Larynx

The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3–C6 vertebrae. The larynx is continuous superiorly with the oropharynx and inferiorly with the trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea. This structure is made up of 9 cartilages that are connected by membranes, ligaments, and muscles and that house the vocal cords. The major structures forming the framework of the larynx are the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage, cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea, and prevents large molecules from reaching the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Table of Contents

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Development and Gross Anatomy

Development

  • The laryngeal cartilages develop from the 4th and 6th pairs of the pharyngeal arches Pharyngeal arches The branchial arches, also known as pharyngeal or visceral arches, are embryonic structures seen in the development of vertebrates that serve as precursors for many structures of the face, neck, and head. These arches are composed of a central core of mesoderm, which is covered externally by ectoderm and internally by endoderm. Branchial Apparatus and Aortic Arches.
  • The cricothyroid muscle originates from the 4th pharyngeal arch.
  • The rest of the intrinsic muscles of the larynx originate from the 6th pharyngeal arch.

Gross anatomy

The larynx is a framework composed mainly of cartilages held together by muscles and ligaments, both of which are divided into intrinsic and extrinsic forms.

Table: Gross anatomy
Cartilage Unpaired
  • Epiglottis
  • Cricoid
  • Thyroid
Paired
  • Arytenoid
  • Corniculate
  • Cuneiform
Ligaments Extrinsic
  • Thyrohyoid membrane
  • Hyoepiglottic ligament
Intrinsic
  • Cricothyroid ligament (also called cricovocal or cricothyroid membrane)
  • Vocal ligaments
  • Quadrangular membrane
  • Vestibular ligaments
  • Aryepiglottic membrane
Muscles Extrinsic
  • Suprahyoid group: stylohyoid, digastric, mylohyoid, and geniohyoid
  • Infrahyoid group: sternohyoid, omohyoid, sternothyroid, and thyrohyoid
Intrinsic
  • Cricothyroid
  • Thyroarytenoid
  • Posterior cricoarytenoid
  • Lateral cricoarytenoid
  • Transverse arytenoid
  • Oblique arytenoid
  • Vocalis
Anterior and right lateral views of the larynx

Anterior (top) and right lateral (bottom) views of the larynx, displaying its anatomical landmarks

Image: “Larynx” by OpenStax. License: CC BY 4.0

Joints of the larynx: 

  • Cricothyroid: allows forward and down tilting movement of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage between the inferior horns of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage and the cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage 
  • Cricoarytenoid: allows abduction and adduction of the vocal ligaments by means of the cricoid and arytenoid cartilages

Regions of the larynx:

  • Supraglottis: also called the vestibule, extends from the entrance of the larynx to the vestibular folds
  • Glottis: extends from the vestibular folds to the vocal folds
  • Subglottis: extends from the vocal folds to the lower margin of the cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage (beginning of the trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea)
Components and regions of the larynx

Components and regions of the larynx

Image by Lecturio.

Cartilages

Unpaired cartilages

  • Epiglottis:
    • Elastic cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
    • Leaf-shaped body
    • Entirely covered by mucosa
    • Projects superiorly and posteriorly into the pharynx Pharynx The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx and functions to close the larynx during swallowing to prevent food from entering the airway
    • Attaches to the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones superiorly via the hyoepiglottic ligament 
    • Attaches to the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage via the midline thyroepiglottic ligament 
  • Cricoid:
    • Hyaline cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
    • Ring-shaped body, making it the only complete ring of cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage in the larynx
    • Attaches to the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage via the cricothyroid ligament
    • Attaches to the 1st tracheal ring via the cricotracheal ligament
  • Thyroid:
    • The largest of the laryngeal cartilages
    • Hyaline cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
    • V-shaped body, with an anterior connection point and no posterior components
    • The anterior connection forms the laryngeal prominence, also known as the Adam’s apple.
    • The posterior aspects of the thyroid’s 2 lateral laminae project upward and downward, creating the superior (bigger) and inferior horns.
    • Attaches to the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones superiorly via the thyrohyoid membrane and median and lateral thyrohyoid ligaments
    • Attaches to the cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage inferiorly via the cricothyroid ligament

