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Laryngeal Anatomy

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Extrinsic Laryngeal Muscles• Three Main Purposes:

1) Fixation (primary role)2) Elevation (move larynx up)3) Depression (move larynx down)

• Two major groups of extrinsic musclesSuprahyoid & Infrahyoid

• Anatomical position: Suprahyoid- one of the above attachments lies above the larynx.Infrahyoid- one of the attachments lies

below the larynx.

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Extrinsic Laryngeal Muscles• Suprahyoid Muscles:

1) Digastric2) Geniohyoid3) Hyoglossus4) Mylohyoid5) Stylohyoid

• Function: Raise the hyoid bone & indirectly raise the larynx.

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Digastric

• Two fleshy bellies

• Anterior belly- originates from the inside surface of the lower border of the mandible near the symphysis and inserts into the lesser horn of the hyoid bone

• Posterior belly- Originate from the mastoid process of the temporal bone to the sternocleidomastoid muscle

• Two bellies meet and are joined by an intermediate tendon

• Contraction raises hyoid or if hyoid is fixed, may assist in depressing lower jaw

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Stylohyoid

• Superficial to the diagastric

• Originates from posterior and lateral surface

of the styloid process of the temporal bone &

inserts into hyoid bone

• Contraction draws the hyoid bone up and

backward

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Mylohyoid

• Forms muscular floor of mouth

• Originate from the mylohyoid line (inner surface of mandible)

• Fibers coarse medially and downward and join the other paired muscle at the raphe

• Posterior fibers attach right to hyoid bone

• Contraction elevates the hyoid, floor of mouth and tongue

• Hyoid fixed, may assist in depressing mandible

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Geniohyoid

• Paired, cylindrical muscle located above the

superior surface of the mylohyoid muscle

• Originate by means of a short tendon, from

the lower part of the mental symphysis

• Insert into anterior surface of the hyoid

• Mandible fixed, this muscle pulls the hyoid

bone up and forward

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Hyoglossus

• Extrinsic muscle of the tongue

• Influences position of the larynx

• Arises from upper border of the body and greater horns of the hyoid bone

• Inserts into posterior and lateral regions of the tongue

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Genioglossus

• Extrinsic tongue muscle which influences position of the larynx

• Originates from the mental symphysis

• Fibers fan out and course toward their insertion

• Lower fibers insert into the body of the hyoid bone

• Upper fibers insert into the under surface of the tongue

• Contraction elevates the hyoid bone and draws it forward

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• Infrahyoid Muscles:

1) Sternohyoid

2) Omohyoid

3) Sternothyroid

*All are considered laryngeal depressors

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Sternohyoid

• Flat muscle lying on the anterior surface of the neck

• Originates from the posterior surface of the manubrium of the sternum from the medial end of the clavicle and from the ligamentus tissue

• Fibers coarse vertically and insert on the lower border of the body of the hyoid

• Acts to draw the hyoid bone downward and fixes the hyoid when the lower jaw is open against resistance

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Omohyoid

• Long, narrow 2 bellied muscle

• Located on the anterolateral surface of the neck

• Inferior belly originates from the upper horn of the hyoid

• Prevents the neck region from collapsing during deep inspiration

• Prevents blood vessels of the neck from being compressed

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Extrinsic laryngeal Muscles

Mastoid Tip

Mylohyoid

Hyoid Bone

Sternohyoid

Omohyoid

Sternum

Mandible

Ant.Digastric

Post.Digastric

Stylohyoid

Thyrohyoid

Sternothyroid

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Intrinsic Laryngeal Muscles• Functions:

1) Abduction of the vocal folds for respiration,

2) Fine discrete movements during voice production & closure of the vocal folds and,

3) Protection of the trachea.

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More Specifically...

• change the degree of abduction/ adduction

• change the mass characteristics of the folds

• change the tension of the folds• change the length characteristics of the

folds• react during swallowing- closure of folds• assist in muscular mechanical advantage

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Intrinsic Muscles:

• Cricothyroid: fan-shaped, 2 divisions, Lengthens & tenses the vocal folds.

Action of Cricothyroid

Pars obliquePars recta

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Intrinsic Muscles

• Thyroarytenoid: muscle making up the true vocal folds, 2 parts: thyrovocalis (bound to the vocal ligament) & thyromuscularis (lateral to arytenoids).

ThyroarytenoidVocal ligament

Thyrovocalis

Thyromuscularis

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Thyroarytenoid Functions• decreases the distance between the

thyroid & arytenoid cartilage's,

• shortens the folds,

• decreases tension

• decreases pitch of the voice,

• active contraction lowers pitch of the voice.

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Intrinsic Muscles

• Posterior Cricoarytenoid: Abducts the vocal folds, actively contracted at the end of phonation & any speech sound not requiring v.f. vibration.

PosteriorCricoarytenoid

Action of Post.Cricoarytenoid

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Intrinsic Muscles

• Lateral Cricoarytenoid: lies along upper surface of cricoid cartilage, adducts vocal processes of arytenoids closing membranous portion of v.f.’s.

Action of Lat.Cricoarytenoid

LateralCricoarytenoid

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Intrinsic Muscles

• Interarytenoids (transverse & oblique): Unpaired, 2 part muscle, adducts the v.f.’s in the cartilaginous portion by pulling arytenoid tips together.

ObliqueInterarytenoids

TransverseInterarytenoids

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The Glottis

• The glottis is an open space between the vocal folds.• Size is dependent on what position the v.f.’s are in.• Not a muscle or cartilage.• Abduction- open v.f.’s; Adduction- closed v.f.’s

Glottis

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Ventricular Folds

• Otherwise know as the False Folds,

• superior & lateral to the true vocal folds,

• Their role in phonation?

-No role in voicing

• consist of muscle, but doesn’t have innervation for discrete movements,

• Hyperfunctional voice?

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Activity

1) With you mouth open, hold your breath, then abruptly release it with a vocal tone. What physiologic events occur at the glottis?

2) Produce an /h/ sound alone. What is the status of the glottis? How did it get there?

3) Produce an /h/ sound, then slide into phonation. What muscles are contracting to affect what conditions in the glottis?

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More questions...

1) Place your finger on the laryngeal prominence, alternate between high and low pitched tones. Can you identify a change in the position of the larynx and describe the prime movers?

2) Can you phonate while inhaling? What are the physiological differences?

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Reading/Assignments

• Seikel: Pgs. 183-202

• Dickson: Pgs. 160-176