H&N 12 Flashcards
what structure does the isthmus of the thyroid gland lie just below?
the cricoid cartilage
blood vessels to and from thyroid gland?
superior thyroid artery from ECA which forms A and P branches at upper poles of L and R lobes
inferior thyroid artery from thyrocervical trunk off subclavian artery, which also supplies blood to upper 1/3 of oesophagus
superior, middle and inferior thyroid veins which are tributaries of IJV which drains into the subclavian vein to enter SVC
to what cartilages does the cricothyroid muscle attach to?
thyroid and cricoid cartilages (above and below respectively)
where are the piriform fossae of the laryngopharynx formed?
at the laryngeal inlet (on each side)
what is the pharyngeal muscle layer covered by internally?
pharyngobasilar fascia, which is covered by the mucous membrane
what does the laryngopharynx lie posterior to?
laryngeal inlet (and larynx)
what is the larynx located between?
the hyoid bone above (C3) and the trachea below
so lies between C4 and C6
structures forming framework of larynx?
epiglottis, thyroid and cricoid cartilages=unpaired
paired arytenoid cartilages, cuneiform and corniculate
how is the larynx attached to the hyoid bone above?
by the thyrohyoid membrane and the thyrohyoid muscle- an infrahyoid muscle
other infrahyoids= sternothyroid, sternohyoid, omohyoid
attachments of epiglottis?
anter= body of hyoid= from 2nd and 3rd pharyngeal arch cartilages
poster= back of thyroid cartilage
sides connected to arytenoids by aryepiglottic folds- run bwards to form margins of aditus of larynx
what is the laryngeal prominence?
where the 2 lateral plates of the thyroid cartilage meet in the midline in a prominent V= Adam’s apple
attachment of cricoid cartilage inferiorly?
to trachea by cricotracheal membrane= connects all cartilages and its upper edge is slightly thickened to form vocal ligament.
anteriorly thickened as cricothyroid ligaments= easily felt and used in emergency for cricothyroid puncture for laryngeal obstruction
at what vertebral level is the pharynx continuous with the oesophagus?
C6
what is the uvula?
cone-shaped process of the soft palate-lies posterior to hard palate
what cartilage does the cricoid cartilage attach to inferiorly?
the 1st cartilaginous ring of the trachea ( an incomplete cartilage posteriorly where trachealis muscle located, but cricoid is a complete cartilage)
what does the criocthyroid muscle do to the VCs?
it tenses them
what does the posterior cricoarytenoid muscle on each side do?
rotates the arytenoids outwards, so separating the VCs
innervation of mucosa above VCs in larynx?
internal laryngeal nerve from superior laryngeal
innervation of mucosa below VCs?
recurrent laryngeal nerve
why do the VCs not become oedematous with URTIs?
absence of intervening SM between mucosa and vocal ligament so no fluid can collect underneath the VCs
effect of superior laryngeal nerve damage on phonation?
some wkness results as loss of tightening effect of cricothyroid muscle on VC as innervated by this nerve
what may be the solution to bilateral recurrent laryngeal nerve damage?
tracheotomy- can open a direct airway with trachea by creating a hole in anterior part of neck
position of VC if RLN damaged?
neutral/paramedian position between abduction and adduction
what is a pharyngeal pouch?
a posterior herniation of pharyngeal mucosa= true diverticulum
occurs through Killian’s dehiscence- between inferior constrictor and cricopharyngeus
which membrane can be perforated in an emergency to gain access to the airway below the level of the vocal folds of the larynx?
cricothyroid (cricovocal) membrane, which is palpable in midline, allows access to infraglottic space of airway
what is the vocal ligament?
the upper, free, thickened margin of the cricothyroid membrane running between the deep surface of angle of thyroid anteriorly and arytenoid cartilages (from vocal processes) posteriorly, and is found within the VCs
sensory innervation of laryngeal cavity above and below vocal folds (cords)?
above= superior laryngeal nerve below= recurrent laryngeal nerve
why does the R recurrent laryngeal nerve originate in root of neck, where L originates in superior mediastinum of thorax?
embry. development of aortic arches: 6th aortic arch gives rise to R pulm artery on R side but distal part of arch regresses so R nerve moves upwards to hook underneath R subclavian artery from 4th aortic arch. On L, 6th aortic arch gives rise to L pulmonary artery and distal part of arch persists as the ducuts arteriorsus so L nerve does not move upwards and hooks underneath arch of aorta from 4th aortic arch.
functions of larynx?
sphincter- protects air passages during swallowing, guarding entrance to trachea
ability to close glottis also necessary for cough reflex- so intrapulmonary pressure can be raised for a forceful expulsion of air, and for straining
phonation- due to vibration of VCs during expiration of air through narrowed glottis
borders of larynx?
opens into laryngopharynx superiorly
continuous with trachea infer.
infrahyoid muscles cover larynx anteriorly
upper parts of thyroid gland lobes laterally
laryngopharynx lies posteriorly
what does the inferior cornu (horn) of thyroid cartilage articulate with?
the cricoid cartilage creating a synovial joint which allows tilting movements
composition of epiglottis?
