Larynx

Laryngeal Structure Review

🦴 Key Anatomical Structures Covered

🧠 Relations to Adjacent Structures

• Pharynx – posterior to the larynx

• Hyoid bone – superior support structure

• Trachea – inferior continuation of the airway

• Thyroid gland – lies anterior and lateral to the larynx

• Major neurovascular bundles of the neck – crucial for innervation and blood supply

🛠 Principal Laryngeal Cartilages

• Epiglottis – elastic cartilage for airway protection during swallowing

• Thyroid cartilage – largest cartilage, forms the "Adam's apple"

• Cricoid cartilage – complete ring, foundation of the larynx

• Arytenoid cartilages – paired, pivotal for vocal fold movement

 

🧵 Vocal Fold Anatomy

• True vocal folds – involved in sound production

• False vocal folds (vestibular folds) – protective function

• Membranous connections:

  • Quadrangular membrane (above) connects to false folds

  • Conus elasticus (below) connects to true folds

 

🔄 Laryngeal Joints

• Cricothyroid joint

  • Histology: synovial

  • Function: tilts thyroid cartilage to adjust pitch

• Cricoarytenoid joint

  • Histology: synovial

  • Function: adducts and abducts vocal folds (phonation and respiration)

 

📌 Clinical Relevance to Robert

• Understanding the anatomy, histology, and movement of these structures is essential for:

  • Interpreting Robert’s voice difficulties

  • Assessing possible structural or neuromuscular dysfunctions

  • Planning targeted therapy or intervention strategies

 Structure and Function of the Larynx

🧱 Structural Overview

• The larynx is a musculo-cartilaginous structure.

• It is located between the laryngeal inlet (superiorly) and the trachea (inferiorly).

• Composed of cartilage, muscle, ligaments, and membranes, it maintains airway patency and enables movement required for voice and airway protection.

 

🌬 Primary Function: Airway Management

• Air Passageway: Allows air to travel from the pharynx to the trachea and lungs.

• Airway Closure:

  • The glottis (space between the vocal folds) functions as a sphincter.

  • Can close tightly to:

    • Prevent aspiration (protect the lower airway)

    • Clear the upper airway (via coughing)

    • Assist in abdominal straining (e.g. lifting, defecation, childbirth)

 

🎤 Special Function: Phonation

• Exhaled air from the lungs causes the true vocal folds to vibrate.

• This vibration generates sound, which is shaped by the supralaryngeal structures (e.g. oral and nasal cavities) to produce speech.

• Voice quality depends on the health, position, and coordination of the vocal folds.

 

📌 Clinical Link to Robert

• Understanding these functions is crucial when evaluating voice disorders in children like Robert.

• Issues may relate to:

  • Incomplete closure (leading to breathy or weak voice)

  • Tension abnormalities (impacting pitch or loudness)

  • Neuromuscular control affecting fold vibration and closure

Anatomical Relationships of the Larynx

📌 Position Overview

The larynx is centrally located in the anterior neck and is surrounded by several key anatomical structures:

 

🔄 Spatial Relationships

• Anterior (in front):

  • Skin

  • Subcutaneous tissue

  • Strap muscles of the neck (e.g. infrahyoid muscles)

• Posterior (behind):

  • Laryngopharynx (also called the hypopharynx)

    • Critical for swallowing; lies directly behind the larynx

• Superior (above):

  • Hyoid bone

    • Suspends the larynx

    • Forms part of the upper boundary of the airway

    • Will be discussed in detail in a later section

• Inferior (below):

  • Trachea

    • Continuation of the airway

  • Thyroid gland

    • Lies anterior and lateral to the upper trachea and larynx

    • Important in relation to surgical procedures and voice changes

• Lateral (to each side):

  • Major neurovascular bundles of the neck, including:

    • Common carotid artery

    • Internal jugular vein

    • Vagus nerve (CN X) — crucial for laryngeal innervation

 

📍 Relevance to Robert

• These relationships are important when considering causes of voice issues, such as:

  • Compression, inflammation, or pathology involving adjacent structures (e.g. thyroid gland)

  • Nerve involvement, especially recurrent laryngeal or superior laryngeal nerve damage

Neurovascular Bundles in Context of the Larynx

🩻 Anatomical Diagram Reference

• When viewing a median visceral column cross-section of the neck, we see paired neurovascular bundles on either side of the larynx and trachea.

