The Anatomy of the Larynx (2024)

Commonly called the voice box, the larynx is located on top of the neck and is essential for breathing, vocalizing, as well as ensuring food doesn’t get stuck in the trachea and cause choking. Sitting just in front of the esophagus, the vocal folds are located here, making this organ absolutely vital for phonation (making speech sounds). It visibly moves up and down when people swallow. This part of the body can be subject to a number of significant medical conditions, including bacterial infection (laryngitis), laryngeal cancer, and vocal fold paralysis (VFP), which can seriously compromise function.

Anatomy

Structure

The larynx is a complex band of cartilage, ligament, and muscle as well as a mucous membrane. A hollow structure, it’s formed of three large sections of cartilage that are unpaired—the thyroid, cricoid, and epiglottis—as well as six smaller cartilages. Here’s a quick breakdown of the large cartilages:

• Thyroid cartilage: This largest cartilage in the larynx composes the front and side portions of its structure. The right and left halves (laminae) fuse in the midline to create a projection forward—the laryngeal prominence, which is commonly known as the Adam’s apple. This structure is most prominent in post-pubescent males, and it sits just below the superior thyroid notch and just above the inferior thyroid notch, which is at the base of this cartilage. The rear sides of each of the lamina curl upwards into a superior horn, and downwards into a smaller, inferior horn. The former of these, as well as the upper margin of the larynx, attach to the hyoid bone via the thyrohyoid membrane. The inferior horn attaches to the rear, side border of the cricoid cartilage.
• Cricoid cartilage: Sitting just below the thyroid cartilage, the cricoid cartilage is ring-shaped and encircles the airway; it represents the lower portion of the larynx. It is narrower towards the front and wider in the back with a midline ridge that serves as a point of attachment for the esophagus. This cartilage attaches to the thyroid cartilage via the cricothyroid ligament, and to the trachea (also known as the windpipe) via the cricotracheal ligament. Significantly, two paired, pyramidal arytenoid cartilages are along the upper, side portions of the wider part of the cricoid. Each of these has an upper apex, a forward-facing vocal process, as well as muscular portions of the sides.
• Epiglottis: Shaped like a leaf, this cartilage is covered in mucus membrane and is attached to the angle formed by the sides of the thyroid cartilage by a thyroepiglottic ligament. It’s also connected to the hyoid bone along the hyoepiglottic ligament, which runs from the upper, front surface of the epiglottis. The upper margin of this structure is in the pharynx and originates just beneath the root of tongue. As such, it’s just above the opening of the larynx, which contributes to its essential function during swallowing (see below). There is a layer of connective tissue, the quadrangular membrane, that runs between the upper, side borders of the epiglottis and the sides of the arytenoid cartilages. The free-hanging lower edge is thicker and forms the vestibular ligament, which is surrounded by a mucous membrane, thereby forming the vestibular folds. This fold, in turn, connects to the thyroid and arytenoid cartilages.

Finally, there are a couple free-hanging cartilages, the cuneiform cartilages, located in a membrane called the aryepiglottic membrane, which represents the upper margin of the membrane that connects the arytenoid cartilages to the epiglottic cartilage. This is covered in mucus and forms a structure called the aryepiglottic fold.

It’s also important to look at the interior of the larynx, or laryngeal cavity, which houses important structures, including the vocal cords. This space extends along the opening to the lower portion of the cricoid cartilage; it’s thinner in the middle, and wider in the upper and lower portions. Anatomically speaking, it’s divided into three sections:

• Supraglottic section: Between the laryngeal opening and the vestibular folds is the vestibule of the laryngeal cavity. This portion, the walls of which are lined with mucus, is just above the vocal folds, formed by the vestibular ligament as it extends from the epiglottis.
• Glottis: This portion of the larynx, also known as the glottic space, is bounded by the vestibular folds from above, and the vocal cords from below. The walls of this portion bulge out to form recessed areas on the sides known as laryngeal ventricles, which have extensions called laryngeal saccules that extend forward and upwards. These are lined with mucus necessary for vocalization. The vocal cords are four bands of elastic, fibrous tissue, with two upper (superior) and two lower (inferior) ones. The former of these, also known as false vocal cords, are thin and ribbon-shaped with no muscle elements, while the latter are wider and do have musculature covering them. It’s the inferior vocal cords that are able to draw closer together, which is essential for making sound. The opening between these structures is called the rima glottidis.
• Infraglottic cavity: Defined as the space below the glottis and above the trachea, this portion of the larynx starts to widen as it runs downward.

Notably, the larynx is associated with two groups of muscles—extrinsic and intrinsic. The former of these move the structure as a whole and move the hyoid, flexing during swallowing and vocalization. In turn, intrinsic muscles are much smaller, and are involved in moving the actual vocal cords during breathing, vocalizing, and swallowing.

