Embryology, Anatomy, and Histology of the Larynx and Trachea

Superior border:

• Tip of epiglottis

Inferior border:

• Inferior rim of the cricoid cartilage

Anterior border:

• Lingual surface of epiglottis (vallecula), thyrohyoid membrane, anterior commissure, thyroid cartilage, cricothyroid membrane, and the anterior arch of the cricoid

Posterior border:

• Posterior commissure, arytenoid and interarytenoid space, and the mucoperichondrium overlying the cricoid cartilage

Lateral border:

• Aryepiglottic folds

Supraglottis:

• Extends from the tip of the epiglottis to a horizontal line passing through the apex of the ventricle

• Structures in this compartment include:

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    Epiglottis (lingual and laryngeal aspects), aryepiglottic folds, arytenoids, false vocal cords, and ventricle

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    Supraglottic larynx arises from the third and fourth branchial arches.

Glottis:

• Extends from the ventricle to approximately 0.5 to 1.0 cm below the free level of the true vocal cord and includes the anterior and posterior commissures and the true vocal cord:

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    Glottic portion of the larynx arises from the sixth branchial arch.

Subglottis:

• Extends from approximately 0.5 to 1.0 cm below the level of the true vocal cord to the inferior rim of the cricoid cartilage:

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    Subglottic larynx arises from the sixth branchial arch.

Paralumenal spaces

• Represent potential spaces that lie between the laryngeal cartilages and ligaments and membranes that support them

• Three main paralumenal spaces include:

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    Pre-epiglottic space

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    Paraglottic space

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    Subglottic space

Pre-epiglottic space:

• Not a space but represents a roughly triangular area lying anterior to the epiglottic cartilage that is filled with adipose tissue and loose connective tissue bounded:

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    Anteriorly by hyoid bone, thyroid cartilage, and thyrohyoid membrane

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    Posteriorly by epiglottic cartilage and thyrohyoid ligament

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    Superiorly by hypoepiglottic ligament forming the base

• Contains lymphatics and blood vessels but no lymph nodes

• Malignancies of laryngeal surface of the epiglottis may invade fat and areolar tissue of pre-epiglottic space.

Paraglottic space:

• Not a space but represents an area deep to the true and false vocal cords that contains adipose tissue and loose connective tissue bounded:

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    Inferiorly by conus elasticus (i.e., cricovocal membrane)

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    Laterally by thyroid cartilage

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    Medially by quadrangular membrane

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    Posteriorly by piriform sinus

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    Superiorly is in continuity with pre-epiglottic space

• Contains lymphatics and blood vessels but no lymph nodes

• Supraglottic tumors may spread into paraglottic space and reach the subglottis or extend beyond the limits of the larynx.

• Fixation of vocal cord represents good indicator of a tumor in the paraglottic space

Subglottic space:

• Bounded:

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    Laterally by conus elasticus (i.e., cricovocal membrane)

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    Medially by mucosa of subglottic region

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    Superiorly by undersurface of Broyle's ligament

• Continuous with inner surface of cricoid cartilage and its mucosa

• Broyle's ligament:

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    Site where vocal fold meets anteriorly (known as anterior commissure) and is region where fibers of vocal ligament pass through thyroid cartilage to blend with overlying perichondrium forming Broyle's ligament

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    Broyle's ligament contains blood vessels and lymphatics, representing potential route for escape of malignant tumors of the larynx.

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    Laryngeal cartilage ( Fig. 14-6 )

    

Skeleton of larynx composed of cartilage, fibrous sheets, and bands; attached muscles adjust position of cartilages, changing shape and tension of vocal cords

Thyroid cartilage:

• Largest of the laryngeal cartilage

• Double-winged

Cricoid cartilage:

• Only complete ring in respiratory system

• Represents foundation of larynx

• Resembles signet ring with larger part facing posteriorly

Arytenoid cartilage:

• Paired cartilage perched on superior edge of cricoid cartilage

• Each cartilage is pyramidal.

• At inferior aspect are two projections:

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    Muscular process on posterolateral margin

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    Vocal process located anteriorly

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      Vocal ligament attaches to vocal process of arytenoid cartilage.

• Superior process represents apex of pyramid:

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    Corniculate cartilage rests on the margin of the superior process of the arytenoid cartilage.

• Articulations between the various laryngeal joints are synovial and may be involved by an arthritic process.