fibroelastic cartilage
attaches to posterior of hyoid bone and thyroid cartilage e.g. by thyroepiglottic ligament
attachments of thyroid cartilage?
comprise 2 lamina and 2 horns
superior horn to hyoid bone via thyrohyoid ligament
synovial joint with cricoid cartilage via inferior horn
oblique line= strap muscles
shape of cricoid cartilage
signet ring
2 articular facets on each side of cricoid cartilage are for what?
inferior horn of thyroid cartilage
aryetenoid cartilage
importance of anatomical location of cricoid cartilage?
found at C6 and can be used as a landmark for palpating CCA pulse without risk of reflex bradycardia from stimulating the carotid sinus at level of C4
shape and processes of arytenoid cartilages?
pyramid
vocal and muscular processes, vocal anteriorly to which VCs attach, and muscular laterally
how is the larynx suspended from the hyoid bone?
by the thyrohyoid membrane
margins of laryngeal inlet?
upper edge of epiglottis
aryepiglottic folds laterally covering the quadrangular membrane which links the epiglottis to the arytenoid cartilage
arytenoid cartilage
name of emergency procedure in acute laryngeal obstruction?
cricothyroidotomy
when would a tracheostomy be performed?
as a planned procedure if LT +ve ventilation of lungs required e.g. due to resp muscle paralysis
why might asphyxia occur?
laryngeal oedema e.g. anaphylaxis, of infection- acute epiglottitis e.g. from H.influenzae, and croup
inhalation of FB
laryngeal tumour
laryngeal carcinoma RFs?
male
smoking
alcohol
why is spread of VC carcinoma delayed?
absence of SM and hence blood vessels for metastasis
VC epithelium and importance?
stratified squamous non-keratinized
can withstand wear and tear resulting from air flow across them
what in addition to the vocal ligament is contained by each VC?
the vocalis muscle
position of VCs in phonation?
cords adducted but not completely closed so VCs capable of vibrating
which is the only intrinsic laryngeal muscle to abduct the VCs?
the posterior cricoarytenoid
so muscle paralysis would necessitate emergency tracheostomy to restore breathing
cavities of larynx?
supraglottic space= inlet above false VCs
glottis= VCs and rima glottidis, area between true and false VCs known as ventricle
subglottic space= below true VCs to lower border of cricoid cartilage
why do VCs appear pearly white on laryngoscopy?
no SM
and hence no oedema occurs here
what do the piriform fossae lie either side of?
the aryepiglottic folds covering the quadrangular membrane connecting epiglottis with cricoid cartilage
movements of arytenoid cartilages?
laterally and medially
rotation around vertical axis
extrinsic laryngeal muscles?
supra and infrahyoid
note geniohyoid and thryohyoid innervated by C1
other infrahyoid by ansa cervicalis
intrinsic laryngeal muscle which tenses VCs?
cricothyroid
intrinsic laryngeal muscle which adducts VCs?
lateral cricoartytenoid
muscles approximating VCs?
oblique and transverse artytenoids
muscle which relaxes VCs?
vocalis
in what does the recurrent laryngeal nerve course up to larynx?
tracheo-oesophageal groove
blood supply to larynx?
superior and inferior laryngeal arteries from s and i thyroid respectively
superior and infer laryngeal veins
why are branches of vagus nerve at risk of damage in a thyroidectomy?
SLN accompanied by STA and RLN accompanied by ITA and arteries ligated in a thyroidectomy
so pre-op VC check important
laryngeal disorders that can cause hoarse voice?
laryngitis GORD laryngeal carcinoma benign nodules on VCs overuse of VCs
how can VCs be assessed in patient with a hoarse voice?
laryngoscopy:
indirect using an angled mirror
or flexible rhinolaryngoscopy
3 symptoms of a laryngeal carcinoma?
persistent hoarseness
otalgia- vagus nerve innervates larynx and the outer plate of tympanic membrane
dysphagia
types of laryngeal cancer and which has best prognosis and why?
supraglottic carcinoma
cancer of VCs
subglottic
VC carcinoma good prognosis and presents with early with symtoms seen easily, and delayed spread due to absence of vascular SM
why is C6 vertebral level important in neck?
carotid tubercle- CCA pulse can be felt by compressing artery against tubercle
junction of pharynx with oesophagus, and larynx with trachea
level at which vertebral artery enters transverse foramen of C6 vertebra
what is the levator glandulae thyroideae?
The levator glandulae thyroideae is a fibrous band which connects the isthmus of the thyroid gland to the
hyoid bone. It may contain muscle. More muscle= hyoid bone raised more effectively.
importance of infrahyoid muscles in swallowing?
oppose actions of suprahyoid muscles elevating hyoid bone and larynx, hence stabilise larynx
why does thyroid move during swallowing?
thyroid gland enclosed within visceral part of pre-tracheal layer of deep cervical fascia, which attaches to the thyroid and cricoid cartilages of the larynx, so movement of larynx during swallowing means thyroid gland moves with it
why is inferior thyroid artery from thyrocervical trunk not damaged during elevation of thyroid during swallowing?
artery is tortuous in structure
