Extrinsic Muscles of Larynx

Extrinsic Muscles of the Larynx: Groups and Functions

Two Main Groups:

Group	Location	Muscles Included	Function	Innervation
Suprahyoid	Superior to the hyoid bone	- Mylohyoid - Geniohyoid - Stylohyoid - Digastric (anterior & posterior bellies)	Elevate the hyoid and thus the larynx	- Mylohyoid & anterior digastric: Mandibular division of Trigeminal nerve (CN V3) - Stylohyoid & posterior digastric: Facial nerve (CN VII)
Infrahyoid	Inferior to the hyoid bone	- Sternohyoid - Thyrohyoid - Omohyoid - Sternothyroid - Thyrohyoid (mentioned twice, likely a reiteration)	Depress the hyoid and thus the larynx	Ventral rami of C1-C3 cervical nerves

 

 

Summary:

• Suprahyoid muscles pull the larynx upwards by elevating the hyoid.

• Infrahyoid muscles pull the larynx downwards by depressing the hyoid.

• Together, they contribute to laryngeal stability and influence pitch and voice intensity through positional adjustments of the larynx.

 How Extrinsic Muscles Affect Larynx Height and Pitch

Suprahyoid Muscles — Elevate Larynx → Increase Pitch

• When suprahyoid muscles contract, they raise the larynx.

• This increases tension on the conus elasticus (the elastic membrane lining the infraglottic cavity).

• Increased tension on the conus elasticus results in a higher pitch of the voice.

• Tension in suprahyoid muscles therefore correlates with higher vocal pitch.

 

Infrahyoid Muscles — Lower Larynx → Decrease Pitch

• When infrahyoid muscles contract, they lower the larynx.

• This reduces tension on the conus elasticus.

• Decreased tension causes a lower pitch.

• Contraction of infrahyoid muscles therefore correlates with lower vocal pitch.

 

Summary

• Larynx height adjustment by extrinsic muscles directly influences vocal pitch through tension changes in the conus elasticus.

• Suprahyoids raise and tense → higher pitch.

• Infrahyoids lower and relax → lower pitch.

Relation of Laryngeal Function to Sound Intensity

Sound Intensity Basics

• Sound intensity = energy used to produce sound.

• More energy → louder sound.

• Louder sound requires longer and stronger compression of the vocal folds.

• This compression depends on higher subglottic air pressure → faster airflow through the glottis.

 

Role of Conus Elasticus and Muscle Tension

• Increased tension on the conus elasticus (via suprahyoid muscle action) →

  • Greater vocal fold compression,

  • Higher subglottic pressure,

  • Increased airflow speed,

  • Resulting in higher volume (louder sound).

• However, this increased tension may also make pitch control more difficult due to stiffness.

 

Decreasing Volume

• To reduce volume, there is:

  • Shorter and weaker compression of vocal folds,

  • Lower subglottic pressure,

  • Reduced airflow speed,

  • Resulting in softer sound.

 

Clinical Application: Voice Hygiene

• Good voice hygiene helps control volume and pitch, avoiding excessive tension or strain on laryngeal structures.

• Prevents voice disorders caused by misuse of the extrinsic muscles affecting conus elasticus tension.

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