Review of Laryngeal Anatomy
As we learned in Module 1, the lungs provide the air source for phonation. The air from the lungs drives the vocal folds, and the upper airway shapes the air source into speech.
The air pressure on the vocal folds produces a periodic sound wave.
This periodic sound wave is phonation. Vowels are one class of sounds that will produce a periodic sound wave. Of course, we can produce aperiodic sounds, such as noises and sounds like "shhh." Most sounds produced in beatboxing would qualify as aperiodic. We can also produce a combination of periodic and aperiodic noises, such as a voiced "hiss."
Let's go over some anatomy. The larynx is located on top of the trachea, below the hyoid bone. You can see a picture of this in your textbook, figure 4.2 on page 72, and in these pictures from Netter. Note the hourglass shape of the view of the larynx in your textbook.
Source: McFarland, D. H. (2008). Netter's Atlas of Anatomy for Speech, Hearing, and Swallowing, Mosby
There are several functions of the larynx, which:
- helps control the flow of air into and out of the lungs
- provides a pathway for oxygen to enter the body and carbon dioxide to exit
- prevents food, water and other substances from entering the lungs
- aids in swallowing
- helps build subglottal pressure for coughing, lifting, vomiting, and defecating
- acts as a sound source for speech
The cartilages of the larynx
The larynx has three cartilages: the thyroid, the cricoid, and the paired arytenoid cartilages. The laryngeal cartilages support the muscles that shape the vocal tract. You can see from the Netter illustration on the left that the cricoid cartilage looks like a signet ring; the front and sides are narrow, and the back is the signet. The arytenoids are pyramidal shaped, and are perched on the top of the cricoid in the back. The thyroid cartilage lies anterior to the arytenoids, and the sides of this cartilage encloses the arytenoids. You can see the angle in the Netter picture in the top left illustration. The size of the angle differs for men and women.