 

🔀 Key Components of the Neurovascular Bundles

• Common Carotid Artery

  • Major artery supplying head and neck

  • Located medial in the bundle

  • Bifurcates into internal and external carotid arteries around the level of the thyroid cartilage

• Internal Jugular Vein

  • Major venous drainage from the brain and superficial face

  • Positioned lateral to the common carotid artery

• Vagus Nerve (Cranial Nerve X)

  • Sits between and slightly posterior to the artery and vein

  • Crucial for parasympathetic control and laryngeal innervation

 

🔌 Laryngeal Innervation by the Vagus Nerve

• Superior Laryngeal Nerve (branch of CN X)

  • External branch: motor to cricothyroid muscle (pitch control)

  • Internal branch: sensory to supraglottic larynx

• Recurrent Laryngeal Nerve

  • Loops around major arteries (aortic arch on left, subclavian on right)

  • Ascends in the tracheoesophageal groove

  • Motor to all intrinsic laryngeal muscles (except cricothyroid)

  • Sensory to infraglottic larynx

 

🧒 Relevance to Robert’s Voice Disorder

• Any compression, inflammation, or injury to these neurovascular structures can affect laryngeal nerve function, leading to:

  • Weak voice or dysphonia

  • Impaired pitch modulation

  • Aspiration risk if sensory nerves are affected

Structure of the Larynx: "Tube Within a Tube" Concept

🧊 Outer Tube: The Laryngeal Skeleton

• Function: Provides shape, support, and protection

• Composed of:

  • Cartilages (e.g. thyroid, cricoid, arytenoid, epiglottis)

  • Fibrous membranes connecting the cartilages

• This outer tube forms an incomplete skeleton, open posteriorly in some regions (e.g. thyroid cartilage).

 

🧵 Inner Tube: The Functional Core

• Lies within the cartilaginous framework and comprises key structures involved in voice and airway protection:
  🦴 Ligaments and Intrinsic Membranes

  • Provide structural integrity and movement pathways

  • Anchor the vocal folds and shape the glottis
    🧫 Lining and Epithelium

  • Lined with mucosa, which is:

    • Stratified squamous epithelium over areas of high mechanical stress (e.g. vocal folds, epiglottis)

    • Ciliated pseudostratified epithelium in lower-resistance regions (e.g. subglottis)

  • Mucosa is vital for hydration, protection, and vocal fold vibration

 

🎯 Functional Significance

• This dual-tube structure:

  • Maintains structural flexibility and movement capacity

  • Supports fine control of airflow and vocal fold tension

  • Allows for phonation, breath control, and airway protection

 

👶 Clinical Relevance to Robert

• Disruption in any layer (e.g. cartilage, membranes, mucosa) may affect:

  • Voice quality

  • Airway patency

  • Sensitivity of the larynx, impacting protective reflexes and phonation

Cartilages of the Larynx and Their Connections

 

🔢 Three Unpaired Cartilages

These form the midline framework of the larynx and serve as anchors for ligaments, membranes, and muscles.

 

1. Epiglottis

• Type: Elastic cartilage

• Function: Folds down during swallowing to protect the airway

• Shape: Leaf-like, attached to the inner surface of the thyroid cartilage

• Clinical note: Elastic cartilage resists calcification with age, maintaining flexibility

 

2. Thyroid Cartilage

• Type: Hyaline cartilage

• Structure:

  • Laryngeal prominence (Adam’s apple) — anterior bulge

  • Superior horns — connect to the hyoid bone

  • Inferior horns — articulate with cricoid cartilage

• Function: Largest laryngeal cartilage; houses the vocal folds on its internal surface

• Muscle and ligament connections:

  • Thyrohyoid membrane (to hyoid)

  • Cricothyroid membrane (to cricoid)

 

3. Cricoid Cartilage

• Type: Hyaline cartilage

• Shape: Signet ring — broad posteriorly, narrow anteriorly

• Position: Lies below the thyroid cartilage and above the trachea

• Key connection:

  • Cricothyroid membrane (joins anterior part of cricoid to thyroid cartilage)

• Articulates with:

  • Thyroid cartilage (at cricothyroid joint)

  • Arytenoid cartilages (posterior surface)

 

🧠 Why Names Matter

• Many ligaments, membranes, and muscles are named after the cartilages they connect or act upon:

  • Cricothyroid membrane

  • Thyroepiglottic ligament

  • Cricothyroid muscle

 

👶 Relevance to Robert’s Case

• Structural or developmental issues in these cartilages or their associated joints and membranes could:

  • Affect vocal fold positioning or tension

  • Impair voice production or airway protection

Paired Cartilages of the Larynx

🔢 Three Paired Cartilages

These six smaller cartilages (in three bilateral pairs) are crucial for vocal fold movement, support, and structure within the laryngeal inlet.

