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Laryngeal Anatomy
1
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 muscles
Suprahyoid & Infrahyoid
• Anatomical position:
Suprahyoid- one of the above
attachments lies above the larynx.
Infrahyoid- one of the attachments lies
below the larynx.
2
Extrinsic Laryngeal Muscles
• Suprahyoid Muscles:
1) Digastric
2) Geniohyoid
3) Hyoglossus
4) Mylohyoid
5) Stylohyoid
• Function: Raise the hyoid bone &
indirectly raise the larynx.
3
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
4
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
5
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
6
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
7
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
8
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
9
forward
• Infrahyoid Muscles:
1) Sternohyoid
2) Omohyoid
3) Sternothyroid
*All are considered laryngeal depressors
10
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
11
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
12
Extrinsic laryngeal Muscles
Mandible
Ant.
Digastric
Post.
Digastric
Stylohyoid
Mastoid Tip
Mylohyoid
Hyoid Bone
Thyrohyoid
Sternohyoid
Omohyoid
Sternothyroid
Sternum
13
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.
14
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
15
Intrinsic Muscles:
Action of Cricothyroid
Pars oblique
Pars recta
• Cricothyroid: fan-shaped, 2 divisions,
Lengthens & tenses the vocal folds.
16
Intrinsic Muscles
Thyroarytenoid
Vocal ligament
Thyrovocalis
Thyromuscularis
• Thyroarytenoid: muscle making up the true vocal
folds, 2 parts: thyrovocalis (bound to the vocal
ligament) & thyromuscularis (lateral to arytenoids).
17
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.
18
Intrinsic Muscles
Action of Post.
Cricoarytenoid
Posterior
Cricoarytenoid
• Posterior Cricoarytenoid: Abducts the vocal folds,
actively contracted at the end of phonation & any
speech sound not requiring v.f. vibration.
19
Intrinsic Muscles
Action of Lat.
Cricoarytenoid
Lateral
Cricoarytenoid
• Lateral Cricoarytenoid: lies along upper surface of
cricoid cartilage, adducts vocal processes of
arytenoids closing membranous portion of v.f.’s. 20
Intrinsic Muscles
Transverse
Interarytenoids
Oblique
Interarytenoids
• Interarytenoids (transverse & oblique):
Unpaired, 2 part muscle, adducts the v.f.’s
in the cartilaginous portion by pulling
arytenoid tips together.
21
The Glottis
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
22
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?
23
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?
24
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?
25
Reading/Assignments
• Seikel: Pgs. 183-202
• Dickson: Pgs. 160-176
26