Unit 1 Respiratory 1: Airway Anatomy Flashcards
What are the intrinsic muscles of the larynx used for?
Phonation and/or vocal cord movement
What are the extrinsic muscles of the larynx used for?
Support the larynx inside the neck
Where do the true vocal cords attach anteriorly and posteriorly?
Anteriorly: to the thyroid cartilage
Posteriorly: to the arytenoid cartilage
Cricothyroid:
Function
Primary outcome of muscle contraction
Innervation
Function: adjusts length (tension) of the vocal ligaments
Primary outcome of muscle contraction: elongates (tenses)
Innervation: SLN (external)
Vocalis:
Primary outcome of muscle contraction
Innervation
Function: adjusts length (tension) of vocal ligaments
Primary outcome of muscle contraction: shortens (relaxes)
Innervation : RLN
Thyroarytenoid:
Primary outcome of muscle contraction
Innervation
Function: adjusts length (tension) of vocal ligaments AND glottic diameter
Primary outcome of muscle contraction: shortens (relaxes) AND adducts vocal folds (narrows glottis)
Innervation: RLN
Lateral cricoarytenoid:
Function
Primary outcome of muscle contraction
Innervation
Function: glottic diameter
Primary outcome of muscle contraction: adducts vocal folds (narrows glottis)
Innervation : RLN
Posterior cricoarytenoid
Function
Primary outcome of muscle contraction
Innervation
Function: glottic diameter
Primary outcome of muscle contraction: abducts vocal folds (widens glottis)
Innervation: RLN
Sphincter function of aryepiglottic? Interarytenoid?
Aryepiglottic: closes laryngeal vestibule - RLN
Interarytenoid: closes posterior commisure of glottis - RLN
What 6 extrinsic muscles elevate the larynx in the neck for breathing and swallowing?
Stylohyoid Geniohyoid Mylohyoid Thyrohyoid Digastric Stylopharyngeus
What 3 extrinsic muscles depress the larynx within the neck for breathing and swallowing?
Omohyoid
Sternohyoid
Sternothyroid
What nerve does the SLN branch off of and where?
SLN branches off of the vagus nerve just beyond the jugular foramen at the skull base
At what level does the SLN divide? What does it divide into?
At the level of the hyoid, the SLN divides into the internal and external branches
What does the internal branch of the SLN penetrate?
The thyrohyoid membrane between the greater Cornu of the hyoid bone
Where does the external branch enter?
The cricothyroid muscle
What does the RLN branch off of and where?
The RLN branches off of the vagus nerve inside the thorax
Both the right and left RLNs make loops before ascending tracheoesophageal groove to joint larynx, where do each loop?
Right RLN: loops under the subclavian artery
Left RLN: loops under the aortic arch
Which RLN is more susceptible to injury and why?
Due to its location in the thorax the left RLN is more susceptible to injury
What 4 nerves provide sensory innervation of the airway?
Trigeminal (CN V)
Glossopharyngeal (CN IX)
Superior laryngeal
Recurrent laryngeal
Describe Trigeminal (CN V) sensory innervation of the airway
V1: ophthalmic (anterior ethmoidal) - nares & anterior 1/3 of nasal septum
V2: maxillary (sphenopalatine) - turbinates & septum
V3: mandibular (lingual) - anterior 1/3 of tongue
Describe the glossopharyngeal (CN IX) sensory innervation of the airway
Soft palate Oropharynx Tonsils Posterior 1/3 of tongue Vallecula Anterior side of epiglottis
What is the afferent limb of the gag reflex?
Glossopharyngeal (CN IX)
Describe the superior laryngeal nerve sensory innervation of the airway
Internal branch: posterior side of the epiglottis to level of the vocal cords
The external branch provides motor only, not sensory innervation
Describe the recurrent laryngeal nerve sensory innervation of the airway
Below level of vocal cords to trachea
Describe the superior laryngeal nerve motor innervation of the larynx
External branch: cricothyroid muscle - tense vocal cords
Internal branch provides sensory innervation only
Describe recurrent laryngeal nerve motor innervation of the larynx
All intrinsic muscles except cricothyroid
SLN injury causes what?
Hoarseness because the vocal cords can’t be tensed
Injury to the RLN causes what?
Depends on unilateral or bilateral injury:
Unilateral - results in paralysis of the ipsilateral (same side) vocal cord abductors and does not cause respiratory distress
Bilateral - results in bilateral paralysis of the vocal cord abductors, tensing action of the cricothyroid muscles act unopposed -> stridor and respiratory distress
What about chronic injury of the RLN?
Well tolerated and does not cause respiratory distress
Name 6 things that can cause RLN injury to either side
External pressure from ETT tube External pressure from LMA Thyroid surgery Parathyroid surgery Neck stretching Tumor
Name 4 things that can cause injury to the right RLN only
PDA ligation
Left atrial enlargement (mitral stenosis)
Aortic arch aneurysm
Thoracic tumor
Name the 3 infiltration airway blocks
Glossopharyngeal block
Superior laryngeal block
Transtracheal block
Glossopharyngeal block:
Needle insertion site
Aspiration
Injected amount
Needle insertion site: at the base of the palatoglossal arch (anterior tonsillar pillar) at a depth of 0.25 - 0.5 cm
Aspiration: air - too deep; blood - withdrawal and redirect medically (carotid is very close)
Injected amount: 1 - 2 mL of LA on both sides
SLN block:
Needle insertion site
Aspiration
Injected amount
Needle insertion site: inferior border of the greater Cornu of the hyoid bone
Aspiration: air - too deep
Injected amount: 1 mL injected above the thyrohyoid membrane then 2 mL injected 2 - 3 mm beneath it