Paired cartilages

  • Arytenoid:
    • Hyaline cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
    • Pyramid-shaped bodies:
      • Superior apex
      • Anterior vocal process (site of attachment of the vocalis muscle)
      • Lateral muscular process
    • Located superiorly to the posterior portion of the cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage, between the lateral laminae of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
    • Attaches to the corniculate cartilages at their superior apexes
  • Corniculate:
    • Elastic cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
    • Cone-shaped bodies
    • Located superiorly, posteriorly, and medially to the arytenoids and serves to prolong them
    • Enclosed within the aryepiglottic folds of mucosa
  • Cuneiform:
    • Elastic cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
    • Club-shaped bodies
    • Located superiorly and anteriorly to the corniculate cartilages
    • Enclosed within the aryepiglottic folds of mucosa

Ligaments and Membranes

The ligaments and membranes of the larynx are responsible for connecting the cartilages and forming 1 single fibrocartilaginous structure. The membranes also fold over and enclose certain cartilages and membranes to comprise the moving and functional parts of the larynx (e.g., vocal cords).

Extrinsic

Thyrohyoid membrane:

  • Wide, fibrous sheet of tissue
  • Connects the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones to the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
  • Pierced by the internal laryngeal artery and the internal laryngeal nerve
  • Thickened areas comprise the single median thyrohyoid ligament and the two thinner and smaller thyrohyoid ligaments.

Hyoepiglottic ligament:

  • Thin, elastic tissue
  • Connects the anterior surface of the epiglottis to the upper border of the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones
  • Protects the supraglottic larynx
Lateral view of the larynx, featuring the membranes and cartilages

Lateral view of the larynx, featuring the membranes and cartilages

Image by Lecturio.

Intrinsic

Cricothyroid ligament:

  • Also called the cricovocal or cricothyroid membrane
  • Connects the lower border of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage to the upper border of the cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
  • Composed of the median and lateral cricothyroid ligaments:
    • Median: a thickened area at the anterior midline between the cartilages
    • Lateral: also known as the conus elasticus (elastic cone); thinner than the median ligament and extend from the superior border of the cricoid to the inferior border of the vocal ligaments, with which they are continuous
  • An incision is made through this structure during a cricothyrotomy to establish an emergency patent airway.

Vocal ligaments:

  • The free borders of the conus elasticus (lateral cricothyroid ligaments)
  • Extend from the vocal processes of the arytenoid cartilages to the angle of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage

Quadrangular membrane:

  • Thin, extends between the lateral borders of the epiglottis and the anterolateral margins of the arytenoid cartilages
  • Vestibular ligament:
    • The thick free lower edge of the quadrangular membrane
    • Enclosed in a fold of mucosa to form the vestibular folds (false vocal cords) that extend from the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage to the arytenoid cartilages
  • Aryepiglottic membrane:
    • The free upper edge of the quadrangular membrane
    • Enclosed in a fold of mucosa to form the aryepiglottic folds
    • Reinforced in its posterior portion by the corniculate and cuneiform cartilages, seen as small nodules within the fold
The ligaments and membranes of the larynx

The ligaments and membranes of the larynx

Image by Lecturio.

Muscles

Extrinsic laryngeal muscles

Suprahyoid group:

The suprahyoid laryngeal muscles are characterized by their location above the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones and function of elevating the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones and larynx during swallowing and phonation.

Table: Suprahyoid group
Muscle Origin Insertion Innervation
Stylohyoid Styloid process of the temporal bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones Body of the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones Facial nerve
Digastric Anterior belly: digastric fossa of the mandible Anterior and posterior bellies: intermediate tendon Anterior belly: mylohyoid nerve, branch of the mandibular nerve
Posterior belly: mastoid notch of the temporal bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones Posterior belly: facial nerve
Mylohyoid Mylohyoid line of mandible Body of the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones and median raphe Mylohyoid nerve, branch of the mandibular nerve
Geniohyoid Mental spine of the inner surface of the mandible Body of the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones C1–C2 of the cervical plexus and the hypoglossal nerve
The suprahyoid group of the extrinsic laryngeal muscles

The suprahyoid group of the extrinsic laryngeal muscles:
The geniohyoid muscle is not shown.

