Airway Anatomy and Physiology

81 Questions

What is the boundary of the oropharynx superiorly and inferiorly?

Superiorly by soft palate, inferiorly by epiglottis

Which of the following nasal sinuses is divided into posterior, middle, and anterior cells and consists of numerous air cells?

Ethmoid sinus

What is the function of the cricothyroid membrane?

Provides a site for emergency airway access

What is the only complete cartilaginous ring in the larynx?

Cricoid cartilage

Which of the following statements about the soft palate is true?

It rises when eating or drinking and prevents ingested substances from going to the nose

Which nerve is responsible for the motor function of all muscles of the larynx except the cricothyroid muscle?

Recurrent laryngeal nerve (RLN)

What is the function of the posterior cricoarytenoid muscle?

Abduction of the vocal cords

What is the site used for an emergency airway access?

Below the vocal cords

Where is the pituitary gland located in relation to the sphenoidal sinus?

Above the sphenoidal sinus in the sella turcica

What is the result of unilateral RLN injury?

Paralysis of the ipsilateral vocal cord, which compensates by shifting to the uninjured side

What is the function of an oral airway (OPA) device?

To resolve occlusion usually from the tongue or redundant tissue in the pharynx

Which nerve is responsible for the sensory function above the vocal cords?

Internal branch of the Superior laryngeal nerve (SLN)

What is the result of bilateral RLN injury?

Chronic bilateral RLN injury with gruff speech and increased risk of aspiration

Which of the following cartilages is NOT paired?

Epiglottis

What is the primary function of the arytenoid cartilage movement?

To allow for tension and relaxation of vocal cords

What is the response to noxious stimuli that causes vocal cord closure?

Laryngospasm

What is the function of the thyroepiglottic ligament?

To attach the epiglottis to the thyroid cartilage

What is the afferent limb of the gag reflex?

Glossopharyngeal nerve

What is the shape of the thyroid cartilage?

Shield-shaped

What is the location of the cuneiform cartilages?

Along the lateral edge of the arytenoids

Which of the following cartilages provides support for the aryepiglottic fold?

Corniculate and cuneiforms

Which of the following is the location of the vallecula?

On either side of the hypoepiglottic ligament

Which of the following cartilages attaches to the tongue at the base of the hyoid bone?

Epiglottis

Which of the following cartilages forms the laryngeal prominence?

Thyroid

Which of the following statements about the arytenoid cartilage is true?

It is a paired, flexible, pyramid-shaped cartilage

Which of the following nasal sinuses is the largest and only present at birth?

Maxillary sinus

At which level of the cervical spine is the oropharynx typically found?

C2-C3

What is the primary function of the soft palate?

Preventing ingested substances from going to the nose

Which of the following structures lies above the sphenoidal sinus in the sella turcica?

Pituitary gland

What is the typical drainage point of the maxillary and frontal sinus?

Middle nasal meatus

Which muscle is responsible for the abduction of the airway?

Posterior cricoarytenoid muscle

Which nerve is responsible for the sensory function below the vocal cords?

Recurrent laryngeal nerve

What is the result of acute bilateral RLN injury?

Unopposed tension and adduction of the vocal cords

Which muscle is responsible for the closure of the glottis?

Transverse arytenoid muscle

What is the efferent response of the gag reflex obtained via?

Vagus nerve

What is the location of the cricothyroid membrane?

Between the thyroid cartilage and the cricoid cartilage

What is the result of laryngospasm?

All of the above

What is the site used for an emergency airway access?

Cricothyroid membrane

An OPA opens the larynx

False

Laryngospasm may be provoked by airway instrumentation, pain, or visceral stimuli

True

During which stage of anesthesia is laryngospasm a concern?

Stage II Excitement/Delirium

What are the signs and symptoms of laryngospasm?

All of the above

What is the primary treatment for laryngospasm?

All of the above

At which point is the airway narrowest in infants and children? (select 2)

Cricoid cartilage

At what level is the airway narrowest in adults?

Vocal cords

Why is the epiglottis significant in infants?

It is longer, narrower, and stiffer in infants

SLN injury is associated with respiratory distress

False

Unilateral RLN injury can result in complete paralysis of vocal cords

False

What is a potential cause of left recurrent laryngeal nerve (RLN) injury?

Mitral stenosis

Is the soft palate capable of stretching and becoming more movable with age or obesity?

True

What is true about the hard palate?

It is immobile and covers the anterior portion of the oral cavity

What is the correct description of corniculate cartilages?

Paired conical nodules resting on the arytenoid apex

What is the function of Arytenoid cartilage movement in relation to vocal cords?

It allows for the tension and relaxation of vocal cords

What do the vocal cords attach to anteriorly and posteriorly?