 

1. Arytenoid Cartilages 🔄

• Type: Hyaline cartilage

• Shape: Pyramidal (three-sided)

• Position: Sit on top of the posterior cricoid cartilage

• Function:

  • Anchor the posterior ends of the true vocal folds

  • Enable movement of the vocal folds through rotation and gliding

• Muscle attachments:

  • Posterior cricoarytenoid (abducts vocal folds)

  • Lateral cricoarytenoid (adducts vocal folds)

  • Arytenoid muscles (assist in adduction)

 

2. Corniculate Cartilages 🌽

• Type: Elastic cartilage

• Position: Sit atop the arytenoids

• Function:

  • Provide structural support to the aryepiglottic folds

  • Covered by mucosa — not directly visible

• Lined by: Stratified squamous epithelium within the aryepiglottic fold

 

3. Cuneiform Cartilages 🌀

• Type: Elastic cartilage

• Position: Embedded within the aryepiglottic folds, anterior to corniculate cartilages

• Function:

  • Provide support and stiffness to the aryepiglottic fold

  • Help maintain the opening of the laryngeal inlet

• Lined by: Mucosa with stratified squamous epithelium

 

🧒 Clinical Relevance to Robert

• Arytenoid dysfunction may lead to:

  • Poor vocal fold closure

  • Breathy, weak, or hoarse voice

• Corniculate and cuneiform abnormalities are rare but may cause:

  • Laryngeal inlet collapse

  • Inspiratory stridor or airway resistance during breathing

True vs False Vocal Folds

🧩 Overview of the Folds

The vocal folds (cords) are key components of the larynx. They are divided into false (vestibular) and true folds, each with distinct locations, structures, and functions.

 

🔹 False Vocal Folds (Vestibular Folds)

• Location: Superior to the true vocal folds

• Function:

  • Protective — help close the airway during swallowing

  • Not involved in normal phonation (sound production)

• Structure:

  • Composed of mucosa and vestibular ligament

  • Contain few muscle fibres

• Why “Vestibular”?

  • “Vestibule” refers to an entrance — these folds form the roof of the laryngeal vestibule, guarding the airway entrance

• Clinical note: Can contribute to ventricular phonation (a voice disorder where false folds are used to compensate)

 

🔸 True Vocal Folds

• Location: Inferior to the false vocal folds

• Function:

  • Voice production (phonation)

  • Contribute to airway protection and control

• Attachments:

  • Posteriorly to the arytenoid cartilages

  • Anteriorly to the inner surface of the thyroid cartilage (at the midline)

• Structure:

  • Formed by the vocal ligament and vocalis muscle (part of thyroarytenoid)

  • Covered by stratified squamous epithelium (due to mechanical stress)

• Highly dynamic: Tension, length, and position change with voice and breathing

 

🔳 Glottis

• Definition: The space between the true vocal folds

• Function:

  • Opens (abducts) during breathing

  • Closes (adducts) during phonation or protective reflexes (e.g. coughing)

• Importance: Acts as a sphincter to protect lower airways and control vocal tone

 

👶 Relevance to Robert

• Voice issues in children often involve the true vocal folds — e.g. nodules, poor closure, or misuse

• Observation of glottic behaviour can reveal key pathologies (e.g. incomplete closure, asymmetry, or tension abnormalities)

 Three Regions of the Larynx

Understanding the division of the larynx is essential for identifying the location of lesions, voice pathologies, and functional roles of each region — especially in the context of paediatric voice disorders like Robert's.

