Speaking and singing involve a voice mechanism that is composed of three subsystems. Each subsystem is composed of different parts of the body and has specific roles in voice production.

Subsystem	Voice Organs	Role in Sound Production
Air pressure system	Diaphragm, chest muscles, ribs, abdominal muscles Lungs	Provides and regulates air pressure to cause vocal folds to vibrate
Vibratory system	Voice box (larynx) Vocal folds	Vocal folds vibrate, changing air pressure to sound waves producing "voiced sound," frequently described as a "buzzy sound" Varies pitch of sound
Resonating system	Vocal tract: throat (pharynx), oral cavity, nasal cavities	Changes the "buzzy sound" into a person's recognizable voice

The ability to produce voice starts with airflow from the lungs, which is coordinated by the action of the diaphragm and abdominal and chest muscles. The voice box (larynx) and vocal folds (sometimes called vocal cords) comprise the vibratory system of the voice mechanism.

The vocal tract is comprised of resonators which give a personal quality to the voice, and the modifiers or articulators which form sound into voiced sounds.

The key function of the voice box is to open and close the glottis (the space between the two vocal folds).

• Role in breathing: open glottis
  • Voice box brings both vocal folds apart during breathing.
• Role in cough reflex: close, then open glottis
  • Voice box closes the glottis to build up pressure, then opens it for the forceful expelling of air during cough.
• Role in swallowing: close glottis
  • Voice box coordinates closing the glottis by bringing both vocal folds to the midline to prevent choking during swallowing.
• Role in voice: close glottis and adjust vocal fold tension
  • Voice box brings both vocal folds to the midline to allow vocal fold vibration during speaking and singing.
  • Voice box adjusts vocal fold tension to vary pitch (how high or low the voice is) and changes in volume (such as loud voice production).

• Cartilages
• Muscles
• Nerves
• Vocal Folds

There are three cartilages within the larynx.

1. Thyroid Cartilage
   • Forms the front portion of the larynx
   • Most forward part comprises the "Adam's apple"
   • Houses the vocal folds
   • Vocal folds attach just below the Adam's apple
2. Cricoid Cartilage
   • Below the thyroid cartilage
   • Ring-like: front to back
   • Becomes taller in the back of the voice box
   • Platform for the arytenoid cartilages
3. Arytenoid Cartilages (left and right)
   • Pair of small pyramid-shaped cartilages
   • Connect with the cricoid cartilage at the back of the vocal folds
   • With the cricoid cartilage, forms the cricoarytenoid joint

Voice box muscles are named according to the cartilages to which they are attached.

Muscles, Cartilage Attachments, and their Main Roles	Nerve Input
Muscles That Position Vocal Folds in the Midline During Sound Production (close glottis)
Thyroarytenoid muscle R & L muscles; attached to thyroid and arytenoid cartilages on each side Action shortens and relaxes vocal ligament Note: deeper inner fibers referred to as "vocalis muscle" (see below) Lateral cricoarytenoid muscle (R & L muscles) Attached to cricoid and arytenoid cartilage on each side Closes or adducts vocal folds Inter-arytenoid muscle (transverse and oblique) Attached between right and left arytenoid cartilages Closes inlet of larynx These muscles work coordinately to position both vocal folds in the midline for vocal fold vibration during sound production. Role in voice production Role in protection of airway during swallowing	Recurrent laryngeal nerve (RLN)
Muscle That Moves Vocal Folds Apart (open glottis)
Posterior cricoarytenoid muscle Attached to cricoid and arytenoid cartilages o Move arytenoid cartilages so as to move both vocal folds apart, "open" of abduct vocal folds Role in breathing	Recurrent laryngeal nerve (RLN)
Muscles That Adjust Length and Tension of Vocal Folds
Vocalis muscle (derived from inner and deeper fibers of thyroarytenoid msucle] Alters vocal fold tension/relaxation during speaking or singing Role in voice production	Recurrent laryngeal nerve (RLN)
Cricothyroid muscle Attached to cricoid and thyroid cartilages Tilts the thyroid cartilage, thus increasing tension of vocal folds Role in high-pitch singing Role in pitch glide in singing	Superior laryngeal nerve (SLN)

• The brain coordinates voice production through specific nerve connections and signals
• Signals to the voice box for moving voice box muscles (motor nerves) come from:
  • Motor branches of recurrent laryngeal nerve (RLN)
  • Superior laryngeal nerve (SLN)
• Signals from the voice box structures for feeling (sensory nerves) travel through sensory branches of the RLN and SLN

The left and right vocal folds are housed within the larynx. The vocal folds include three distinct layers that work together to promote vocal fold vibration.

1. Covering/mucosa: Loose structure that is key to vocal fold vibration during sound production; is composed of:
   • Epithelium
   • Basement membrane
   • Superficial lamina propria (SLP)
2. Vocal ligament: The vocal ligament is composed of:
   • Intermediate lamina propria
   • Deep lamina propria (contains collagen fibers that are stronger and more rigid than the superficial lamina propria)
3. Body: The vocal fold body is composed of the thyroarytenoid muscle. This muscle helps close the glottis and regulate tension of vocal fold during speaking and/or singing. The medial portion of this muscle is also called "vocalis muscle."

The vocal folds move similar to a car's windshield wipers that are attached to the middle of the windshield and open outwards. (See figure below.)

• The front ends of both vocal folds are anchored to the front-middle (anterior commissure).
• The back ends of both vocal folds are anchored to the arytenoid cartilages.
• When arytenoids are moved to the open position by the posterior cricoarytenoid muscle, vocal folds open, resulting in glottal opening.
• When arytenoids are closed by the lateral cricoarytenoid and inter arytenoid muscles, vocal folds are brought to the midline resulting in glottal closure.

Understanding How Voice Is Produced

How Breakdowns Result in Voice Disorders