LARYNX

which tract in the body is the larynx a part of

the larynx is part of the respiratory tract

what is the larynx reinforced by

the larynx is reinforced by cartilage

what is special about the cartilages in the larynx

the cartilages in the larynx articulate with each other

how do the cartilages in the larynx articulate with each other

the cartilages in the larynx articulate with each other at synovial joints

what do the synovial joints allow the laryngeal cartilages to do

the synovial joints allow the laryngeal cartilages to be moved with precision relative to each other

what is the primary function of the larynx

• protect the lower respiratory tract by…

• preventing inhalation of food/ liquids during swallowing/ vomiting

what is the secondary function of the larynx

• generation of noise by vibration of vocal folds (at different frequencies) as air moves past them

• i.e. phonation

what occurs to the laryngeal cartilages during swallowing

the laryngeal cartilages elevate during swallowing

which structures make up the laryngeal skeleton (6)

• hyoid bone

• thyroid cartilage

• cricoid cartilage

• arytenoid cartilage

• corniculate cartilage

• epiglottis

the laryngeal skeleton: hyoid bone

• joined to thyroid cartilage by thyrohyoid membrane

the laryngeal skeleton: thyroid cartilage

• joined to hyoid bone by thyrohyoid membrane

• joined to cricoid cartilage by cricothyroid joint

which two structures is the cricothyroid joint formed by

the inferior horn of the thyroid cartilage and the lateral aspect of the cricoid cartilage

what is the function of the cricothyroid joint

allows the cricoid cartilage to swing up and meet the thyroid cartilage

the laryngeal skeleton: cricoid cartilage

• shaped like a signet ring (flat face of ring faces posteriorly in the larynx)

• the only COMPLETE RING of cartilage in the respiratory system

the laryngeal skeleton: arytenoid cartilage

• the arytenoid cartilages are paired

• the vocal folds attach to the vocal processes of the arytenoids posteriorly and to the thyroid cartilage anteriorly

• the arytenoid cartilages form 2 synovial joints with the cricoid lamina » cricoarytenoid joints

what movements are possible at the cricoarytenoid joints (3)

1. sliding apart (abduction)/ sliding together (adduction)

2. rotation about a vertical axis e.g. inserting a screw from above and twisting it left and right

3. tilting backwards/ tilting forwards

movements at the cricoarytenoid joints: sliding

• sliding medially i.e. adduction » closes vocal folds

• sliding laterally i.e. abduction » opens vocal folds

movements at the cricoarytenoid joints: rotation about a vertical axis

• rotation inwards i.e. adduction » closes vocal folds

• rotation outwards i.e. abduction » opens vocal folds

movements at the cricoarytenoid joints: tilting

• tilting backwards » increases length and tension - decreases thickness

• tilting forwards » decreases length and tension - increases thickness

the laryngeal skeleton: epiglottis

• flap of cartilage

• protects the trachea by folding backwards during swallowing

• prevents food and drink from entering lungs

which cartilage is the Adam’s apple

the thyroid cartilage

what are the laryngeal folds

laryngeal folds are the broad term for the soft tissue folds in the larynx i.e. the vocal folds and the vestibular folds

diagram of vocal and vestibular folds

name this structure

vestibular/ ventricular folds

vertically the larynx is constricted at the _____ _____ by _____ _________

vertically the larynx is constricted at the vocal folds by conus elasticus i.e. the cricothyroid membrane

what type of tissue are the vocal folds/ cords made of

the vocal folds/ cords are made of smooth muscle tissue

another term for vestibular folds

false vocal folds/ cords

how are the vestibular folds specialised

• the vestibular folds contain mucous glands which secrete mucus that lubricate the true vocal folds below

• the vestibular folds have no muscle

which laryngeal folds vibrate

only the true vocal folds vibrate

what type of epithelium is found in the larynx

respiratory epithelium i.e. ciliated pseudostratified columnar epithelium

what structure in the larynx is the exception to being lined with respiratory epithelium

