Download Laryngeal Anatomy and

6/21/2013
Simon Best
June 21, 2013
Laryngeal
a y gea Anatomy
ato y a
and
d
Physiology
Milton J. Dance Center & Johns Hopkins Voice Center
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Outline
•
•
•
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Basic Laryngeal Function
Laryngeal Anatomy
Laryngeal Neurophysiology
Voice Production
– Cover body theory
– Layered Microstructure
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Laryngeal Phylogeny
• Study of the primitive larynx
• What is the basic function of the larynx?
• How has it evolved to suit this function?
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Primitive Larynx
• Primitive larynx = muscular sphincter to
protect the lower airway from intrusion of
foreign matter.
• Secondary development = enhance
ventilatory flow through active dilation of
laryngeal aperture
• Voice = a late, specialized function
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Separation of respiration and
deglutition
• Shield
Shield-like
like shape of epiglottis
epiglottis, height of
aryepiglottic folds
• Lateral diversion of food into piriform
fossae
ossae
• Elevation of larynx during swallowing
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Posterior View
• Preservation of
height of AE fold
during supraglottic
operations
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Vocal Fold Adaptations
• Length of human vocal fold: 11
11- 15 mm
• Ratio of arytenoid length to
membranous vocal fold is 4:10
– Ideal ratio for cross
cross-sectional
sectional area for
respiration is 7:10
• Gazelle, horse
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Outline
•
•
•
•
Basic Laryngeal Function
Laryngeal Anatomy
Laryngeal Neurophysiology
Voice Production
– Cover body theory
– Layered Microstructure
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Thyroid Cartilage
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Cricoid Cartilage
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Cartilaginous Larynx
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Ventricular Folds (False Vocal Folds)
• Superior
S
i and
d llateral
t l tto TVF
TVFs
• Space between the TVFs and
FVFs is called the Ventricle
• Ideally, the FVFs retract as far
away from mid-line as possible
during phonation to allow
maximum vibratory freedom of
the TVFs.
Extrinsic Muscles
• Responsible for
supporting
pp
g and
positioning the larynx for
speech, swallowing, and
airway protection.
• Can move the entire
vocal complex up or
down the distance of one
vertebra.
• Can be divided into two
groups:
1.
2.
Surprahyoid
Infrahyoid
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Outline
•
•
•
•
Basic Laryngeal Function
Laryngeal Anatomy
Laryngeal Neurophysiology
Voice Production
– Cover body theory
– Layered Microstructure
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Neurophysiology of Muscular
Larynx
Nerve
Superior laryngeal
(external division)
Muscle
Action
Cricothyroid muscle
Adductor, isotonic tensor
Thyroarytenoid muscle
Adductor, isometric tensor
Lateral cricoarytenoid muscle Adductor
Interarytenoid muscle
Adductor
Posterior cricoarytenoid
muscle
Abductor
Recurrent laryngeal
Tracheoesophageal mucosa
Tracheal smooth muscle
Nerve of Galen
(communicating
branch)
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Autonomic (secretory)
Autonomic
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Sensation of Larynx
• Superior Laryngeal nerve (internal
branch)
– Superior border of larynx to true vocal folds
• Recurrent Laryngeal
y g
nerve
– Below true vocal folds
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Neurophysiology of
Protective Function
• Glottic closure reflex strongly influenced
by arterial pCO2 levels
– Reflex gets weaker as pCO2 rises
– Laryngospasm during emergence from GA
– Pardoxical VF motion / Laryngospasm
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Neurophysiology of
Respiratory Function
• EMG of PCA muscle
• Intratracheal pressure
– Nasal
– Mouth
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Neurophysiology of
Respiratory Function
• One week s/p tracheotomy
– Open
– Occluded
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Neurophysiology of
Respiratory Function
• Four weeks s/p tracheotomy
• Role for progressive downsizing of trach
and capping trials
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Outline
• Basic Laryngeal Function
• Laryngeal Anatomy
• Laryngeal Neurophysiology
– Board Review: Laryngeal Botox
• Voice Production
– Layered Microstructure
– Cover body theory
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Layered Microstructure
Cover {
} Body
Vocal Ligament
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Layered Microstructure
• Epithelium: Non-keratinizing
Non keratinizing squamous
• SLP: loose fibrous and extracellular
matrix; glycoproteins, elastin
• Vocal Ligament: dense collagen
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Aerodynamic-Myoelastic Theory
• Vertical Phase
Difference:
– Lower lip (elastic in
nature) tends to
spring back into
place as upper
margins are still
moving
i away ffrom
one another.
– Lower lip always
leads
– Essential to normal
voice production
Low to High
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Conclusions
• The functions of the larynx are:
1. Airway protection
2. Respiration
3. Voice
• A very complex neurologic system, and
an exquisitely tuned vibrating sound
source.
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