Lecture 19- The larynx Flashcards
the pharynx deals wtih a bit of a design flaw…
Air must pass through the nasopharynx and the oropharynx to get to the larynx= shared pathway (air and food)
function of the larynx
-
Airway protection
- Larynx protects the airway when we eat and drink
-
Ventilation
- Conduit for air to pass for breathing
-
Cough reflex
- Rapidly expels anything inadvertently entering the airway
- Production of sound (phonation)
Anatomy of the larynx
- Larynx sits in front of the pharynx
- Tube supported by cartilaginous tube, ligaments and membrane
- Muscle also help support
the larynx is suspended fromt he
hyoid bone
where does the larynx begin
- Begins at the laryngeal inlet and ends at the lower border of cricoid cartilage (C6- trachea)
- Continues as the trachea
laryngeal inlet is circles in yellow makrer
larynx relationship between the suprahyoid and infrahyoid muscles
where does the larynx lie anteriro to
the laryngopharynx
posterior view of the larynx
- Posterior-laterally to laryngeal inlet the ………. …………is found
piriform fossa
- When we eat and drink the position of the epiglottis moves to a more
- horizontal position–> directing food through the piriform fossa and into the oesophagus
- Food can get stuck in the piriform fossa
Framework of larynx - Cartilage
- Thyroid (2 lamina – superior and inferior horn)
- When one lamina meets the other lamina = laryngeal prominences – Adams apple
- cricoid cartilage -below thyroid
- inferior horn of thyroid cartilage articulates with the cricoid cartilage- synovial joint
- thicker at the back than front (signet ring)
- Retinoid cartilage- sits on the cricoid cartilage
- Epiglottis- attached by its stalk to the inner surface of the thyroid cartilage
Framework of the larynx: Membranes
Connective tissue sheet- named according to structures they are attached to
Surface anatomy : certain cartilages and membranes are palpable
laryngeal inlet
- Oval shaped
- Made up of
- Epiglottis
- Aryepiglottic folds
- Formed by the superior border of the quadrangular membrane
- Inferior border- false vocal cord
Cricothyroid membrane
Free superior margin of the cricothyroid membrane and quadrangular membrane- true vocal cord
Larynx is lined with a
mucous membrane
- Internal anatomy is shaped by
- folds formed by ligaments/membranes and cartilages
- Quadrangular membrane (inferior boundary)- false vocal cord
- Superior extension of the cricothyroid membrane- true vocal cord
Larynx can be separated into three regions by mucosal folds
- Supraglottic
- Glottis
- Infraglottis
Supraglottic
x
- From laryngeal inlet down to the false vocal cords
- Glottis
- True vocal cords to about 1cm below here
- Narrowest part of larynx
- Infraglottis
Below the glottis
betwen the vocal cords (false and true) there is an
- Outpouching of mucous membrane from between the vocal cords–> saccule of larynx
- Between vestibular and vocal folds in small recess (ventricle)–> leads laterally and upwards into saccule (or sinus)à contains mucous glands that keep the true vocal fold moist
truve vocal cords are covered in
- Stratified squamous epithelium
- More resistant to damage
the larynx with the excpetion of the true vocal cords are lined with
pseudostratified ciliated columnar epithelium
laryngoscopic view of larynx e.g. during intubation
when will the larynx be visualise
intubation
flexible nasoendoscopy
intubation
vocal cords mst be views for intubation: placement of an endotracheal tube in subglottic region (i.e. below vocal cords)
flexible nasoendoscopy
insert flexible endoscope via nasal cavity and pharynx to then visualise larynx
the intrinsic larngeal muscles have 2 main actions
-
to alter
- Size/shape of laryngeal inlet
-
Tension/position of vocal cords
- Protection- swallowing food
- When speaking and coughing and breathing
when we swallow what happens to the laryngeal inlet and vocal cords
close laryngeal inlet and vocal cords
protecting resp tract
during inspiration and expiration what happens to the laryngeal inlet and vocal cords
laryngeal inlet and vocal cords open
- allowing movement of air
what happens to the vocal cords during phonation
partially adducted - vocal cords come together
what happens to the vocal cords during coughing
must go from foricble adduction 9to increase itnrthoarcic pressure) –> abducted
outline how the vocal cords are moved to allow coughing and phonation i.e. adduction/abduction of the vocal cords
- Vocalis muscle run along the length of the vocal cords
- muscles associated with arytenoid cartilage causes widening of aperture
- responsible for moving outwards and inwards of vocal cords
- important one= posterior cricoarytenoid (only intrinsic muscle that acts to abduct vocal cords)
- all the other intrinsic muscles will act to adduct vocal cords
- responsible for moving outwards and inwards of vocal cords
only intrinsic muscle that acts to abduct vocal cords
important one= posterior cricoarytenoid
the rest of the intrinsic muscles will act to adduct the vocal cords
- intrinsic muscle move cartilage
relative to one another playing a key role in vocal cord movement
- arytenoid position on cricoid determines
position of true vocal cords and therefore size of aperture (glottis)
all intrinsic muscles are supplied by the …………. …………… …………… excet the ………………..