Thyroid cartilage anteriorly and arytenoid cartilage posteriorly

What is the correct order of airway structures from pharynx to carina?

Pharynx → Larynx → Trachea → Carina→ Bronchi

Trachea is anterior to the esophagus

True

What is the correct range of the larynx?

From the epiglottis to the cricoid cartilage

The base of which cartilage articulates with and rotates on cricoid cartilage?

Arytenoid

What lies behind the tongue and forms the superior part of the anterior wall of the pharynx?

Epiglottis

Which laryngeal cartilage is located most anterior and cephalad of all others?

Epiglottis

What is attached to the internal surface of the thyroid cartilage and projects over the pharynx, allowing the passage of air into the larynx, trachea, and lungs?

Epiglottis

What cartilage has an inferior horn with a circular facet that allows it to articulate with the cricoid cartilage?

Thyroid cartilage

Which single cartilage lies mostly in the subglottic region?

Cricoid cartilage

What provides sensory innervation to the trachea?

Recurrent laryngeal nerve

What is the direction of the carina, which is the last tracheal cartilage?

Downward and backward

What is the function of extrinsic muscles in relation to the airway?

Provide gross motor movement to the larynx

What is the function of the intrinsic muscles in the airway?

Provide fine motor movement for sound production, phonation, and movement of vocal cords

What does abduction refer to in the context of airway anatomy?

Opening of the airway

What nerve provides innervation to all intrinsic muscles of the airway except the cricothyroid muscle?

RLN

All intrinsic muscles play a role in adduction of airway except posterior cricoarytenoid which abducts airway

True

What is true about the recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN)?

Both arise from branches of the vagus nerve

At what level of the spine does the Superior Laryngeal Nerve (SLN) arise from the vagus nerve?

At which point does the Superior Laryngeal Nerve (SLN) divide into internal and external branches?

Greater horn of hyoid bone

What muscle does the external branch of the superior laryngeal nerve (SLN) provide motor innervation to?

Cricothyroid muscle

What is unique about the recurrent laryngeal nerve (RLN)?

It is a branch of the vagus nerve that loops around the subclavian artery on the right side and the aortic arch on the left side

What is triggered by sensory receptors in the glottis and subglottic mucosa, resulting in strong adduction of the vocal cords?

Gag reflex

The efferent response of the gag reflex is obtained via which nerve?

Vagus nerve

Where does the gag reflex synapse?

Medulla with nuclei of vagus and spinal accessory nerves

What is the likely result of damage to the recurrent laryngeal nerve (RLN)?

Unopposed adduction, causing potential airway problems

What is the site used to perform a transtracheal block to anesthetize the recurrent laryngeal nerve (RLN)?

Cricothyroid membrane

What are the possible causes of recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN) injury?

All of the above

Study Notes

Nasal Sinuses

Ethmoid sinus: consists of numerous air cells, divided into posterior, middle, and anterior cells
Frontal sinus: lies in the frontal bone, drains into the middle nasal meatus
Maxillary sinus: largest sinus, present at birth, lies in maxilla on each side, drains into the middle nasal meatus
Sphenoidal sinus: contained within sphenoid bone, pituitary gland lies above in sella turcica

Oropharynx

Found at C2-C3 level
Bound superiorly by soft palate, inferiorly by epiglottis
Where we assess Mallampati classification
Hard palate: immobile/stationary, covers anterior portion of oral cavity
Soft palate:
- Covers posterior portion of oral cavity
- Rises when eating or drinking, preventing ingested substances from going to nose
- Can stretch and become more movable with age or obesity
Blood supply to mouth primarily from branches of the external carotid artery

Pharynx and Larynx

Pharynx and larynx are different structures
Larynx begins with the epiglottis and extends to the cricoid cartilage
OPA does not open the larynx, resolves occlusion usually from tongue or redundant tissue in pharynx

