Airway Anatomy Flashcards
What is the sensory innervation of the anterior tongue?
Trigeminal (V) V3 - mandibular branch
What nerve innervates the posterior tongue?
Glossopharyngeal (IX)
Which nerve is responsible for the sensory innervation of the soft palate?
Glossopharyngeal (IX)
What nerve innervates the oropharynx?
Glossopharyngeal (IX)
What is the sensory innervation of the vallecula?
Glossopharyngeal (IX)
Which nerve provides sensory innervation to the anterior epiglottis?
Glossopharyngeal (IX)
What nerve is responsible for the sensory innervation of the posterior epiglottis at the level of the vocal cords ?
Superior laryngeal internal branch (X)
What innervates the laryngeal mucosa up to the level of the vocal cords?
Superior laryngeal internal branch (X)
Which nerve innervates the laryngeal mucosa below the level of the vocal cords?
Recurrent laryngeal nerve
* footnote**
Part of the Vagus Nerve
What nerve provides sensory innervation to the below the vocal cords/ trachea?
RLN of the Vagus (X)
What are the two branches of the vagus nerve that provide innervation to the larynx?
The superior laryngeal nerve (SLN) internal branch and the recurrent laryngeal nerve.
The SLN has both an external and an internal branch.
What does the external branch of the superior laryngeal nerve innervate?
The cricothyroid muscle.
This is the only muscle that tenses (elongates) the vocal cords.
What is the function of the internal branch of the superior laryngeal nerve?
It is purely sensory.
Which nerve innervates all of the other intrinsic laryngeal muscles?
The recurrent laryngeal nerve.
Does the glossopharyngeal nerve innervate the larynx?
No, it does not innervate the larynx.
What is the function of the posterior cricoarytenoid muscle?
The posterior cricoarytenoid is the only muscle that ABducts the vocal cords.
What is the function of the cricothyroid muscle?
The cricothyroid is the only muscle that tenses (elongates) the vocal cords.
What is the function of the aryepiglottic muscle?
The aryepiglottic closes the laryngeal vestibule.
What is the function of the lateral cricoarytenoid muscle?
The lateral cricoarytenoid ADDucts the vocal cords.
How does the right RLN differ from the left RLN?
The right RLN loops under the right subclavian artery, while the left RLN loops under the aorta.
This anatomical difference makes the left RLN more susceptible to injury.
What are the causes of left RLN injury?
Causes of left RLN injury include: Mitral stenosis, PDA ligation, aortic arch aneurysm, and thoracic tumor.
Mitral stenosis may present as hoarseness due to left atrial enlargement compressing the nerve.
What are the causes of RLN injury that can affect both sides?
Causes of left or right RLN injury include: parathyroid or thyroid surgery, external pressure from an LMA or ETT, neck tumor, and neck extension.
How many cartilages make up the larynx?
The larynx consists of 9 cartilages (3 paired and 3 unpaired).
What are the paired cartilages of the larynx?
The paired cartilages are corniculate, arytenoid, and cuneiform.
What are the unpaired cartilages of the larynx?
The unpaired cartilages are epiglottis, thyroid, and cricoid.
What is the trigeminal nerve (CN 5)?
The primary nerve that provides sensory innervation to the face and head.
How many branches does the trigeminal nerve divide into?
It divides into 3 branches.
What does V3 of the trigeminal nerve provide motor wise?
Motor innervation to muscles of mastication (chewing).
It does not provide motor innervation to the tongue (tongue movement is a function of the hypoglossal nerve CN 12).
What does V1 (Ophthalmic) sensory innervate?
Nares and anterior 1/3 of nasal septum.
What does V2 (Maxillary) sensory innervate?
Turbinates and septum
What does V3 (Mandibular) sensory innervate ?
Anterior 2/3 of the tongue.
What is the glossopharyngeal nerve (CN 9) responsible for?
The glossopharyngeal nerve gives sensory innervation to the oropharynx and the anterior side of the epiglottis.
What role does the glossopharyngeal nerve play in the gag reflex?
The glossopharyngeal nerve is the afferent limb of the gag reflex.
What indicates inadequate anesthesia of the glossopharyngeal nerve during intubation?
If the patient gags during fiberoptic intubation, this indicates that the glossopharyngeal nerve was not adequately anesthetized.
What areas does the glossopharyngeal nerve innervate?
The glossopharyngeal nerve innervates the soft palate, oropharynx, tonsils, posterior 1/3 of the tongue, vallecula, and the anterior side of the epiglottis.
afferent limb of the gag reflex*
What does the vagus nerve (CN 10) innervate?
SLN-> internal (posterior epiglottis) and external (cricothyroid) SLN
RLN-> posterior epiglottis below cords/trachea and intrinsic m
What are the branches of the vagus nerve related to the larynx?
The superior laryngeal nerve (internal and external branches) and the recurrent laryngeal nerves.
What is the motor function of the internal branch of the superior laryngeal nerve?