• the vocal folds

• vocal folds are lined with stratified squamous epithelium

why are vocal folds lined with stratified squamous epithelium

because they are constantly in contact (during adduction) and stratified epithelium provides durability

what is the laryngeal inlet

the opening of the larynx

what is the rima glottidis

the opening between the vocal cords

what is the rima glottidis formed by

the rima glottidis is formed by the vocal processes of the arytenoid cartilages and the vocal folds

laryngeal inlet vs rima glottidis

• the laryngeal inlet and the rima glottidis are different regions of the same opening

• the laryngeal inlet is superior to the rima glottidis

when are the vocal folds open and what is the exception

• the vocal folds are usually open

• except during swallowing and speech

what happens to the vocal folds during swallowing and speech

• the vocal folds forcefully adduct during swallowing and speech

• to protect the lower respiratory tract

what happens to the vocal folds during phonation

• the vocal folds adduct

• the tension of the vocal folds change

this causes pitch and volume to vary

name these laryngeal muscles

what is the function of the interarytenoid muscles

• adduct the arytenoid cartilages

• close the vocal folds

what is the function of the posterior cricoarytenoid muscles

• abduct the vocal folds

the posterior cricoarytenoid muscles are the ONLY ABDUCTORS of the vocal folds

name these laryngeal muscles

what is the function of the thyroarytenoid muscles

• rotate the arytenoid cartilages inwards

• adduct/ close the vocal folds during swallowing and shouting to forcibly close the vocal folds

what is the function of the lateral cricoarytenoid muscles

• rotate the arytenoid cartilages inwards

• adduct/ close the vocal folds during swallowing and shouting to forcibly close the vocal folds

name this laryngeal muscle

what is the function of the cricothyroid muscles

• act on the cricothyroid joint to move the cricoid cartilage upwards

• this then moves the arytenoid cartilages backwards

• the tension of vocal folds increase

—

these muscles make the initial adjustments to the tension of the vocal folds

name this laryngeal muscle

vocalis (inner portion of thyroarytenoid)

what is the function of the vocalis muscle

• pulls the arytenoid cartilages forwards towards the thyroid cartilage

• this relaxes the vocal folds

• the vocalis also makes fine adjustments

what happens to the vocal folds during phonation

phonation requires closure of the vocal folds

what is another requirement of vocal folds for phonation

the vocal folds need to be closed and TENSED for phonation

how do the vocal folds open and close

• closure of the vocal folds raises sub-glottal pressure (pressure of air) beneath the vocal folds

• sub-glottal pressure increases until it is greater than the closing force of the muscles holding the vocal folds together

• vocal folds open

• as air rushes past it causes the vocal folds to vibrate

• vocal folds close

cycle repeats

which variable factors in vocal folds affect pitch (3)

• length

• tension

• thickness

how can the three variable factors be altered

• moving the arytenoids backwards » stretching the vocal folds

• moving the arytenoids forwards » relaxing the vocal folds

what does the resting length of vocal folds determine

• the resting length of vocal folds determine habitual pitch

• men > women > children

which nerve innervates the larynx

the vagus nerve/ CN X

which branches of the vagus nerve/ CN X innervate the larynx

• the superior laryngeal nerve

• recurrent laryngeal nerves

both are paired

how do the superior laryngeal nerves innervate the larynx

• internal branches of SLN are sensory to the mucosa of the larynx

• external branches of SLN are motor to the cricothyroid muscles

how do the recurrent laryngeal nerves innervate the larynx

• RLN are motor to all other muscles of the larynx

• (except the cricothyroid)

consequences of damage to the superior laryngeal nerves

loss of sensation to the larynx

• inoperative cough reflex

• inhalation of food into the respiratory tract i.e. silent aspiration

• silent aspiration can lead to pneumonia and death

loss of motor innervation to the cricothyroid muscles

• difficulty in regulating pitch

what is the typical nature of damage to the recurrent laryngeal nerve

damage to the recurrent laryngeal nerve is usually unilateral

causes of damage to the recurrent laryngeal nerves (2)

• lung pathology - particularly the left RLN

• thyroid gland operations - either side of RLN

consequences of damage to the recurrent laryngeal nerves

• all muscles on affected side are paralysed

• except the cricothyroid and interarytenoids

—

• vocal folds will still be tensed as cricothyroid is functional

• interarytenoids cross the midline and are therefore innervated bilaterally i.e. some RLN fibres on right innervate left muscle and vice versa so vocal folds are partially adducted » harsh raspy voice