- all muscles supplied by the recurrent laryngeal nerve of vagus (CN X) except cricothyroid muscle
reight/left vocal cord muscles supplies by the
right/left recurrent laryngeal nerve
cricothyroid muscle supplies by the
external branch of the superior laryngeal nerve
Cricothyroid muscle summary
- Intrinsic muscle
- Found on the outside of the cartilages
- external branch of superior laryngeal nerve
- will icnrease tension on vocal cords- importan for reaching higher pitches
vocal cord movements: inspiration and expiration
- Vocal cords aBduct
- Allows air to pass in and out
Vocal cord movements:
- Phonation
- VC closely aDduct
Vocal cord movements: Cough (explosion of compressed air)
- insire and fill lungs with air
- vocal cords the aDduct
- expiratory muscles contract
- intrathroaric pressure builds
- then cords suddenly abducted
- explisuve outflow of air
both vocal cords have to emet in the midline (aDduct) to allow for
phonation and cought
if movement of one vocal cord is impaired (e.g. injury to nerve supplying muscles involved in its moveemnt) ….
phonation and cough will be impaired
what is this patient doing
B- breathing in
pitch of sound determined by
vocal cord tension
- High pitched sounds
Vocal cords taut
- Low pitched
Vocal cords less taut
what will icnrease the tension of the vocal cords outside the larynx
Bilateral contraction of cricothyroid muscle
cricothryoid muscle is innervated by
CNX - vagus
external branch of the superior largngeal nerve
external branch of the superiro laryngeal supplying the cricothyroid muscle is closely associated to and at risk during
(closely related to superior thryoid artery)–> can be damaged during thryoid surgery
- will cause hoarseness of voice particulalry when attempting higher pitched sounds
Action of cricothyroid muscle
Tilts thyroid cartilage forward on cricoid increasing tension on vocal cords–>important for reaching higher pitch
- When epiglottis is open
air, food and water can go into the larynx
- Epiglottis needs to close during
- swallowing
- Directs food to the oesophagus instead of the airway
outline what happens to the larynx when we swallow
- Hyoid bone elevated and moves anteriorly by suprahyoid muscles
- Larynx moves up and forward
- Tongue pushes epiglottis posteriorly and aryepiglottic muscles contract
- Narrowing laryngeal inlet
- Brining epiglottis from a vertical to a more horizontal position (longitudinal pharyngeal muscles)
- Directs food into the piriform fossa into the oesophagus
- Closure of vocal cords (glottis)
Hyoid bone elevated and moves anteriorly by suprahyoid muscles
helps ensure patency of pharynx so food/fluid can be directed into it
vagus nerve innervation to the larynx summary
- Autonomics will also be delivered via CN X to mucosal glands within the larynx
superior laryngeal nerve
- a branch of the vagus
- gives rise to an internal and external branch
- runs very closely to the superior thyroid artery
internal branch of the superior laryngeal nerve
purely sensory (supraglottic)
external branch of the superior laryngeal nerve
motor to cricothyroid
recurrent laryngeal nerve route
- arises distally from the vagus
- passes anteriorly to then loops under right SCA (superior cerebellar artery) and on left, arch of the aorta
- asends in tracheo-oesophageal groove
- close anatomical relationship with thryoid gland and inferior thyroid arteries supplying the gland
RLN has a close anatomical relationship with the thyroid gland and inferior thryoid arteries- how does the RLN ascend
in the tracheo-oesophageal groove
Vocal cord palsies
Injury to recurrent laryngeal nerve
example of causes of vocal cord palsies due to injruy to the RLN
- thyroid sugery- RLN closely related to inferior thyroid artery
- Aortic arch aneurysm (left RLN)
- Cancer involving apex of lung (right RLN) (pancoast tumour)
- Disease or surgery involving larynx, oesophagus or thyroid
- Unilateral lesions lead to unilateral vocal cord palsies
- Hoarse voice
- Ineffective cough
- Hoarse voice
the paralysed vocal cord assumes a paramedian position
- between fully abducted and fully adducted
- often the contralateral side will compensate in tiem 9crosses midline to meet vocal cord on affecte dside)
- Bilateral lesions of the RLN
- Both vocal cords paralysed and in paramedian position
- Narrow glottis
- Significant airway obstruction… emergency surgical airway e.g. cricothyroidotomy, tracheostomy
Summary of the larynx
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