0
What is the sensory function of the internal branch of the superior laryngeal nerve?
Posterior side of epiglottis to the level of vocal cords.
What is the motor function of the external branch of the superior laryngeal nerve?
Cricothyroid muscles (tense vocal cords).
What is the sensory function of the external branch of the superior laryngeal nerve?
0
What is the motor function of the recurrent laryngeal nerve?
All intrinsic laryngeal muscles EXCEPT cricothyroids.
What is the sensory function of the recurrent laryngeal nerve?
Below level of vocal cords to trachea.
What is the origin of the superior laryngeal nerve?
The superior laryngeal nerve branches off the vagus nerve just beyond the jugular foramen at the skull base.
At what level does the superior laryngeal nerve divide?
At the level of the hyoid, it divides into the internal and external branches.
Where does the internal branch of the superior laryngeal nerve penetrate?
The internal branch penetrates the thyrohyoid membrane between the greater cornu of the hyoid bone and the superior horn of the thyroid cartilage.
Where do the recurrent laryngeal nerves branch off?
The recurrent laryngeal nerves branch off the vagus inside the thorax.
How does the right recurrent laryngeal nerve travel?
The right RLN loops under the subclavian artery.
How does the left recurrent laryngeal nerve travel?
The left RLN loops under the aortic arch.
What is the path of both recurrent laryngeal nerves after looping under vascular structures?
Both nerves ascend the tracheoesophageal groove to join the larynx.
Why is the left recurrent laryngeal nerve more susceptible to injury?
Due to its location in the thorax, as it loops under the aortic arch.
What can cause RLN injury?
External pressure from ETT / LMA; Surgery: thyroid / parathyroid, Neck stretching, Neck tumor
What are the causes of RLN Injury on the left side?
PDA ligation, Left atrial enlargement (mitral stenosis), Aortic arch aneurysm, Thoracic tumor
What side of injury causes paralysis of the ipsilateral vocal cord abductors?
Unilateral injury causes paralysis of the ipsilateral vocal cord abductors.
What is a symptom of unilateral RLN injury?
This causes hoarseness, but it does not cause respiratory distress (it is not an emergency).
What is the most common nerve injury following subtotal thyroidectomy?
Unilateral RLN injury is the most common nerve injury following subtotal thyroidectomy.
What happens to the affected cord during inspiration in unilateral RLN injury?
The affected cord is drawn to midline during inspiration.
What causes bilateral paralysis of the vocal cord ABductors?
Bilateral injury causes bilateral paralysis of the vocal cord ABductors.
What does acute injury favor in vocal cord function?
Acute injury favors a dangerous situation where the tensing action of the cricothyroid muscles acts unopposed.
What are the symptoms of acute bilateral RLN injury?
This patient presents with stridor and respiratory distress (this is an emergency).
What is the treatment for acute bilateral RLN injury?
Treatment includes emergent intubation or a surgical airway and paralyze
How is chronic injury to the vocal cords typically tolerated?
Chronic injury is typically well tolerated.
What happens during inspiration with bilateral RLN injury?
Both cords are drawn to midline during inspiration, leading to airway obstruction.
Where should the needle be inserted for a glossopharyngeal nerve block?
At the base of the palatoglossal arch (anterior tonsillar pillar) to a depth of 0.25 - 0.5 cm.
What does aspiration of air indicate during glossopharyngeal nerve block?
The needle is too deep.
What should be done if blood is aspirated in glossopharyngeal nerve block?
Withdraw and redirect the needle medially, as the carotid artery is very close.
What is the recommended volume of local anesthetic to inject glossopharyngeal nerve block?
1-2 mL of local anesthetic, repeated on the contralateral side.
What is the incidence of intracarotid injection during the procedure?
There is a 5% incidence of intracarotid injection, which carries a risk of seizure.
Where is the anesthetic injected for a superior laryngeal nerve block?
At the inferior border of the greater cornu of the hyoid bone.
How much anesthetic is injected and where for superior laryngeal nerve block?
One mL is injected outside the thyrohyoid membrane, then 2 mL is injected 2-3 mm deep to the thyrohyoid membrane.
What should be done after injecting on one side for superior laryngeal nerve block?
Repeat the procedure on the contralateral side.
What does aspiration of air indicate during the procedure superior laryngeal nerve block?
It means that the needle is too deep.
What is the first step in a recurrent laryngeal nerve block using the transtracheal approach?
Puncture the cricothyroid membrane, and advance the needle in a caudal direction.
This reduces the risk of vocal cord injury.
What should be done after aspiration but before injection during transtracheal procedure?
Tell the patient to take a deep breath.
How much local anesthetic should be injected during inspiration transtracheal block?
Inject 3-5 mL of local anesthetic into the tracheal lumen.
What is the expected reaction of the patient after the injection? For transtracheal block
The patient will cough, spraying the local anesthetic upwards through the cords.
