Larynx & Pharynx Flashcards
Describe the larynx
Modified upper part of the respiratory tract made up of cartilages, ligaments, muscles and lined with mucous membranes.
Functions of the larynx
- Protection of lower respiratory tract
- Effort closure: coughing, sneezing, abdominal straining
- Phonation: relies on precise balance of activity of all intrinsic muscles of the larynx
Common laryngeal insults
- Inflammation - laryngitis (inflammation of vocal cords causing hoarseness or aphonia)
- Neoplasms - carcinoma (mainly squamous cell - especially in smokers)
- Vocal nodules
NB: laryngeal nerves at risk during thyroid surgery
Relations of the larynx
Located in anterior triangle of neck
- Superiorly: hyoid bone (level of C3)
- C4: CCA bifurcates (thyroid cartilage, sup border)
- Inferiorly: trachea
Cartilages of the larynx
3 unpaired:
- Cricoid
- Thyroid
- Epiglottis
1 paired:
- Arytenoids
* i.e. 5 cartilages in total*
Discuss the epiglottis
- Leaf-shaped ‘yellow-elastic’ cartilage
- Never calcifies
- NB: other laryngeal cartilages = hyaline
- Tip rises ~1cm above the hyoid
- Mucous membrane reflected from its anterior surface to the back of the tongue
- Forms the glossoepiglottic folds
Discuss the glossoepiglottic folds
- 3 longitudinal ridges
- Valleculae are depressions either side of the median fold
- Piriform fossae are depressions inferior to the lateral folds
Where are foreign bodies likely to lodge?
Sites of natural constriction/blind-ending structures
- Base of tongue
- Tonsils
- Valleculae
- Piriform fossae
Discuss the cricoid
Signet ring - lamina much taller than arch - C6-7
- Only complete cartilaginous ring in resp tract
- Foundation of laryngeal skeleton
- Articulates with thyroid & arytenoid cartilages
Articulations of cricoid
- Facets on superior rim for arytenoids
- Facets on external surface for inferior horn of thyroid cartilage
Discuss the thyroid cartilage
C4-5
- Two pentagonal laminae fused anteriorly to form the laryngeal prominence
- M ~90º, F ~120º (little difference in children)
- Posterior projects superiorly & inferiorly
- Superior/inferior horns (cornu)
Effect of puberty on the larynx
Enlargement of all cartilages in males produces the laryngeal prominence
Length of vocal cords nearly doubled but change in pitch in males due to mass/structural changes
Discuss the arytenoid cartilages
- Triangle-based pyramid, apex superiorly
- Anterior point elongated - vocal processes
- Lateral projections - muscular processes
- Muscle attachments
- Base articulates with cricoid lamina
- Synovial joint - rotation/gliding
Laryngeal membranes
- Thyrohyoid membrane
Intrinsic membranes:
- Quadrangular membrane
- Cricothyroid membrane
Discuss the thyrohyoid membrane
- Upper border of the thyroid cartilage → upper border of the posterior surface of the hyoid bone
- Pierced by superior laryngeal vessels & internal laryngeal branch of superior laryngeal n.