Image by BioDigital, edited by Lecturio

Infrahyoid group:

The infrahyoid laryngeal muscles are characterized by their location below the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones and by their function of depressing the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones and larynx during swallowing and phonation.

Table: Infrahyoid group
Muscle Origin Insertion Innervation
Sternohyoid Dorsal surface of the manubrium and the sternoclavicular joint Body of the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones C1–C3 of the cervical plexus
Omohyoid
  • Superior border of the scapula
  • Central tendon: deep cervical fascia (clavicle, 1st rib)
Body of the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones (connected to the carotid sheath)
Sternothyroid Dorsal surface of the manubrium Oblique line of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
Thyrohyoid (continuation of sternothyroid) Oblique line of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage Body and greater horns of the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones Hypoglossal nerve (cranial nerve XII), via the anterior rami of C1
Anterior and lateral views of the infrahyoid group of the extrinsic laryngeal muscles

Anterior and lateral views of the infrahyoid group of the extrinsic laryngeal muscles

Image by BioDigital, edited by Lecturio

Intrinsic laryngeal muscles

The intrinsic laryngeal muscles serve to produce phonation by modifying the length and tension of the vocal cords and the size of the rima glottidis (the opening between the vocal cords).

Table: Intrinsic laryngeal muscles
Muscle Origin Insertion Innervation
Cricothyroid Anterolateral portion of the cricoid
  • Oblique portion: inferior horn of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
  • Straight portion: inferior margin of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
External laryngeal nerve, branch of the superior laryngeal nerve
Thyroarytenoid Angle of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage and cricothyroid ligament Anterolateral surface of the arytenoids Inferior laryngeal nerve, branch of the recurrent laryngeal nerve
Posterior cricoarytenoid Posterior surface of the cricoid Muscular process of the arytenoids
Lateral cricoarytenoid Arch of the cricoid
Transverse arytenoid Lateral border and muscular process of the arytenoids Lateral border and muscular process of the opposite arytenoid
Oblique arytenoid Muscular process of the arytenoids Apex of the opposite arytenoid (with a prolongation to the aryepiglottic folds) Recurrent laryngeal nerve
Vocalis Lateral portions of the vocal processes of the arytenoids Anterior portion of the ipsilateral vocal ligament
  • Recurrent laryngeal nerve
  • External laryngeal nerve

Neurovasculature

Blood supply

  • Superior laryngeal artery:
    • Branch of the superior thyroid artery
    • Originates near the upper margin of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
    • Accompanies the internal branch of the superior laryngeal nerve
    • Supplies the internal surface of the larynx
  • Cricothyroid artery:
    • Branch of the superior thyroid artery 
    • Supplies the cricothyroid muscle
  • Inferior laryngeal artery:
    • Branch of the inferior thyroid artery
    • Accompanies the inferior laryngeal nerve
    • Supplies the mucous membranes and muscles in the inferior portion of the larynx

Venous drainage

  • Superior laryngeal vein:
  • Inferior laryngeal vein:
    • Joins the inferior thyroid vein
    • Drains into the brachiocephalic vein
Larynx blood supply and innervation

Larynx blood supply and innervation

Image by Lecturio.

Innervation

The innervation of the larynx is supplied by 2 branches of the vagus nerve: the superior and inferior laryngeal nerves.

Superior laryngeal nerve:

  • Originates from the inferior vagal ganglion
  • Divides into 2 branches:
    • Internal laryngeal nerve:
      • Sensory and autonomic
      • Larger of the 2 branches
      • Supplies sensory fibers to the mucous membranes in the laryngeal vestibule and middle laryngeal cavity and to the superior surface of vocal folds
    • External laryngeal nerve:
      • Motor
      • Smaller of the 2 branches
      • Innervates the pharyngeal constrictor and cricothyroid muscle

Inferior laryngeal nerve:

  • Constitutes the main motor nerve of the larynx
  • Continuation of the recurrent laryngeal nerve (branch of the vagus)
    • The left recurrent laryngeal nerve originates in the thorax.
    • The right recurrent laryngeal nerve originates in the root of neck.
  • Accompanies the inferior laryngeal artery
  • Divides into anterior and posterior branches
    • Anterior branch supplies the following muscles:
      • Lateral cricoarytenoid 
      • Thyroarytenoid
      • Vocalis
    • Posterior branch supplies the following muscles:
      • Posterior cricoarytenoid
      • Transverse and oblique arytenoids

Mnemonics:

  • “The larynx is supplied by the Xth (10th) cranial nerve.”
  • SCAR:
    • Superior laryngeal nerve innervates the Cricothyroid muscle.
    • All other muscles are innervated by the Recurrent laryngeal nerve.

