Definition of the Larynx
Also known as the "voice box," the larynx is important for breathing, speaking, and swallowing.
The larynx is an organ made of bone and cartilage located in the center of the throat and contains the glottis.
The glottis is the part of the larynx that's most relevant for speech production. More on that later.
The larynx is partially visible from the outside of your body. If you have a prominent "Adam's apple," you can see it pretty easily. This is the part of the larynx that you felt during the experiment.
Fig. 1 - Part of the larynx is visible outside the body as the "Adam's apple."
Diagram of the Larynx
As fascinating as it is, examining your Adam's apple in the mirror doesn't tell you much about the anatomy of the larynx. If you want to examine the larynx in greater detail without putting a camera in your throat, you can refer to a handy, labeled diagram. This diagram shows a cross-section of the larynx. The next section details each part of the larynx's anatomy.
Fig. 1 - The larynx is the entire "voice box" and includes the vocal folds.
This diagram labels the parts of the glottis as the "vocal cords." The current term used to describe this membrane is "vocal folds." This article uses the term "vocal folds."
Structure of the Larynx
As you can see, the larynx is a delicate organ with many small parts. Each part serves a particular purpose.
Epiglottis
The topmost part of the larynx is the epiglottis.
The epiglottis is a piece of cartilage attached to the base of the tongue that protects the windpipe when swallowing.
Think of the epiglottis as the "lid" of your larynx. When you swallow, it flaps over the top of your larynx to keep food and drink from entering your windpipe. If you've ever laughed while eating or drinking and been sent into a coughing fit, it's because the epiglottis didn't have time to close off the larynx before anything entered it. This allowed the food or drink to "go down the wrong pipe."
Hyoid Bone
Below the epiglottis is the hyoid bone.
The hyoid bone is a horseshoe-shaped bone that sits below your jawbone to support your tongue.
The hyoid bone allows you to change the pitch of your voice. This is explained in the next section.
Thyroid Cartilage
When you look at your Adam's apple, you see your thyroid cartilage.
The thyroid cartilage is a cartilage structure that surrounds the front of the larynx.
Think of the thyroid cartilage as a shield. The vocal folds at the center of your larynx are very delicate; the thyroid cartilage shields them from any outside force.
Cricoid Cartilage
Right underneath the thyroid cartilage, you'll find the cricoid cartilage.
The cricoid cartilage is a circular ring of cartilage that connects the larynx to surrounding muscles.
Trachea
The trachea is the lowest part of the larynx.
The trachea is a tube of membrane tissue and cartilage that connects the larynx to the lungs.
In other words, the trachea is the windpipe. This tube allows you to breathe through your nose and mouth.
Glottis (Vocal Folds)
Finally, the glottis is the part of the larynx with the most significant role in speech production.
The glottis is the part of the larynx that contains the vocal folds, a tissue membrane that allows for voicing in speech.
The glottis looks like a "V" of very thin tissue. Forcing air through the larynx at a high velocity causes this "V" to vibrate, producing a "voiced" sound.
Fig. 3 - This drawing illustrates the glottis in the open position.
The Function of the Larynx in Sound Production
Two structures in the larynx play a major role in speech production: the vocal folds and the hyoid bone. The vibration of the vocal folds provides the sound source for the voice, and the movement of the hyoid bone helps to change the pitch of the voice.
The Role of the Glottis in Sound Production
As was mentioned earlier, forcing air through the larynx causes the vocal folds to vibrate. When you build up enough air pressure under the vocal folds in the closed position, they briefly flap open, letting out a short burst of air, then snap shut again. Once the vocal folds are closed, air builds up under them again, and the process repeats.
This action is repeated hundreds of times per second. The rapid movement of the vocal folds creates a buzzing sound, which is amplified by the rest of your vocal tract. The resulting sound is the sound of your voice.
The Role of the Hyoid Bone in Sound Production
The hyoid bone plays a less important, but still significant, role in sound production. The hyoid bone can raise and lower itself to change your voice's fundamental frequency, or pitch. How does it do that? Well, when the hyoid bone raises itself, it makes the tube of the vocal tract a bit shorter. When air passes through a shorter tube, it produces a higher pitch (think about the length of a bassoon compared to a piccolo). Conversely, when the hyoid bone lowers itself, it slightly lengthens the rest of the vocal tract, lowering the pitch of your voice. This is one of the functions that allow you to speak at different levels or sing different notes.
The Importance of the Larynx in Sound Production
You know now how the parts of the larynx contribute to sound production. But how does that help people communicate?
To start, voicing is the primary sound source for vowels. You can produce vowel sounds without using your vocal folds (by speaking in a whisper), but that will only get you so far. Producing your vowels using vocal fold vibration allows you to speak loudly and intelligibly.
In addition, voicing potentially doubles the number of consonants available in a language. The sounds [p] and [b] differ only in their voicing: [p] is a voiceless bilabial stop, and [b] is a voiced bilabial stop. This small difference allows words like pat and bat to be recognizable as two different words in English.
Finally, changing the pitch of your voice allows for greater potential communication through intonation. Take these two sentences:
Wow, you're a superhero.
Wow, you're a superhero?
These sentences carry different meanings, but the only difference in how they're produced is the audible pitch contour. In languages that utilize intonation in this way, the pitch contour can distinguish a question from a statement, convey differences in emotion, and produce clearer utterances.
Some languages also utilize pitch contours as phonemes. In these languages, low, mid, and high tone movements can distinguish individual words. Chinese, Thai, and Igbo are some examples of tonal languages.
This discussion of the larynx may leave you wondering: is it possible to speak without a larynx? People with laryngeal cancer or other disorders sometimes have to undergo a laryngectomy, or removal of the larynx. Once the larynx has been removed, speaking without assistance from some sort of device is impossible. Some people learn to speak with the help of a plastic, prosthetic larynx inserted during the laryngectomy. Others learn to speak with an electrolarynx: this device produces an artificial buzzing sound similar to vocal fold vibration. The person presses the electrolarynx onto their neck and articulates as normal. The vocal tract amplifies the electric buzzing like it would amplify vocal tract vibration, and the result is robotic-sounding yet intelligible speech.
Larynx - Key takeaways
- The larynx is an organ made of bone and cartilage located in the center of the throat and contains the glottis.
- The larynx consists of the epiglottis, hyoid bone, thyroid cartilage, cricoid cartilage, trachea, and glottis.
- The vibration of the vocal folds provides the sound source for the voice.
- The hyoid bone raises and lowers itself to change the pitch of your voice.
- The larynx provides the sound source for vowel production, distinguishes voiceless and voiced consonants, and allows for greater potential communication through intonation.
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