The larynx Flashcards
What is the larynx?
Part of the respiratory tract which is reinforced with cartilages which articulate with each other at synovial joints and can be moved with precision
What are the functions of the larynx?
- protection of the lower respiratory tract to prevent inhalation of food or liquids during swallowing or vomiting
- phonation by vibration of vocal folds
What are the key structures in the laryngeal skeleton?
- hyoid bone
- thyroid cartilage
- cricoid cartilage
- arytenoid cartilages
- epiglottis
What is the epiglottis?
Cartilage which moves over the opening of the larynx to protect the airway
How is the epiglottis connected to the thyroid cartilage?
By the thyroepiglottic ligament
How are the hyoid bone and thyroid cartilage connected?
by the thyrohyoid membrane and thyrohyoid muscle
What are the features of the thyroid cartilage?
- large lamina on both sides
- laryngeal prominence
- open posteriorly
- 2 superior horns (each side) which connect to hyoid by thyrohyoid membrane
- 2 inferior horns (each side) connect to cricoid
What are the features of the cricoid?
- signet in shape
- only complete ring of cartilage in respiratory system
- attached to thyroid by cricothyroid joint
- articulates with cricoid cartilage
Where are the arytenoids?
on top of the cricoid
What are the cricoarytenoid joints?
synovial joints between the arytenoids and the cricoid lamina
Where do the vocal folds attach?
- anteriorly to thyroid cartilage
- posteriorly to the vocal processes of the arytenoids
What movements are possible at each cricoarytenoid joint?
- sliding apart/together
- rotation about a vertical axis
- tilting forwards or backwards
What are the effects of the sliding motion of the arytenoids?
- slide medially = adduction (close) of vocal cords
- slide laterally = abduction (open) of vocal folds
What are the effects of the rotation movement of the arytenoids?
- rotate inwards = adduction (close) of vocal folds
- rotation outwards = abduction (open) of vocal folds
What are the effects of the tilting movement of the arytenoids?
- tilting backwards = inc length and tension, dec thickness
- tilting forwards = dec length and tension, inc thickness
What is the action of the cricothyroid muscle?
- pulls thyroid cartilage forward and down
- move cricoid carilage up (so arytenoids move back)
- stretch vocal cords, making them thinner, and increasing pitch
What innervates the cricothyroid muscle?
superior laryngeal nerve - branch of CNX vagus
Where is the posterior cricoarytenoid muscle?
extends from the muscular process of the arytenoid to the posterior lamina of the cricoid cartilage
What is the action of the posterior cricoarytenoid muscle?
rotates the arytenoids outwards to abduct the vocal folds and open the rima glottis - these are the only abductors of the vocal folds
Where are the lateral cricoaryntenoid muscles?
extend between muscular process of arytenoid to superior/anterior areas of the cricoid
What is the action of the lateral cricoarytenoid muscles?
rotates the arytenoids inwards to adduct the vocal folds and close the rima glottis
Where are the interarytenoid muscles?
Extend between the arytenoids both laterally and oblique
What is the action of the interarytenoid muscles?
adduct the vocal folds
What is the thyroarytenoid muscle?
a broad muscle running from teh arytenoid to the thyroid cartilage
What is the action of the thyroarytenoid muscle?
pulls the arytenoids closer to the thyroid cartilage, making the vocal folds slacker/thicker/looser for lower pitch, making broad adjustments
What is the vocalis muscle?
the inner portion of the thyroarytenoid muscle which makes finer adjustments to the thickness of the vocal folds/pitch
What are the vestibular folds?
- ‘false vocal cords’
- superior to vocal folds
- respiratory epithelium (different mucosa to vocal folds)
- no role in phonation
What are the mucosas of the larynx?
- larynx = lined with respiratory epithelium
- vocal folds = lined with stratified squamous epithelium
What are the branches of the vagus nerve used in the larynx?
- superior laryngeal nerve
- recurrent laryngeal nerve
What does the superior laryngeal nerve innervate?
- sensory to mucosa of larynx
- motor to cricothyroid muscles
What does the recurrent laryngeal nerve innervate?
motor to all laryngeal muscles except cricothyroid
What results from damage to superior laryngeal nerve?
- loss of sensation to larynx = no cough reflex/swallow initiation -> aspiration
- loss of motor to cricothyroid muscle - difficulty regulating pitch
What results from damage to recurrent laryngeal nerve?
- all muscles affected on paralysed side except cricothyroid and interarytenoids
- because the interarytenoids still work - partially adducted so harsh raspy voice
What can cause damage to recurrent laryngeal nerve?
usually unilateral damage from lung pathology (usually left) or thyroid gland operations