Microscopic Anatomy

  • Larynx: mucous membrane containing ciliated columnar epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium (respiratory epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium)
  • Folds:
    • Vestibular cords (plicae vestibulares):
      • Stratified nonkeratinizing squamous epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium
      • Seromucous glands
    • Vocal cords (plicae vocales):
      • Stratified nonkeratinizing squamous 
      • No glands
      • Vocal ligament
      • Vocal muscle

Functions

Table: Functions of the larynx
Muscle Function
Cricothyroid
  • Forward and downward rotation of the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
  • Tautens and thins the vocal cords → production of higher-pitched sounds
Posterior cricoarytenoid
  • Abduction and external rotation of the arytenoid cartilages
  • Primary opener of the glottis
Lateral cricoarytenoid
  • Internal rotation of the arytenoid cartilages and adduction of the vocal cords
  • Closes the rima glottidis (“sphincter of the laryngeal inlet”)
  • Aids AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS in the production of whispered phonation
Transverse arytenoid
  • Adduction of the arytenoid cartilages
  • Closes the rima glottidis (“sphincter of the laryngeal inlet”)
Oblique arytenoid
  • Adduction of the arytenoid cartilages and the aryepiglottic folds
  • Closes the rima glottidis (“sphincter of the laryngeal inlet”)
Thyroarytenoid Sphincter of vestibule and laryngeal inlet
Vocal muscle Adjusts tension of the vocal folds

Movements of the larynx: 

Depending on the action (e.g., respiration, phonation, etc.), the laryngeal muscles regulate the movements of the vocal cords and determine the size of the rima glottidis, the opening between the vocal cords.

Table: Movements of the larynx
Movements
Respiration In quiet respiration:
  • Arytenoid cartilages are abducted.
  • Laryngeal inlet is open.
  • Rima glottidis is open and triangle-shaped.
In forced inspiration:
  • Arytenoid cartilages are rotated laterally.
  • Vocal folds are abducted.
  • Rima glottidis is open wider.
Phonation
  • Arytenoid cartilages and vocal folds are adducted.
  • Air is forced through rima glottidis.
Effort closure Rima glottidis is completely closed.
Swallowing
  • Laryngeal inlet is narrowed.
  • Rima glottidis is closed.
  • Larynx moves up and forward.
  • Epiglottis swings downward.
The functions of the intrinsic laryngeal muscles

The functions of the intrinsic laryngeal muscles:
Note the effects on the vocal cords and the rima glottidis.

Image by Lecturio.
Head and neck larynx and epiglottis

Intrinsic muscles of the larynx

Image by Lecturio.

