Anatomy

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The larynx is designed to control the flow of food, air and sound. For example, when a person takes a sip of coffee, swallows, breathes in and then engages in conversation, liquids and solids are separated from the inhaled breath (air) and then directed down the esophagus. Air is directed between the vocal cords into his and her lungs. The air is put to use again to make sound on its way back out. The larynx does all of this work, all very rapidly.

Thus, the larynx is basically a valve, a talented valve, with three functions:

  1. regulate breathing,
  2. create sound, and
  3. keep food and liquids out of the lungs. 

During a swallow, we see a bulge moving up and down on the front of the neck. We call this protuberance in a man’s neck, the “Adam’s apple” or medically speaking in all necks, the thyroid cartilage. The thyroid cartilage starts out soft and enlarges when exposed to testosterone, perhaps partly for evolutionary mating reasons. The net external effect is that it protrudes visibly. On the inside testosterone thickens and elongates the vocal cords. The longer and thicker they end up, the lower the notes they are capable of producing. The thyroid cartilage sits on top of the cricoid cartilage. Below the larynx is the windpipe or trachea which you can feel in some people with thin necks. Above the Adam’s Apple is the hyoid bone which helps suspend the larynx in the neck.

The larynx anatomy

The hyoid bone (top yellow) is connected to the tongue and jaw muscles above and the thyroid cartilage below. The thyroid cartilage (central blue) is also known as the Adam's Apple and protects the vocal cords which are attached on the backside in the middle. The cricoid cartilage (lower green) is a complete ring supporting the bottom of the larynx.

Endoscopic views of the larynx will be internal from the point of view of an endoscope, a view from above, which is available for easy access by anyone with an endoscope. A rigid endoscope views the larynx from the back of the mouth. A flexible endoscope views the larynx from the back of the nose. 

Rigid laryngoscope

A rigid endoscope is passed through the mouth to visualize the vocal cords. It is difficult to say much of anything other than “eeeeee” while the examiner holds your tongue, but it does provide a very clear picture of the vocal cords. Most people need some topical anesthesia in order to keep from gagging during this examination.

flexible laryngoscopy

A flexible endoscope is passed through the nose. At the back of the nose, it is angled downward to view the vocal cords.

The space inside the throat above the larynx is the pharynx. It is surrounded by muscles and the hyoid bone. Changing the shape and size of the pharynx alters resonance.

Pharynx

Left: The pharynx is the opening around the larynx and here it is relaxed and open (yellow arrows). Right: The pharynx is being squeezed to amplify or improve the resonance of high pitched sounds.

Technically the larynx has two cartilages that maintain its shape (thyroid and cricoid). A softer cartilage acts as a diverting valve during swallowing (epiglottis). Two smaller cartilages open and close the vocal cords (arytenoids) and some miniscule cartilages sit on the arytenoids seeming to act as a dam to prevent residual liquids in the throat from entering the airway.

Endoscopic laryngeal anatomy

The soft curved cartilage in the middle of the photo is the epiglottis (blue arrow). It’s base is attached to the back of the thyroid cartilage just above the vocal cords (the inverted V in the middle of the picture). The epiglottis comes in many different shapes and it folds over when swallowing to cover the vocal cords. The corniculate cartilages rest on top of the arytenoid cartilage (yellow arrows).

Arytenoids -  arytenoid cartilage

Left: The arytenoids (approximate location colored yellow) open. The round tracheal rings are partially visible beneath the vocal cords. Right: The arytenoids bringing the vocal cords together to make sound. 

 

The front of the thyroid cartilage is triangular or tent-like in shape suspending and protecting the vocal cords, with the Adam’s apple representing the apex. Inside, the airway is essentially a round tube with the vocal cords narrowing the airway, acting as a valve, technically – the glottis. The vocal cords narrow the opening to a triangle. During exhaling (breathing out), the vocal cords narrow the triangle to keep some back pressure in the lungs. During phonation, the vocal cords come almost completely together to form a narrow slit. Air passing between the vocal cords sets them vibrating and generates sound.

Vocal cord positions

Left: The vocal cords form a triangle when breathing in, Middle: narrow the triangle when breathing out and, Right: line up parallel to form a slit during sound production.

There are 10 internal muscles, vocal ligaments and some glands for lubrication. This is all covered with delicate, nearly translucent mucosa, tinted pink when viewed from far away by the blood flowing beneath it. All of this sounds complicated, but the machinery of the voice box is elegantly simple, with each component serving a specific purpose. Let’s take a closer look at the muscles, or if they are deep beneath the surface, we will visualize their action by their effects in the photos.