Anatomy 42 | Pharynx & Larynx

What is the path of air through the upper airway?

Air enters through the nasal or oral cavity, passes the nasopharynx or oropharynx, then moves to the laryngopharynx and into the larynx.

Functions of the larynx?

• Located below hyoid, above trachea, in front of esophagus

• Allows air from laryngopharynx to trachea

What cartilages make up the laryngeal skeleton?

• 3 unpaired: thyroid, cricoid, epiglottis

• 3 paired: arytenoids, corniculates, cuneiforms

• Total: 9 cartilages that support and protect the vocal cords

What are key features of the thyroid cartilage?

• Largest laryngeal cartilage, shield-shaped

• Forms laryngeal prominence “Adam’s apple”

• Connects to hyoid via thyrohyoid membrane

What are key features of the cricoid cartilage?

• Located below thyroid, above trachea

• Only complete ring of larynx or trachea

• Ring-shaped with broad lamina posteriorly, thin arch anteriorly

What are the functions of the epiglottis and arytenoid cartilages?

Epiglottis: Attached to the hyoid bone and thyroid cartilage; folds down to block the airway when you swallow.

Arytenoids: Rest on the cricoid cartilage; they rotate to open/close vocal cords and have small corniculate cartilages on top.

What are the key ligaments and membranes of the larynx?

• Vocal ligament: from arytenoid to thyroid cartilage, forms vocal cord

• Quadrangular membrane: spans epiglottis to arytenoid; lower edge is vestibular ligament

• Conus elasticus: connects cricoid cartilage to vocal ligament

What are vocal and vestibular folds?

• Vocal fold (true vocal cord): mucosa covering the vocal ligament

• Vestibular fold (false vocal cord): mucosa covering the vestibular ligament

• Aryepiglottic fold: superior edge of quadrangular membrane

What are the rima vestibuli and rima glottidis?

• Rima vestibuli: space between the vestibular folds

• Rima glottidis: space between the vocal folds

What are the key spaces of the larynx?

• Laryngeal inlet: opening from laryngopharynx to laryngeal vestibule

• Laryngeal vestibule: between inlet and vestibular folds

• Laryngeal ventricle: between vestibular and vocal folds

• Infraglottic space: between vocal folds and cricoid cartilage

What are the two main joints of the larynx and their functions?

• Cricothyroid joint: tilts thyroid cartilage forward, tightens vocal cords, raises pitch

• Cricoarytenoid joint: moves arytenoids to open/close vocal cords, adjusts rima glottidis size

What is the function and innervation of the cricothyroid muscle?

• Function: pulls thyroid cartilage forward, tightens vocal cords, raises pitch

• Innervation: external branch of the superior laryngeal nerve (only intrinsic laryngeal muscle not innervated by recurrent laryngeal nerve)

What are the actions and innervation of the intrinsic laryngeal muscles?

• Thyroarytenoid: shortens vocal folds, decreases tension

• Vocalis: fine-tunes vocal fold tension

• Transverse/Oblique arytenoids, Lateral cricoarytenoid: adduct vocal folds

• Posterior cricoarytenoid: abducts vocal folds

All are innervated by the inferior laryngeal nerve (branch of CN X).

What is the action and innervation of the thyroarytenoid muscle?

• Action: Pulls arytenoids forward to shorten vocal folds, lowering tension and pitch.

• Innervation: Inferior laryngeal nerve (branch of CN X).

What is the action and innervation of the vocalis muscle?

• Action: Fine-tunes vocal fold tension during speech and singing

• Innervation: Inferior laryngeal nerve (branch of CN X)

What is the action and innervation of the transverse and oblique arytenoid muscles?

• Action: Adduct vocal folds by pulling arytenoid cartilages together

• Innervation: Inferior laryngeal nerve (branch of CN X)

What is the action and innervation of the lateral cricoarytenoid muscles?

• Action: Adduct vocal folds by rotating arytenoids medially

• Innervation: Inferior laryngeal nerve (branch of CN X)

What is the action and innervation of the posterior cricoarytenoid muscles?

• Action: Abduct vocal folds; only muscle that opens rima glottidis

• Innervation: Inferior laryngeal nerve (branch of CN X)

How do laryngeal muscles contribute to respiration and speech?

• Forced respiration: Posterior cricoarytenoids abduct vocal folds

• Phonation: Adducted vocal folds vibrate to produce tone

• Whispering: Vocal folds adduct, but arytenoids stay apart to allow airflow without tone

What nerves provide sensory innervation to the larynx above and below the vocal folds?

• Above vocal folds (including them): Internal branch of superior laryngeal nerve

• Below vocal folds: Inferior laryngeal nerve

What are the motor and sensory roles of the laryngeal nerves derived from CN X (vagus)?

• External branch of superior laryngeal nerve: motor to cricothyroid

• Internal branch of superior laryngeal nerve: sensory above vocal folds

• Inferior laryngeal nerve: motor to all other intrinsic muscles, sensory below vocal folds

What is the relationship between the recurrent and inferior laryngeal nerves?

The inferior laryngeal nerve is the continuation of the recurrent laryngeal nerve after it passes the cricothyroid joint.

What is the clinical importance of the piriform recess?

Food or pills can lodge here after swallowing; internal and inferior laryngeal nerves lie deep to its mucosa and are at risk if injured.

What are the laryngeal arteries and what do they accompany?

The superior laryngeal artery (from external carotid) enters via the thyrohyoid membrane with the internal branch of the superior laryngeal nerve.

The inferior laryngeal artery (from subclavian) enters with the recurrent laryngeal nerve.

How does lymph from the larynx drain based on the vocal fold level?

• Above the vocal folds, lymph drains through the thyrohyoid membrane to superior deep cervical lymph nodes.

• Below the vocal folds, lymph drains into pretracheal/paratracheal nodes, then to inferior deep cervical lymph nodes.

A 30-year-old female undergoes a biopsy of the thyroid gland. During the procedure, the recurrent laryngeal nerve was damaged. This injury would most likely cause the sensory innervation in which location to be diminished?

• Infraglottic space

• Laryngeal inlet

• Laryngeal ventricle

• Laryngopharynx

• Vestibular fold

Infraglottic space

The recurrent laryngeal nerve is responsible for:

• Motor innervation to most of the intrinsic muscles of the larynx (except the cricothyroid).

• Sensory innervation to the infraglottic space, which is the area below the vocal cords.

Damage to this nerve, such as during a thyroid biopsy, would diminish sensation in the infraglottic space.

The muscle indicated by the arrow has which primary action on the vocal folds?

• Abduction

• Adduction

• Decreasing tension

• Increasing tension

• Minute changes in tension

Abduction (posterior cricoarytenoid)

The posterior cricoarytenoid muscle is the only muscle that abducts the vocal folds, meaning it opens the glottis (space between the vocal cords).

It’s important for breathing, as it allows air to pass through the larynx.

Which structure enters the larynx by piercing the structure indicated by the arrow?

• External branch of superior laryngeal nerve

• Recurrent laryngeal nerve

• Inferior laryngeal artery

• Superior laryngeal artery

• Superior thyroid artery

Superior laryngeal artery

The arrow points to the thyrohyoid membrane. The superior laryngeal artery, along with the internal branch of the superior laryngeal nerve, pierces this membrane to enter the larynx.

Identify the structure indicated by the tip of the arrow.

• Choana

• Eustachian tube

• Salpingopharyngeal fold

• Sphenoethmoidal recess

• Torus tubarius

Torus tubarius