Two thickenings:
- Midline: median thyrohyoid ligament
- Posterior edges: lateral thyrohyoid ligaments
- Superior horn → greater horn
Discuss the quadrangular membrane
- Fibroelastic: epiglottis → arytenoid cartilages
- Upper margins form aryepiglottic folds
- Lower margins form vestibular folds (false cords)
Discuss the cricothyroid membrane
- Highly elastic
- Superior rim of cricoid arch & vocal process of arytenoids → internal surface of thyroid angle
- Superior edge forms vocal ligaments
- Together with overlying membrane = vocal folds
- Thickening of anterior fibres: median cricothyroid ligament
Discuss surgical airway access
- Emergency: pierce median cricothyroid ligament to gain access to subglottic airway if choking
- Elective tracheostomy: between 2nd/3rd tracheal rings
Interior of larynx - diagram
Describe the laryngeal inlet
Communication of larynx & pharynx, boundaries:
- Anteriorly: epiglottis
- Posteriorly: arytenoids
- Laterally: aryepiglottic folds
Discuss the vestibule
Space from laryngeal opening → vestibular folds
Discuss the ventricle
Space produced by small amounts of membrane herniating through an opening in the saccule
Contains the mucous glands: lubricate vocal cords
Discuss the glottis & rima glottidis
Glottis: formed by the two vocal folds
Rima glottidis: space within glottis
Discuss the epithelium lining the larynx
Vocal cords/epiglottis:
- Non-keratinising stratified squamous
- Thickened on cords: greater wear & tear
Rest:
- Pseudostratified ciliated columnar (respiratory)
Functional groups of intrinsic laryngeal muscles
- Action on laryngeal inlet
- Abduction-adduction of vocal cords
- Changes in length and tension of vocal cords
Muscles with an action on laryngeal inlet
- Aryepiglotticus: closes inlet
- Runs in aryepiglottic fold, extension of oblique arytenoids
- Thyroepiglotticus: opens inlet
Muscles which abduct/adduct vocal cords
- Posterior cricothyroid: sole abductor of cords
- Posterior surface of cricoid lamina → muscular process of ipsilateral arytenoid
- Lateral arytenoids & interarytenoids: adductors
NB: motion occurs at the cricoarytenoid joints
Muscles which alter length/tension of the vocal cords
- Cricothyroid: increases tension (thyroid cartilage moves forward)
- Thyroarytenoid: decreases tension (and adducts)
- Medial part = vocalis lies in vocal fold
- Decreases length and alters thickness
- Effect on pitch dep. on other muscles
- Medial part = vocalis lies in vocal fold
Extrinsic muscles of the larynx
- Elevators of the larynx:
- Via hyoid: mylohyoid, stylohyoid, geniohyoid & digastric
- Directly: stylopharyngeus, palatopharyngeus, salpingopharyngeus
- Depressors of the larynx:
- Via hyoid: sternohyoid, omohyoid & thyrohyoid
- Directly, sternothyroid
NB: generally elevated larynx returns to rest by elastic recoil of trachea. Active depression occurs in deep inspiration
Innervation of intrinsic muscles of the larynx
- Recurrently laryngeal nerve (X) except cricothyroid:
- External branch of superior laryngeal nerve (X)
- Only muscle on external surface
How do neurovascular structures enter the larynx?
Above vocal cords: pierce thyrohyoid membrane
Below vocal cords: enter/leave beneath inferior constrictor of pharynx
Arterial & venous supply to larynx
Above vocal cords:
- Superior laryngeal branch of superior thyroid artery (from ECA)
- Superior laryngeal veins (→ superior thyroid veins → IJV)
Below vocal cords:
- Inferior branch of inferior thyroid artery (from thyrocervical trunk of subclavian)
- Inferior laryngeal veins (→ inferior thyroid veins → brachiocephalic vein, mainly left)
Lymphatic drainage of larynx
Above vocal cords:
- Anterosuperior group of deep cervical nodes
Below cords:
- Posteroinferior group of deep cervical nodes
Innervation of the larynx
Above the vocal cords
- Mucosal sensation: internal branch of the superior laryngeal nerve (X)
- Sympathetic: from superior cervical ganglion
Below the vocal cords
- Mucosal sensation: recurrent laryngeal nerve (X)
- Middle cervical ganglion
NB: sympathetics run with arteries
Discuss recurrent laryngeal nerve injury
- Unilateral: affected cord semi-abducted, other cord crosses midline to compensate = minimal defects to phonation
- Bilateral: both cords semi-abducted = difficulties in: protecting glottis, phonation & coughing
- Very serious