Cartilages of the Larynx

Paired: arytenoids, corniculates, cuneiforms
Arytenoids:
- Paired, flexible, pyramid-shaped cartilages
- Base articulates with and rotates on cricoid cartilage
- Vocal cords attach to arytenoid cartilages posteriorly and thyroid cartilages anteriorly
- Movement allows for tension and relaxation of vocal cords
Corniculate and cuneiforms:
- Corniculate cartilages are paired conical nodules resting on the arytenoid apex
- Cuneiform cartilages are paired cartilages that lie along the lateral edge of the arytenoids
- Both provide support for the aryepiglottic fold
Single: epiglottis, thyroid, cricoid (ETC)
Epiglottis:
- Curved leaf structure
- Located most anterior and cephalad of all laryngeal cartilages
- Lies behind tongue and forms superior part of the anterior wall of pharynx
- Attaches to tongue at the base of the hyoid bone and anteriorly by the hypoepiglottic ligament
- Extends down to the thyroid cartilage, attaching via the thyroepiglottic ligament
Thyroid cartilage:
- Shield-shaped and largest cartilage
- Forms the laryngeal prominence (Adam’s apple)
- Attaches to the inferior laryngeal constrictors, sternothyroid, and thyrohyoid muscles
- Inferior horn of thyroid cartilage has a circular facet that articulates with the cricoid cartilage
- Attached to the hyoid bone via the thyrohyoid ligament and the cricoid via the cricothyroid membrane
- Cricothyroid membrane is our emergency airway because it’s beneath the vocal cords
Cricoid cartilage:
- Single hyaline cartilage shaped like a ring
- Is the only complete cartilaginous ring
- Attaches to the thyroid cartilage and arytenoids
- Separated from the thyroid cartilage by the cricothyroid membrane
- Lies mostly in the subglottic region
Trachea:
- Tubular structure from cricoid cartilage to carina
- Anterior to esophagus
- Cricoid cartilage is the only cartilage of trachea that is a complete ring
- Sensory innervation is from the RLN
- Carina is downward and backward projection of last tracheal cartilage

Innervation of the Airway

Airway muscles:
- Extrinsic muscles: outside of the airway, provide gross motor movement to larynx
- Intrinsic muscles: inside of the airway, provide fine motor movement for sound production, phonation, and movement of vocal cords
- All intrinsic muscles innervated by RLN except the cricothyroid, which is innervated by SLN
- Abduction: opening of airway
- All intrinsic muscles play a role in adduction of airway except posterior cricoarytenoid, which abducts airway
Transverse arytenoid and oblique arytenoid close glottis
If there is damage to the RLN, there is unopposed adduction, causing potential airway problems

Cricothyrotomy and Emergency Airway

Site used as an emergency airway because it’s below the vocal cords
Attaches superior surface of cricoid cartilage to inferior edge of thyroid cartilage
Can be identified 1-1.5 fingerbreadths below the laryngeal prominence
Site used to perform transtracheal block to anesthetize the RLN

RLN and SLN Injury

Damage causes vocal cord dysfunction
Damage secondary to surgery, neoplasms, trauma
Unilateral RLN injury:
- Paralysis of the ipsilateral vocal cord
- Vocal cords compensate by shifting to the uninjured side
- Causes hoarseness
Left RLN injury can occur from mitral stenosis, dissecting aortic arch aneurysms
Bilateral RLN injury affects both vocal cords
- Chronic bilateral RLN injury – patients compensate but have gruff speech and increased risk of aspiration
- Acute bilateral RLN injury:
  - Causes unopposed tension and adduction of the vocal cords
  - Stridor → respiratory distress → death
SLN injury is not associated with respiratory distress

Laryngospasm

Laryngospasm: response to noxious stimuli causing vocal cords to close
Provoked by airway instrumentation/foreign body or vocal cord irritation
May also result from pain or visceral stimuli
Can cause partial or complete airway obstruction
Can cause hypoxia and NPEE (negative pressure pulmonary edema), dysrhythmias, cardiac arrest, and death
Concern in stage 2 (delirium/excitement) of general anesthesia
Afferent limb and efferent limb???
Inspiratory stridor
Suprasternal and subclavicular retraction during inspiration
Paradoxical appearance of chest wall
Treatment:
- Remove stimulus
- O2 and PPV
- Deepen anesthetic
- Bilateral pressure at laryngospasm notch (Larson’s maneuver)
- Neuromuscular blocking agent

Nasal Sinuses

Ethmoid sinus: consists of numerous air cells, divided into posterior, middle, and anterior cells
Frontal sinus: lies in the frontal bone, drains into the middle nasal meatus
Maxillary sinus: largest sinus, present at birth, lies in maxilla on each side, drains into the middle nasal meatus
Sphenoidal sinus: contained within sphenoid bone, pituitary gland lies above in sella turcica

Oropharynx

Found at C2-C3 level
Bound superiorly by soft palate, inferiorly by epiglottis
Where we assess Mallampati classification
Hard palate: immobile/stationary, covers anterior portion of oral cavity
Soft palate:
- Covers posterior portion of oral cavity
- Rises when eating or drinking, preventing ingested substances from going to nose
- Can stretch and become more movable with age or obesity
Blood supply to mouth primarily from branches of the external carotid artery

Pharynx and Larynx

Pharynx and larynx are different structures
Larynx begins with the epiglottis and extends to the cricoid cartilage
OPA does not open the larynx, resolves occlusion usually from tongue or redundant tissue in pharynx

