10. Functional Anatomy Of The Larynx Flashcards
What are the functions of the larynx?
Airway protection
Ventilation
Cough reflex
Production of sound (phonation)
Where does the larynx start and end?
Begins at laryngeal inlet and ends at lower border of cricoid cartilage (C6)
What does the larynx lie below?
Hyoid bone
What are the cartilages that form the framework of the larynx?
Thyroid cartilage
Cricoid cartilage
Arytenoid cartilages
Epiglottis
Which membranes are prt of the framework of the larynx?
Thyrohyoid membrane
Cricotracheal membrane
Cricothyroid membrane
What are the Aryepiglottic folds formed from?
Quadrangular membrane
What gives shape to the true vocal cord?
Free upper border of cricothyroid membrane
What gives shape to false vocal cord?
Free lower border of quadrangular membrane
What internally divides the larynx?
Mucosal folds
What are the 3 regions of the larynx?
Supraglottis
Glottis
Infraglottis
What is the supraglottis?
Laryngeal vestibule - include false cords
What type of epithelium lines the larynx except the true vocal cords?
Pseudostratified ciliated columnar epithelium
What type of epithelium lines the true vocal cords?
Stratified squamous epithelium
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What is the gap between the true vocal cords called?
Rima glottidis
When do vocal cords need to be viewed?
Intubation - placement of an endotracheal tube into subglottic region
Flexible nasoendoscopy
What is the vallecula?
Recess between tongue and epiglottis where laryngoscope is placed during intubation
What do the 2 main actions of the intrinsic laryngeal muscles alter?
Size/shape of laryngeal inlet
Tension/position of vocal cords
What are the actions of the intrinsic laryngeal muscles?
Swallowing - close laryngeal inlet and vocal cords, protect respiratory tract
Inspiration and expiration - open vocal cords, allowing movement of air
Phonation and cough reflex - partially closed vocal cords
Which intrinsic muscle of the larynx acts to open the vocal cords?
Posterior cricoarytenoid
What does the arytenoids position on cricoid determine?
Position of true vocal cords and therefore size of aperture
What are the intrinsic muscles innervated by except cricothyroid muscle?
Recurrent laryngeal nerve of vagus (2 - one for each side)
What is the cricothyroid muscle innervated by?
External branch of superior laryngeal nerve
What is the position of the vocal cords in phonation?
Closely adduct, with small gap for vibrations from expired air forced out
What happens in the cough reflex?
Inspire and fill lungs with air Vocal cords then adducted Expiration muscles contract Intrathoracic pressure builds Then cords suddenly abducted Explosive outflow of air
Which muscle is involved in controlling tension of vocal cords?
Bilateral contraction of cricothyroid muscles increases tension
How does the cricothyroid muscle increase tension in vocal cords?
Tilts thyroid cartilage forward on cricoid, increasing tension in vocal cords
Important for reaching higher pitch
Why can thyroid surgery sometimes result in hoarseness of voice, especially in high pitched sounds?
Cricoid muscle innervated by external branch of superior laryngeal nerve
This nerve is closely related to superior thyroid artery, and can therefore be damaged in thyroid surgery
This can result in hoarseness of voice
What happens to the larynx during swallowing?
Hyoid bone elevated and moved anteriorly by suprahyoid muscles - larynx moves up and forward
Tongue pushes epiglottis posterior lay and aryepiglottic muscles contract
Closure of vocal cords
What are the branches of the superior laryngeal nerve?
Internal - supraglottic (sensory)
External - cricothyroid (motor)
Describe the path of the recurrent laryngeal nerve to the larynx
Arises distally from vagus
Passes anteriorly to the loops under right subclavian artery and on left, the arch of aorta
Ascends in tracheo-oesophageal groove
Close anatomical relationship with thyroid gland and inferior thyroid arteries
What can cause injury to recurrent laryngeal nerve?
Thyroid surgery
Aortic arch aneurysm
Cancer involving apex of lung
Disease or surgery involving larynx, oesophagus or thyroid
What do unilateral RLN lesions lead to?
Unilateral vocal cord palsies - hoarse voice, ineffective cough
What position do paralysed vocal cord assume?
Paramecium position
Between fully abducted and fully adducted
What happens in bilateral RLN injuries?
Both vocal cords paralysed and in paramedian position
Narrow glottis
Significant airway obstruction - emergency surgical airway