Discuss external branch of the superior laryngeal nerve damage
- Problems with phonation: esp at higher freq
- If internal branch also injured, supraglottic sensation may be lost
NB: intraoperative electrophysiological monitoring of nerves during thyroid surgery
Describe sequence of swallowing
- Closure of vestibular & vocal folds
- Closure of laryngeal inlet (aryepiglotticus)
- Elevation of larynx (extrinsic muscles)
- Protection of inlet with epiglottis, flaps down
NB: once bolus reaches oesophagus, inlet opens to resume respiration, epiglottis/larynx return to rest by elastic recoil
Discuss effort closure
Vocal cords powerfully abducted:
- Coughing: cords suddenly abducted = explosion of air
- Straining: closed cords prevent upward displacement of diaphragm - increases intra-abdominal pressure
Discuss the Valsalva manoeuvre
- Contraction of abdominal wall muscles against closed glottis with lungs filled
- Increases intra-abdominal and intrathoracic pressures
- Useful in expelling faeces, parturition & coughing (sudden abduction)
Discuss laryngitis
- Inflammation of larynx/vocal cords due to infection or chemical irritation
Presentation:
- Breathing harsh & difficult, coughing painful
- Voice becomes husky or lost completely
‘Treatment’:
- Remain in warm, moist atmosphere & rest voice
Discuss the effect if cigarette smoke
Paralyses cilia and can result in squamous metaplasia, a precursor for cancer
Discuss the position of the larynx & implications
- At birth: superior tip of epiglottis lies behind the soft palate
- Oropharynx is very small & develops concomitantly with descent of larynx
- Position allows simultaneous swallowing and breathing - outgrow this before larynx descends
Discuss the trachea
- Midline structure from cricoid cartilage → carina
- Composed of c-shaped tracheal rings
- Embedded in connective tissue of trachea
- Rings deficient posterior: spanned by trachealis
- Smooth muscle, contract decrease tracheal diameter - reduce dead space in quiet respiration
- Mucosa = ciliated pseudostratified columnar
- Especially sensitive to irritation at carina
Blood supply to trachea
Branches of interior thyroid & bronchial arteries
Tracheal lymph drainage
Upper part: paratracheal & deep cervical nodes
Lower part: tracheobronchial nodes
Innervation of trachea
Sensory & secretomotor: recurrent laryngeal n.
Sympathetic: thoracic sympathetic chain
Relations of trachea in the neck
- Oesophagus posteriorly - can bulge trachealis in swallowing
- Thyroid
- CCA, IJV
- Phrenic & vagus nerves
- Recurrent laryngeals ascend bilaterally between trachea & oesophagus
Describe the pharynx
- Fibromuscular tube extending from the base of the skull to the lower border of the cricoid
- Has three parts: naso-, oro- & laryngo-pharynx
- Posterior to nasal cavity, oral cavity & larynx
Muscles of the pharynx: outer layer
The constrictors - insert on midline pharyngeal raphé
- Superior: arises from pterygomandibular raphé
- Middle: arises from stylohyoid ligament & horns of the hyoid
- Inferior: arises thyroid & cricoid cartilages
- Lower fibres = cricopharyngeus: don’t insert into midline raphé
Muscles of the pharynx: inner layer
- Stylopharyngeus: arises from styloid process
- Palatopharyngeus: from palatine aponeurosis
- Salpingopharyngeus: medial end of aud. tube
Pull larynx & pharynx upwards during swallowing
Innervation to pharynx
Motor:
- Pharyngeal nerves (X) from pharyngeal plexus
- XI Cranial root contributes motor fibres to X
- Inferior constrict receives additional fibres from external & recurrent laryngeal n.s (X)
Sensation:
- Branches of glossopharyngeal (IX)
- Nerves convey preganglionic parasymp. fibres to pharyngeal glands
Discuss lymphatic tissue at the entrance of the respiratory/digestive tract
Waldeyer’s ring: 4 groups of specialised lymphatic tissue at entrance to the respiratory/digestive tracts
- Pharyngeal tonsils
- Tubal tonsils - medial end of auditory tube
- Palatine tonsils - between palatoglossal & palatopharyngeal arches in oropharynx
- Lingual tonsils - posterior surface of tongue
Discuss tonsilitis
- Enlarged, inflamed tonsils due to infection
- If chronic may have to be removed: tonsillectomy
- Facial artery: many branches to tonsillar bed
- Post-op haemorrhage may occur, stay overnight
- May have referred pain to ear: IX gives tonsillar branches & innervates middle ear