 

1⃣ Supraglottic Cavity (Vestibule)

• Location: Above the glottis (superior to the true vocal folds)

• Boundaries:

  • Superior: Laryngeal inlet

  • Inferior: Vestibular (false vocal) folds

• Contents:

  • Epiglottis

  • False vocal folds (vestibular folds)

  • Aryepiglottic folds

• Function:

  • Assists in airway protection

  • Redirects food away from glottis during swallowing

• Epithelium: Mostly respiratory epithelium (except areas under mechanical stress)

 

2⃣ Glottis

• Location: Middle part of the larynx

• Includes:

  • True vocal folds

  • Rima glottidis — space between the folds

• Function:

  • Voice production

  • Sphincteric protection during swallowing and coughing

• Highly dynamic: Width and tension adjust during phonation, respiration, and effort closure

 

3⃣ Infraglottic Cavity

• Location: Below the glottis, extending to the lower border of the cricoid cartilage

• Boundaries:

  • Superior: Lower edge of true vocal folds

  • Inferior: Continues into the trachea

• Contents:

  • Lined by conus elasticus (a key fibroelastic structure)

• Function:

  • Supports the vibratory mechanism of the vocal folds from below

  • Forms part of the cricovocal membrane, contributing to the vocal ligament

  • Conducts air to and from the trachea

 

⚙ Conus Elasticus (Lateral Cricothyroid Ligament)

• Structure:

  • Shaped like an inverted cone

  • Extends from the cricoid cartilage upward to the vocal ligaments

• Function:

  • Helps form the true vocal folds

  • Provides tensile strength and recoil properties for vibration

  • Integral to phonation mechanics

 

👶 Clinical Link to Robert

• Pathology in the supraglottic or infraglottic areas (e.g. inflammation, mass lesions, malformations) can:

  • Impede airflow

  • Alter voice quality

  • Influence resonance or pitch

Intrinsic Ligaments of the Larynx & Their Functional Significance

The intrinsic ligaments of the larynx form a critical part of the inner lining of the “tube within a tube” structure. These ligaments give rise to the true and false vocal folds, and their elasticity and tension are key to voice production and airway protection.

 

🔹 1. Quadrangular Membrane

• Location: Lines the supraglottic cavity

• Extent: From the lateral edges of the epiglottis to the arytenoid cartilages

• Lower border:

  • Thickens to form the vestibular ligament

  • This ligament is covered by mucosa to become the false vocal fold (vestibular fold)

• Function:

  • Helps seal the supraglottic airway during swallowing

  • Structural support for the upper larynx

  • Not involved in phonation

 

🔸 2. Conus Elasticus (Cricovocal Membrane)

• Location: Lines the infraglottic cavity (below the glottis)

• Structure: A cone-shaped fibroelastic sheet extending from:

  • Superiorly: Vocal ligaments (true vocal folds)

  • Inferiorly: Upper border of the cricoid cartilage

• Upper border:

  • Thickened to form the vocal ligament

  • This ligament is covered by stratified squamous epithelium and forms the true vocal fold

• Contains: Elastic tissue — enabling stretch and recoil

 

📢 Functional Importance of Elasticity

• Conus elasticus = key player in phonation:

  • Its elastic properties allow the vocal folds to:

    • Stretch to modulate pitch

    • Tense to generate subglottic pressure

    • Vibrate efficiently for sound production

• Greater elasticity = better pressure regulation:

  • Especially for increasing loudness (higher subglottic pressure)

 

👶 Relevance to Robert

• The development or pathology of the conus elasticus or quadrangular membrane can:

  • Affect voice quality (e.g. breathiness, weakness)

  • Limit loudness or vocal projection

  • Impact vocal fold tension (e.g. in paediatric voice misuse or congenital abnormalities)

Joints of the Larynx

1⃣ Cricoarytenoid Joints

• Location: Between the cricoid cartilage and the arytenoid cartilages

• Type: Synovial pivot joints

• Movements allowed:

  • Rotation

  • Sliding (gliding)

  • Tilting

• Functional significance:

  • Control the position and tension of the vocal ligaments (true vocal folds)

  • Enable abduction (opening) and adduction (closing) of the vocal folds during breathing and phonation

• Clinical note: Dysfunction can cause vocal fold paralysis or immobility, affecting voice and airway protection

 

2⃣ Cricothyroid Joints

• Location: Between the thyroid cartilage and the cricoid cartilage

• Type: Synovial plane joints

• Movements allowed:

  • Rocking (tilting) forward and backward of the thyroid cartilage

• Functional significance:

  • Adjusts tension and length of the vocal ligaments

  • Primarily responsible for pitch modulation (higher pitch by increasing tension)

• Clinical note: Impairment can result in monotone voice or difficulty adjusting pitch

 

🙏 Conclusion

• These joints are essential for the fine motor control of voice production and airway protection.

• Their synovial nature allows for smooth, flexible movements required for dynamic vocal fold positioning.