Clinical Relevance

Infectious disorders of the larynx

  • Laryngitis Laryngitis Laryngitis is an inflammation of the larynx most commonly due to infection or trauma that can be either acute or chronic. In this condition, the 2 folds of mucous membranes that make up the vocal cords become inflamed and irritated. The inflammation results in a distortion of the voice produced, resulting in a hoarse sound or aphonia. Laryngitis: acute inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the larynx; can be infectious or noninfectious: Laryngitis Laryngitis Laryngitis is an inflammation of the larynx most commonly due to infection or trauma that can be either acute or chronic. In this condition, the 2 folds of mucous membranes that make up the vocal cords become inflamed and irritated. The inflammation results in a distortion of the voice produced, resulting in a hoarse sound or aphonia. Laryngitis results in fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, hoarseness, pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, or an irritating cough that worsens at night, along with a dry throat and malaise. Runny nose Nose The nose is the human body's primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Anatomy of the Nose and headache may be associated symptoms.
  • Epiglottitis Epiglottitis Epiglottitis (or "supraglottitis") is an inflammation of the epiglottis and adjacent supraglottic structures. The majority of cases are caused by bacterial infection. Symptoms are rapid in onset and severe. Epiglottitis: acute inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the epiglottis and surrounding structures in the supraglottic space: Epiglottitis Epiglottitis Epiglottitis (or "supraglottitis") is an inflammation of the epiglottis and adjacent supraglottic structures. The majority of cases are caused by bacterial infection. Symptoms are rapid in onset and severe. Epiglottitis is more life-threatening and sudden in onset than laryngitis. Haemophilus Haemophilus Haemophilus is a genus of Gram-negative coccobacilli, all of whose strains require at least 1 of 2 factors for growth (factor V [NAD] and factor X [heme]); therefore, it is most often isolated on chocolate agar, which can supply both factors. The pathogenic species are H. influenzae and H. ducreyi. Haemophilus influenzae is the culprit in children. Patients present with dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming "stuck." Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia and sore throat, along with dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea with or without stridor.
  • Diphtheria Diphtheria Diphtheria is an infectious disease caused by Corynebacterium diphtheriae that most often results in respiratory disease with membranous inflammation of the pharynx, sore throat, fever, swollen glands, and weakness. The hallmark sign is a sheet of thick, gray material covering the back of the throat. Diphtheria: serious bacterial infection caused by Corynebacterium Corynebacterium Corynebacteria are gram-positive, club-shaped bacilli. Corynebacteria are commonly isolated on tellurite or Loeffler's media and have characteristic metachromatic granules. The major pathogenic species is Corynebacterium diphtheriae, which causes a severe respiratory infection called diphtheria. Corynebacterium diphtheriae: Diphtheria Diphtheria Diphtheria is an infectious disease caused by Corynebacterium diphtheriae that most often results in respiratory disease with membranous inflammation of the pharynx, sore throat, fever, swollen glands, and weakness. The hallmark sign is a sheet of thick, gray material covering the back of the throat. Diphtheria affects the mucous membranes in the nose Nose The nose is the human body's primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Anatomy of the Nose and throat, resulting in sore throat, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, swollen glands, and weakness. 
  • Croup Croup Croup, also known as laryngotracheobronchitis, is a disease most commonly caused by a viral infection that leads to severe inflammation of the upper airway. It usually presents in children < 5 years of age. Patients develop a hoarse, "seal-like" barking cough and inspiratory stridor. Croup: Croup Croup Croup, also known as laryngotracheobronchitis, is a disease most commonly caused by a viral infection that leads to severe inflammation of the upper airway. It usually presents in children < 5 years of age. Patients develop a hoarse, "seal-like" barking cough and inspiratory stridor. Croup is a disease caused most commonly by a viral infection or rarely by a bacterial infection that results in swelling inside the trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea and interferes with normal breathing.

Congenital disorders of the larynx

Laryngomalacia Laryngomalacia Laryngomalacia and tracheomalacia are the most common upper airway conditions that produce stridor in newborns. Laryngomalacia and tracheomalacia tend to present in the 1st 2 weeks of life, with symptoms ranging from stridor to respiratory distress. The symptoms are caused by narrowing of the airway, which may be due to weakened cartilage, redundant tissue, external compression, or hypotonia of the affected area. Laryngomalacia and Tracheomalacia: excessive flaccidity of the supraglottic larynx leads it to be sucked out of position during inspiration, which can produce stridor: This condition manifests at birth and disappears after 2 years of age.

Miscellaneous disorders of the larynx

Foreign body aspiration Foreign body aspiration Foreign body aspiration can lead to choking and death by obstructing airflow at the larynx or trachea. Foreign bodies may also become lodged deeper in the bronchi; this may not affect breathing but can cause infection or erosion of bronchial walls. Foreign Body Aspiration: potentially life-threatening emergency that most commonly occurs in children ages 1–3 years. Presents as sudden onset of coughing, choking, stridor, and dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea.

References

  1. Drake, R., et al. Gray’s Anatomy for Students E-Book. Elsevier Health Sciences, 2014.
  2. Standring, S. Gray’s Anatomy: The Anatomical Basis of Clinical Practice, 41st ed. Edinburgh: Churchill Livingstone/Elsevier, 2016.

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