Cartilages of the Larynx

Paired: arytenoids, corniculates, cuneiforms
Arytenoids:
- Paired, flexible, pyramid-shaped cartilages
- Base articulates with and rotates on cricoid cartilage
- Vocal cords attach to arytenoid cartilages posteriorly and thyroid cartilages anteriorly
- Movement allows for tension and relaxation of vocal cords
Corniculate and cuneiforms:
- Corniculate cartilages are paired conical nodules resting on the arytenoid apex
- Cuneiform cartilages are paired cartilages that lie along the lateral edge of the arytenoids
- Both provide support for the aryepiglottic fold
Single: epiglottis, thyroid, cricoid (ETC)
Epiglottis:
- Curved leaf structure
- Located most anterior and cephalad of all laryngeal cartilages
- Lies behind tongue and forms superior part of the anterior wall of pharynx
- Attaches to tongue at the base of the hyoid bone and anteriorly by the hypoepiglottic ligament
- Extends down to the thyroid cartilage, attaching via the thyroepiglottic ligament
Thyroid cartilage:
- Shield-shaped and largest cartilage
- Forms the laryngeal prominence (Adam’s apple)
- Attaches to the inferior laryngeal constrictors, sternothyroid, and thyrohyoid muscles
- Inferior horn of thyroid cartilage has a circular facet that articulates with the cricoid cartilage
- Attached to the hyoid bone via the thyrohyoid ligament and the cricoid via the cricothyroid membrane
- Cricothyroid membrane is our emergency airway because it’s beneath the vocal cords
Cricoid cartilage:
- Single hyaline cartilage shaped like a ring
- Is the only complete cartilaginous ring
- Attaches to the thyroid cartilage and arytenoids
- Separated from the thyroid cartilage by the cricothyroid membrane
- Lies mostly in the subglottic region
Trachea:
- Tubular structure from cricoid cartilage to carina
- Anterior to esophagus
- Cricoid cartilage is the only cartilage of trachea that is a complete ring
- Sensory innervation is from the RLN
- Carina is downward and backward projection of last tracheal cartilage

Innervation of the Airway

Airway muscles:
- Extrinsic muscles: outside of the airway, provide gross motor movement to larynx
- Intrinsic muscles: inside of the airway, provide fine motor movement for sound production, phonation, and movement of vocal cords
- All intrinsic muscles innervated by RLN except the cricothyroid, which is innervated by SLN
- Abduction: opening of airway
- All intrinsic muscles play a role in adduction of airway except posterior cricoarytenoid, which abducts airway
Transverse arytenoid and oblique arytenoid close glottis
If there is damage to the RLN, there is unopposed adduction, causing potential airway problems

Cricothyrotomy and Emergency Airway

Site used as an emergency airway because it’s below the vocal cords
Attaches superior surface of cricoid cartilage to inferior edge of thyroid cartilage
Can be identified 1-1.5 fingerbreadths below the laryngeal prominence
Site used to perform transtracheal block to anesthetize the RLN

RLN and SLN Injury

Damage causes vocal cord dysfunction
Damage secondary to surgery, neoplasms, trauma
Unilateral RLN injury:
- Paralysis of the ipsilateral vocal cord
- Vocal cords compensate by shifting to the uninjured side
- Causes hoarseness
Left RLN injury can occur from mitral stenosis, dissecting aortic arch aneurysms
Bilateral RLN injury affects both vocal cords
- Chronic bilateral RLN injury – patients compensate but have gruff speech and increased risk of aspiration
- Acute bilateral RLN injury:
  - Causes unopposed tension and adduction of the vocal cords
  - Stridor → respiratory distress → death
SLN injury is not associated with respiratory distress

Laryngospasm

Laryngospasm: response to noxious stimuli causing vocal cords to close
Provoked by airway instrumentation/foreign body or vocal cord irritation
May also result from pain or visceral stimuli
Can cause partial or complete airway obstruction
Can cause hypoxia and NPEE (negative pressure pulmonary edema), dysrhythmias, cardiac arrest, and death
Concern in stage 2 (delirium/excitement) of general anesthesia
Afferent limb and efferent limb???
Inspiratory stridor
Suprasternal and subclavicular retraction during inspiration
Paradoxical appearance of chest wall
Treatment:
- Remove stimulus
- O2 and PPV
- Deepen anesthetic
- Bilateral pressure at laryngospasm notch (Larson’s maneuver)
- Neuromuscular blocking agent

This quiz covers the anatomy and physiology of the airway, including the nasal sinuses, oropharynx, and related structures. Explore the details of the ethmoid, frontal, maxillary, and sphenoidal sinuses, as well as the oropharynx location and function.

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