Pharynx

Definition of the pharynx

The simplest definition of the pharynx is the throat. To be more specific, though:

The pharynx forms the back wall of the nasal cavity and mouth. It connects the nose and mouth to the larynx, which provides passage to the esophagus and the windpipe.

Pharynx: diagram

The pharynx can be difficult to visualize without consulting a diagram. Examine the pharynx from the bottom up by looking at this vocal tract diagram.

Fig. 1 - The pharynx is divided into the nasopharynx, oropharynx, and laryngopharynx.

Pharynx: structure

As you can see from the diagram, the structure of the pharynx is fairly simple. The pharynx structure is divided into three main component parts based on the neighbouring structures: the laryngopharynx, the oropharynx, and the nasopharynx.

Laryngopharynx

If you put your hand on your throat and then swallow, you can feel a hard structure move beneath your hand. This structure goes by a few different names: the adam's apple, the voice box, and—most scientifically—the larynx.

A flap of cartilage called the epiglottis divides the top of the larynx from the bottom of the laryngopharynx.

The laryngopharynx contains the root of the tongue, the tonsils, and the back wall of the throat. Its job is to transport air that comes through the larynx toward the upper levels of the pharynx.

Oropharynx

When you shine a flashlight into your mouth to examine a sore throat, you primarily see the oropharynx.

The oropharynx channels air from the laryngopharynx to the mouth when you breathe and speak.

Nasopharynx

The top part of the pharynx is the nasopharynx.

The nasopharynx channels air from the laryngopharynx to the nasal cavity, allowing you to breathe through your nose. When you produce non-nasal sounds (like [p] or [s]), you block air from flowing through the nasal cavity by pushing your velum against your nasopharynx.

Pressing the velum against the nasopharynx forces air to only flow from your oropharynx to your mouth.

The function of the pharynx: sound production

The pharynx's primary function in sound production is guiding airflow through the nose and mouth. This allows your vocal tract to amplify and filter the pressure wave from your voice into meaningful sounds. But the pharynx can also define the tone of your voice.

If you've ever tried to sound like an old British wizard (who hasn't?), you know what it feels like to control the pharynx while speaking. To speak in a very deep, ancient voice, you have to:

1. tense up the muscles in your pharynx, making your throat stiff, and
2. lower your larynx, thus extending your pharynx and making your throat longer.

You might have to angle your head downward to lengthen your pharynx and produce this wizardly sound. This effect is important! In fact, human language exists because of the specific angle of the skull and its effect on the pharynx.

The importance of the pharynx in sound production

Beyond amplifying the voice and channelling airflow, the pharynx plays a hugely important role in sound production. The pharynx is one of the structures that allowed humans and their ancestors to develop complex communication systems. Spoken language would not be possible without the especially-long human pharynx.

Comparing the anatomy of humans and chimpanzees helps explain this. The human skull is more arched and forward-leaning than the chimpanzee skull. The skull of an ancestor to humans, homo Erectus, is somewhere in the middle: more arched and forward than the chimpanzee, but less so than the human. The skull's greater arch and forward tilt stretches out the pharynx and lowers the larynx. As a result, humans have a much longer pharynx than their ancestors and current relatives.

Fig. 2 - The human pharynx is very long compared to the chimpanzee pharynx, allowing for a wider range of tongue movement.

How does this affect speech? Speaking requires you to move your tongue around in precise ways. You might remember from the diagram that the root of the tongue is in the laryngopharynx, the lowest part of the pharynx. A long pharynx provides the tongue with plenty of room to move around. This allows for the wide range of vowels and consonants necessary for a spoken language.

The pharynx is an integral part of the vocal tract not only because it connects the larynx to the oral and nasal cavities, but also because it makes spoken language possible. It sets the human species apart from its relatives and allows people to communicate, connect, and collaborate.