute: may result in stridor and perhaps respiratory distress (flacid closure of vocal cords)
if chronic: less frequent airway problems secondary to compensation of other muscles

blood supply

-branches of the carotid arteries
-thyroid artery
-cricothyroid artery which branches from superior thyroid cartery