Communication
Topic 9: The Human Larynx
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
DOT Point(s)
 outline the structure of the human larynx and the associated
structures that assist the production of sound
The Larynx
The Larynx (voice box) is positioned in the throat where the
pharynx divides into the respiratory tract (trachea) and the digestive
tract (oesophagus).
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The Larynx
The Larynx has two main
functions in communication.
1. To provide an open airway
(when breathing)
2. To provide a mechanism for
sound production (when
speaking)
A third function is to ensure a
closed air channel during
swallowing, preventing food or
drink from entering the trachea.
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The Larynx
 The Larynx is a hollow box
which houses the vocal
folds/vocal cords. In humans,
its structure basically consists
of a framework of nine
cartilages (gristle), joined by
membranes and ligaments.
These form a box in which
sound can be produced and
resonate.
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The Larynx
 The upper opening of this ‘box’ is called the glottis, and is often
covered by the epiglottis, the uppermost cartilage of the larynx.
The epiglottis extends from the posterior of the tongue to its
anchor point on the anterior rim of the thyroid cartilage.
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The Larynx
 Being flexible and spoon shaped, the epiglottis tips forward over
the rising larynx during swallowing and prevents food from
entering the larynx and trachea.
 When air is flowing into the larynx, the passage is wide open and
the epiglottis is held away from the larynx.
The Larynx
The large cartilage ring, the
thyroid cartilage, at the top
of the larynx is composed of two
bands which at the join, often
develop a prominence
commonly known as the ‘Adams
Apple’.
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The Larynx
Below this is the cricoid cartilage,
which is attached to the trachea at
the lower edge. Three pairs of
smaller cartilages from part of the
lateral and posterior walls of the
larynx. The most important of these
are the laterally placed arytenoid
cartilages because these anchor the
vocal cords. Muscles connect the
cartilages to the head or neck while
others alter the position, shape and
tension of the vocal folds/vocal
cords.
The Larynx
The interior of the larynx has a mucus-coated lining. Cillia, or hairs,
on the mucous lining below the vocal cords push substances towards
the pharynx. The action of ‘clearing out throat’ helps to move
mucus up and out of the larynx.
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The Larynx
Lying under the mucous lining,
on each side, are the vocal
ligaments. These join some of the
cartilages to each other and in so
doing draw the mucous lining up
to form the vocal folds or true
vocal cords. When viewed from
above the right and left folds
form a ‘V’ shape.
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The Larynx
 The true vocal cords vibrate and may produce sound as air
rushes between them from the lungs through the opening called
the glottis. Above the true vocal cords there is another set of
mucosal folds called the vestibular or the false vocal cords.
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The Larynx
The false vocal cords play no part in sound production but the
mucus produced assists in lubricating the true vocal cords. These
false vocal cords also snap shut if they come into contact with
liquids, preventing them from entering the breathing passages
during drinking.
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Phonation
 Phonation is the name given to the complicated process of
producing intelligible sounds or speech. This process can be
divided roughly into three stages.
1. Production of airflow
2. Production of sound
3. Articulation of the voice
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Phonation
1. Production of airflow
 Air is expelled from the lungs
automatically as we breathe
and as we speak. The force of
air must be great enough to
push open the vocal cords. This
is achieved by the relaxing of
the diaphragm muscle so that
the pressure inside the chest
cavity is higher than that
outside the body.
Phonation
Air is thus forced out in an attempt to equalise the pressure inside
and outside the body. The airflow can be altered in various ways,
such as by exercising, holding your breath, talking and shouting. A
cough can expel a hurricane-force airflow.
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Phonation
2. Production of Sound
The rapid opening and closing of the glottis set up the vibration
pattern, which produces sound. The results from the release of air
from the lungs and the vibration of the vocal cords.
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Phonation
The length of the vocal
folds/cords, and therefore the
size of the glottis, is controlled
by the vagus nerve (the tenth
cranial nerve). One of this
nerve’s functions is the
contraction and relaxation of the
muscles and consequently the
movement of the attached
ligaments and cartilage.
12cranialnerves.wordpress.com
Phonation
The shorter the tenser the
vocal folds, the faster they
vibrate and the higher the
pitch. The glottis is wide open
when we produce deep notes
and just a narrow slit for high
pitched sounds.
en.wikipedia.org
Phonation
A teenage boy’s larynx enlarges comparably more during puberty,
than does a girls. Thus, his vocal folds/cords become longer and
thicker. They vibrate more slowly, resulting in a lower pitch (deeper
voice).
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Phonation
The volume or loudness of the voice is controlled by the strength of
the airflow. The greater the airflow, the stronger the vibration, the
louder the sound.
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Phonation
3. Articulation of the voice
This is the modification of sound we call speech. Sound is an
important medium of communication for humans, particularly if it
is intelligible. The vibration of the vocal folds/cords only produces a
buzzing sound.
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Phonation
The resonance (quality) of a
voice is determined by other
structures situated above the
larynx, such as the pharynx and
the various sinuses of the
cranium. Sinuses are air-filled
cavities which are lined with a
mucous membrane. There is a
significant change in the voice
when a person is blocked up or
has a sore throat.
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Phonation
Finally, in speech, the sounds must be shaped into vowels (a, e, I, o,
u) and consonants (other letters of the alphabet) by the muscles of
the tongue, soft palate, cheeks and lips. These are the associated
structures that assist in the production of sound.
www.whattoexpect.com
Activity
-Handout Anatomy of the Larynx Diagram
-Students to watch video Speech-Language Pathology_ The Vocal
Cords in Action
If time watch:
Larynx - Cartilages - 3D Anatomy Tutorial
www.whattoexpect.com
Homework
-Students to demonstrate how the associated structures (larynx,
lungs, tongue and lips) assist in producing intelligible sounds.
-See First hand invesitgation (Pg 60-61 HSC Biology Options
Communication Text)