Designed for Communication
Your larynx is a very specialized and complex organ that lies at the base of your throat. It is an essential part of your air passages, as it connects your pharynx, or throat, with your trachea, or windpipe. The larynx also serves as a valve that prevents swallowed food, liquids, and other foreign items from entering your airways.
While these are important functions, your larynx is specifically designed to be a phonating mechanism. Phonation, or vocalization, occurs when you push air from your lungs across your vibrating vocal cords to produce sounds. (Your vocal cords, which are stretched like violin strings across your inner larynx, are also known as vocal folds.) Through movements of its cartilages, your larynx changes the tension of your vocal cords and the width of the opening between them, thereby varying the pitch of the sounds you produce.
Due to its participation in phonation, your larynx is also called your 'voicebox.'
The skeleton of your larynx is composed of nine cartilages that are joined together and supported by a series of ligaments, muscles and membranes. Three of these cartilages (the cricoid cartilage, the thyroid cartilage, and the epiglottis) are single, and three (the cuneiforms, corniculates, and arytenoids) are paired.
The largest cartilage in your larynx is the thyroid cartilage. It is roughly cone-shaped, being slightly narrower at the bottom, with a number of notches and horn-like projections. When viewed from above, the thyroid cartilage is C-shaped, with the open part of the 'C' pointing toward the back of your neck. When viewed from the back, it looks like the wings of a bat reaching out to enfold the other structures of the larynx. The front of the thyroid cartilage is somewhat pointed and can be easily felt (and seen, if you're a mature male) as your 'Adam's apple.'
The cricoid cartilage is smaller than the thyroid cartilage, but it is thicker and stronger. Unlike the thyroid cartilage, which is open at the back, the cricoid forms a complete ring. ('Cricoid' is a Greek word for ring.) On its lower edge, the cricoid cartilage is attached to your trachea by a tough membrane. The slightly wider thyroid cartilage rests atop the cricoid, much like two glasses stacked in your kitchen cupboard.
The other single cartilage in your larynx, the epiglottis, serves as a protective cover for the entire larynx. The leaf-shaped epiglottis is attached by a slim band to the top front rim of your thyroid cartilage. Whenever you swallow, the epiglottis flops down over the top of your larynx, like the lid of a garbage can, and diverts food or fluids into your esophagus, which lies directly behind your larynx. Your esophagus then directs the swallowed material into your stomach.
The other six cartilages of your larynx - two arytenoids, two cuneiforms, and two corniculates - are involved in suspending, moving, and protecting your vocal cords. The largest and most important of the paired cartilages are the arytenoids, which are shaped like two three-sided pyramids.
The bases of the arytenoids rest upon the top rim of the cricoid at the back of your larynx. One end of a vocal cord is attached to the front side of each arytenoid cartilage. The other ends of the vocal cords are firmly attached to the inner surface of the thyroid cartilage, whose arms form the front wall of your larynx and encircle the top portion of the cricoid cartilage, your vocal cords, and the arytenoids.
Perched atop the arytenoids, like two horns on a bull's head, are the corniculate ('horn-like') cartilages. They help make the arytenoids taller. The cuneiform ('wedge-like') cartilages are buried in a tough, elastic sheath that stretches from the arytenoids to the epiglottis. When you swallow and the epiglottis folds downward, the cuneiforms wedge against the epiglottis to help stabilize the 'lid' over your larynx and form a tighter seal.
The Vocal Cords
Your vocal cords are the source of the sounds that emanate from your larynx. Each of your two vocal cords is constructed of a tough, fibrous strand - the vocal ligament - which forms the free upper and inner edge of the vocal cord.
Extending downward and outward from the vocal ligament and attaching to the cricoid cartilage is an elastic membrane called the conus elasticus. Together, the conus elasticus and vocal ligament form one vocal cord. The two vocal cords look like the roof of a peaked tent whose top can be opened and closed to permit the passage of air. The opening between the vocal cords is called the rima glottidis, or simply the glottis.
The arytenoid cartilages, which anchor the vocal cords at the rear of your larynx, play a major role in tightening and moving your vocal cords in and out to vary the pitch of the sounds you make.
A fold of tissue, called the ventricular fold, lies directly above your vocal cords. The ventricular fold is sometimes called a 'false vocal cord,' but it does not participate in phonation. It probably helps close the upper part of your larynx during swallowing. Between the vocal cord and the ventricular fold is a small recess called the ventricle.
Muscles of the Larynx
The muscles of your larynx are divided into two main groups. The extrinsic muscles (extrinsic means 'outside') move your larynx as a whole unit. There are nine pairs of extrinsic laryngeal muscles that elevate (lift) or depress (lower) your larynx.
The intrinsic muscles (intrinsic means 'inside' or 'within') are involved in movements of individual laryngeal parts, altering the length and tension of your vocal cords, and adjusting the size of the opening between your vocal cords. Some anatomists count nine intrinsic muscles in the human larynx, while others combine some muscle groups to get six or seven. All but one of the laryngeal muscles - the transverse arytenoid muscle - are paired.
The intrinsic muscles perform two principal functions. By tightening the upper opening of your larynx during swallowing, they help prevent foreign material from entering your airway. By moving the arytenoid cartilages or tilting the thyroid cartilage on the cricoid cartilage, they alter the conformation of your vocal cords to allow changes in phonation.
Your larynx, or 'voicebox,' is an extremely complex structure whose primary function is phonation, or vocalization. It also serves as a conduit between your upper and lower respiratory tracts.
Your larynx is composed of a cartilage skeleton consisting of three single and three paired cartilages. From top to bottom, the three single cartilages are the epiglottis, the thyroid, and the cricoid. The epiglottis forms a protective lid for the larynx, while the thyroid and cricoid cartilages provide structural strength and participate in phonation. The cricoid cartilage is directly attached to the upper end of the trachea.
Of the three paired cartilages - arytenoid, cuneiform, and corniculate - the arytenoids play the largest role in phonation. Your vocal cords, which produce sounds when pressurized air moves over them, are suspended between the arytenoid cartilages and the thyroid cartilage.
Rotational and tilting movements of the arytenoids, in conjunction with tilting of the thyroid cartilage on the cricoid cartilage, produce conformational changes in the vocal cords and alter the size of the rima glottidis, which is the opening between the vocal cords. These actions allow you to vary the pitch of sounds emanating from your larynx.
The larynx is moved up and down as a unit by nine pairs of extrinsic muscles. Of the intrinsic laryngeal muscles, only one - the transverse arytenoid muscle - is unpaired.
After you have finished, you should be able to:
- State the purpose and function of the larynx
- Name the single and paired cartilages in the larynx
- Describe the structure of the vocal chords
- Identify the muscles of the larynx and their purposes
To unlock this lesson you must be a Study.com Member.
Create your account
Register to view this lesson
Unlock Your Education
See for yourself why 30 million people use Study.com
Become a Study.com member and start learning now.Become a Member
Already a member? Log InBack