Location

The larynx sits at the front of the neck between the third and seventh neck vertebrae (C3 to C7), where it’s suspended in position. The upper portion of this organ is attached to the lower portion of the pharynx, or throat, via the hyoid bone. Its lower border connects to the upper portion of the trachea (also known as the windpipe), which is an important part of the upper respiratory system.

Anatomical Variations

Primarily, differences are seen between male and female larynxes. In men, this feature is more prominent, largely because of a thicker thyroid, and it is angled at 95 degrees, versus 115 degrees in women. As with many parts of the body, there are also a number of other anatomical variations:

• Triticeal cartilage: The most common variation of this part of the body involves the presence of an additional structure called the triticeal cartilage. Seen in anywhere from 5% to 29% of people, this small, oval-shaped cartilage is found within the side border of the thyrohyoid membrane (which connects the hyoid bone to the thyroid cartilage). Largely, the function of this variant is unknown.
• Variant laryngeal enervation: Differences in the nerve structure of the larynx are quite common and may vary from person to person. The primary laryngeal nerve has been observed to split into two or three branches, which affects where it accesses different structures, such as the cricothyroid joint. These differences can have serious implications in surgery.
• Agenesis of thyroid horns: Anatomists have also observed a lack of development of the upper horns of the thyroid cartilage. This is seen in anywhere from 0.8% to 9.4% of people, and it can cause the larynx to be asymmetrical. This, too, can impact the surgical treatment of this region.

Function

As noted above, the larynx primarily is an organ associated with vocalization and making sound. Basically, when you exhale, air is pushed through the glottis, and, it’s the vibrations of the vocal cords that produce noise and sound. During speech or vocalization, the positioning of these vocal cords changes to affect pitch and volume, which can be further modulated by the tongue and relative position of the mouth as necessary for speech.

Additionally, the larynx plays an important role in preventing food from becoming stuck in the airway. When people swallow, the epiglottis shifts downward, blocking off the trachea. The food or liquid then moves to the esophagus, which runs alongside the trachea, and delivers material to the stomach.

Associated Conditions

A number of conditions can affect this part of the body. These vary from inflammations due to illnesses to cancer. Primarily, these include:

Laryngitis

This inflammation of the larynx can be chronic—that is, lasting over three weeks—or acute, with the former being more common. Symptoms of this condition include hoarse voice, pain, couching, and, in some cases, fever. Acute laryngitis is often the result of either viral or bacterial upper respiratory tract infection, with a significant number of cases resulting from fungal growth. Chronic cases tend to be the result of smoking, allergies, or stomach acid reflux. Those who use their voices often, such as singers, teachers, and those in other professions, may experience inflammation of the larynx due to overuse.

Vocal Fold Paralysis

Resulting from paralysis of the laryngeal nerve, which innervates the intrinsic laryngeal muscles, vocal fold paralysis (VFP) is the result of a number of conditions, including head or neck injury, stroke, tumors, infections, or other neurological issues. As a result, speech and vocalization function can be severely impacted. This condition sometimes resolves on its own, though speech-language therapy or treatment of underlying causes may be needed to take on this issue.

Laryngeal Cancer

This form of cancer arises in the glottis, and, like others, can spread aggressively. This leads to hoarseness, changes in voice, the development of lumps in the neck, cough, as well as challenges swallowing. As with other cancers, patients undergo either surgery, chemotherapy, or radiation therapy.

Tests

Careful assessment of the larynx is necessary to ensure proper diagnosis of any condition as well as overall function. Here’s a quick breakdown:

• Mirror laryngoscopy: A test that’s been employed for over a century, this approach involves inserting a special mirror into the back of the mouth to allow the specialist to visually assess the larynx.
• Flexible fiberoptic laryngoscopy: The most widely used examination, flexible fiberoptic laryngoscopy entails the use of a tool called an endoscope (basically a specialized tube with a camera at the end) that is inserted through the nostril to capture images of the interior of the larynx. Testing is done as the patient swallows, talks, or sings to assess issues such as vocal fold paralysis or functional problems due to neurological conditions, among others.
• Rigid transoral laryngoscopy: This type of laryngoscopy employs a rigid endoscope that has a light attached to it. This tool’s camera can deliver high-quality images to the doctor and allows for more careful analysis. It’s used to identify subtler or less easily discerned issues in the larynx.
• Stroboscopy: This technique involves the use of a specialized microphone that’s placed on the skin just above the larynx. This device registers the frequency of the voice and translates it to a strobe light that flashes just out of sync with this frequency, producing a video image of the motion of the vocal folds. This method is ideal for analyzing problems with the health of the surface of the vocal cords, such as lesions.