Talk May Be Cheap, but the Larynx Makes It Possible

Part of the larynx structure includes the voice box, also sometimes referred to as the vocal cords. Although these names suggest boxes and cords, neither moniker is really accurate. The vocal cords are actually two bands of smooth muscle tissue that are located in the larynx, and these muscles vibrate as air moves through them on its way to or from the lungs.

"During sound production, the vocal folds close together and start vibrating as air is expelled from the lungs and passes between them and into your mouth, which helps to make the sounds we hear when we are listening to people talk," says Giuseppe Aragona, M.D., in an email interview.

The larynx comprises a cartilage skeleton that contains the vocal cords covered by a mucus lining. These "cords" are flexible muscles that are extremely adept at changing shape, position and tension so the voice can make a range of sounds at a variety of levels. If the larynx becomes inflamed because of illness or injury, the vocal cords can swell and cause laryngitis, which is characterized by a hoarse, gravelly-sounding voice — or the loss of one's voice altogether.

"If there is swelling to a vocal cord (from over-use, cancers, trauma) the tone and function produced by the vocal cord becomes altered. The sounds can also change by injury to the muscles, or to nerves that innervate [give sensation to] the vocal cords," says Taylor Graber, M.D., in an email interview.

You need vocal cords in good working order to whisper, right? Actually, it's possible to whisper without using the ol' voice box. When you whisper, the vocal cords stay slack and do not vibrate. This is known as an "open throat" whisper, and it allows people who are mute to make sound. It's also a helpful technique for people who are resting their voices, such as singers or those with a sore throat. However, most people don't use this passive technique when they whisper. Instead, they strain to produce sound and this can be just as harmful to the vocal cords as shouting.

If animals and humans both have larynx (plural), then why is speaking a uniquely human ability? Our brain formation has something to do with it, but people have an especially complex system comprising the larynx, which produces sound, and a flexible mouth, tongue and lips that allows us to generate the precise sounds language requires. When we talk, air moves from the lungs through the larynx and that sound is shaped by the extreme fine motor control found in the throat, mouth, tongue and lips.

"The larynx has an essential role to play when it comes to every human's speech and is essential to helping create the way words sound when they leave the mouth, forming what we have come to understand as language," Aragona says.

There are about 60,000 people in the United States who have had their larynx removed, but only a few who have had a larynx transplant. Few people qualify, and if they do, the surgery is complex, takes about 18 hours and is hampered by a shortage of larynx available to transplant. However, new initiatives — including lab-grown and 3D-printed larynx have the potential to help people recover their own voices again.

The hyoid is a u-shaped bone situated at the front of the throat above the larynx, according to Graber. "It forms the attachment for multiple muscles in the neck, which aid in tongue movement and swallowing," he says.

What's really unusual about this larynx-related bone is that it has the distinction of being the only bone in the human body that is "free-floating," which means it isn't connected to any other bone. Instead, it is supported by connective tissue. The hyoid is only found in humans and Neanderthals, and is believed to be the foundation of our ability to speak.

The biology of puberty brings on changes, but for boys, this growth involves a unique transformation in the larynx, too. During childhood, the voice boxes of boys and girls are the same size, but when boys hit their tween and teen years, their vocal cords hit a growth spurt. This growth causes their voices to "crack" and eventually results in a deeper, more resonate, tone.