Anatomy of the Larynx Flashcards
3 main functions of larynx?
voice stimulation sphincter of respiratory tract - regulates airflow - protection of aspirated objects conduit for air
what does the larynx consist of?
series of cartilages joined by connective tissue and moved by muscle
located between the pharynx and trachea
where is the larynx located?
in the visceral layer of the pretracheal fascia of the neck
what is enclosed in the pretracheal fascia?
strap muscles thyroid gland trachea and larynx oesophagus and pharynx recurrent laryngeal nerves
what are the strap muscles?
very thing muscular layer which lies anteriorly to the visceral layer of the pretracheal fascia function as accessory muscles of breathing
4 layers of fascia in the neck?
investing fascia = encloses everything
prevertebral fascia = surrounds vertebrae and paravertebral muscles
carotid sheaths = surrounds carotid arteries and veins either side of midline
pretracheal fascia = surrounds midline structres
what structures lie around the larynx?
anterior to the laryngopharynx
between the carotid sheath structures
between C4 and C6 vertebrae
at what level is the hyoid bone found?
C3
cricoid cartilage is found at what level?
C6
also beginning of oesophagus
at what level is the top of the thyroid palpated?
C4/5
how is the larynx involved in aspiration?
raising of the larynx towards the oesophagus reduces the chance of aspiration
if aspiration does occur, then the cough reflex engages
what is the function of cartilage in the upper resp tract?
maintains patency
allows movement
what does the larynx consist of?
skeleton of cartilages suspended from hyoid bone
3 functions of larynx?
maintains patency
cartilage prevents entry of foreign body
vocal cords and cough reflex
produces sound
features of laryngeal cartilages?
diagram
only 1 area of cartilage in the larynx/trachea is a complete ring, what is this?
cricoid cartilage
2 main joints in the movement of the larynx?
cricothyroid joint
cricoarytenoid joint
the epiglottis is what type of cartilage and why?
elastic
moves down to cover larynx to allow food to pass into the oesophagus
4 important cartilages in the larynx?
epiglottis
thyroid
arytenoid
cricoid
how can cricoid pressure be used?
allows blockage of oesophagus in emergency situation to prevent aspiration of gastric contents
press in the cricoid cartilage
lamina of the cricoid cartilage compresses the oesophagus by pressing it against C6 vertebra
oesophagus is closed by the airway is open so ventilation is uninhibited
features of larynx?
laryngeal vestibule = most superior false vocal cord (vestibular fold) laryngeal ventricle true vocal fold infra-glottic cavity
what are vocal cords and what 2 pairs are present in the larynx?
free borders of mucosa covered connective tissue in the larynx
true vocal cords
- vocal process of arytenoid cartilage to thyroid cartilage, movement impacts sound
false vocal cords
- arytenoid cartilage to epiglottis
during laryngoscopy, where is the laryngoscope inserted?
into the vallecula (space between epiglottis and tongue)
what is seen on laryngoscopy?
epiglottis
outer line = false vocal cord
inner line = true vocal cord
space between right/left vocal cords = rima glottidis
what is the aryepiglottic fold?
superior border of quadrangular membrane
what type of muscle are the intrinsic muscles of the larynx and what do they do?
skeletal muscle cause movement of vocal cords - tension = increased pitch - relaxation = decreased pitch - adduction = quieter - abduction = louder
what nerve innervates intrinsic muscles of the larynx?
CN X (vagus)
which intrinsic larynx muscles are tensors and what do they do?
cricothyroid muscles
- tense vocal ligament causing increased pitch
- nods thyroid cartilage
- attaches between anterolateral cricoid cartilage to inferior horn of thyroid cartilage
what are the relaxor muscles of the larynx?
thyroarytenoid muscles
- relax vocal ligament decreasing the pitch
- attaches between posterior thyroid and anterior arytenoid cartilage
what are the first adductor muscles of the larynx and what do they do?
lateral crico-arytenoid muscles
- adduct/bring vocal ligaments together making voice quieter
- attaches between muscular process of arytenoid to anterior cricoid cartilage
what are the second adductor muscles of the larynx and what do they do?
arytenoid muscles
- adducts/brings vocal ligaments together making voice quieter by closing rima glottidis
- attaches between arytenoid cartilages
what are the abductor muscles of the larynx and what do they do?
posterior crico-arytenoid muscles
- abducts vocal cords making voice louder by opening rima glottides
- attaches between posterior cricoid cartilage to muscular process of arytenoid cartilage
how does shape of rima glottides relate to type of speech?
laryngeal muscles relaxed = slightly open = normal respiration
contraction of posterior crico-arytenoids = wide open = forced respiration
contraction of arytenoids = completely closed = phonation
contraction of lateral crico-arytenoids = slightly open only at posterior end = whispering
how may a supra-glottides tumour spread?
drain to superior deep cervical nodes
how may glottic tumours spread?
present on the cords
95% stay on the cords
presents with voice change/airway obstruction
how may a sub-glottic tumour spread?
spread to paratracheal nodes
presents with voice/airway obstruction
how does controlled expiration occur?
contraction of anterolateral abdominal wall and inspiratory intercostal muscles
this helps build pressure in the respiratory tree inferior to the larynx (subglottal pressure)
pressure required depends on vocal task
how does phonation (speech) occur?
once subglottal pressure threshold is reached then air crosses vocal cords causing vibration
length/tension of vocal cords dictates pitch of sound produced by vibration of cords
degree of opening and the shape of the rima glottides also important
what gives resonance to the voice?
larynx is insufficient to produce loud sound
laryngeal buzz is amplified by the pharynx, oral and nasal cavities
funnel shaped pathway from larynx to mouth
how are oral sounds produced?
soft palate tenses (CN V3) and elevates (CN X) to close off entrance into nasopharynx
directs stream of air through the oral cavity
sound is interrupted by the tongue (CN XII) and the teeth/lips (CN VII) to produce most vowels and consonants in English language
how are nasal sounds produced?
soft palate tenses (CN V3) and descends (CN X) to close off entrance into oropharynx
directs stream of air through nasal cavity
produces one of three sounds “m”, “n”, or “ing” depending on position of tonge (CN XII), teeth and lips (CN VII)
through what 3 alternative methods can speech be obtained if larynx is removed?
tracheo-oesophageal puncture
oesophageal speech (suck air into oesophagus and belching the sound)
electrolarynx
what nerve innervates the intrinsic muscles of the larynx (apart from the cricothyroid muscles)
inferior laryngeal nerve
what nerve innervates the cricothyroid muscle
external laryngeal nerve
what innervates the mucosa of the larynx?
above the vocal folds = internal laryngeal nerve
below the folds = inferior laryngeal nerve
where does the inferior laryngeal nerve arise?
left recurrent laryngeal nerve becomes the inferior laryngeal nerve at the level of the cricothyroid joint
what is galen’s anastomosis?
anastomosis between internal and inferior laryngeal nerves
around level of thyroid cartilage
