Voice Production Anatomy: Larynx, Vocal Cords & Respiration

Posted on Apr 4, 2025 in Biology

The Diaphragm

• A large, dome-shaped muscle located below the lungs.
• Essential for the process of breathing.

The Trachea (Windpipe)

A tube providing passage for air between the larynx and the bronchi.

• Provides protection for the respiratory system.
• Composed of C-shaped cartilaginous rings that keep the airway open.

The Larynx

Also known as the voice box, it is composed of several cartilages:

• V-shaped structures composed of muscles and ligament membranes.
• Positioned horizontally within the larynx.
• Joined at the front (anteriorly) to the thyroid cartilage and at the back (posteriorly) to the arytenoid cartilages.
• Appear whitish or beige when healthy.

The Arytenoids

• Located at the back (posterior) ends of the vocal cords.
• Made of cartilage.
• Crucial for opening, closing, and tensing the vocal cords, thus facilitating vibration and pitch changes.

The Glottis and Vocal Cord Positions

The glottis is the space between the vocal cords. Its configuration changes for different activities:

1. Breathing: Vocal cords are wide open (abducted) to allow free airflow.
2. Whispering: Vocal cords are slightly adducted (closed), creating turbulence but no phonation (voicing).
3. Speaking: Vocal cords vibrate (adduct and abduct rapidly) for voiced sounds or remain open for voiceless sounds.
4. Glottal Stop: Vocal cords are tightly closed (adducted) and tense. Air pressure builds up below and bursts out upon release (e.g., coughing, the middle sound in “uh-oh!”).

How Speech is Produced

The larynx (voice box) contains the two vocal cords. When egressive (outgoing) air comes up from the lungs through the trachea, it reaches the larynx. If the vocal cords are appropriately positioned (adducted), they vibrate as the air passes through. This initial sound (phonation) is then amplified and modified in quality by the resonators (pharynx, oral cavity, nasal cavity), and finally, the articulators (tongue, lips, teeth, palate) shape the sound, producing recognizable speech sounds.

Resonators

Resonating cavities amplify sound and modify its volume and quality (timbre). The primary resonators for speech are the pharynx, oral cavity, and nasal cavity.

The Pharynx

The pharynx is a muscular tube connecting the nasal cavity and mouth superiorly to the larynx and esophagus inferiorly. It is divided into three parts:

• Nasopharynx: The part posterior to the nasal cavity.
• Oropharynx: The part posterior to the oral cavity (mouth).
• Laryngopharynx: The part inferior to the oropharynx and opening into the larynx and esophagus.

Articulators

Articulators are the parts of the vocal tract, primarily within the oral cavity, that move to shape the sound produced by the vocal cords and modified by the resonators into specific speech sounds.

The Tongue

A highly mobile and flexible muscular articulator, typically divided into functional areas:

• Tip
• Blade
• Front
• Centre
• Back
• Root

It possesses great mobility, allowing for a wide range of sound formations.

The Soft Palate (Velum)

Characteristics:

• An area of soft tissue located at the back of the roof of the mouth (posterior to the hard palate).
• Ends in the uvula, a fleshy, hanging appendage.

Its position directs airflow:

• Oral Sounds: The velum is raised against the back wall of the pharynx, closing off the nasal passage. Air exits only through the mouth.
• Nasal Sounds: The velum is lowered, allowing air to pass through the nasal cavity. For purely nasal sounds (like /m/, /n/, /ŋ/ in English), there is also a complete closure made somewhere in the oral cavity (e.g., lips for /m/, alveolar ridge for /n/), forcing air out through the nose.
• Nasalized Sounds: The velum is lowered, allowing air to exit through both the nose and the mouth simultaneously (e.g., nasalized vowels in French).

Mechanics of Breathing

Vocal Cord Disorders and Abnormalities

Potential Causes

• Vocal abuse or misuse (e.g., screaming, speaking in unnatural pitches, speaking loudly over noise).
• Irritants (e.g., alcoholic drinks, smoking, passive smoking, drug use, environmental pollutants).
• Environmental factors (e.g., extreme temperatures, dry air).
• Certain beverages (e.g., very cold or hot drinks, excessive caffeine).
• Habits (e.g., frequent throat clearing, incorrect breathing techniques, chronic mouth breathing).
• Infections or inflammation (e.g., laryngitis).
• Gastroesophageal reflux disease (GERD).
• Neurological conditions.

Common Conditions

1. Nodes or Nodules:
   Small, callous-like bumps, typically forming bilaterally (on both vocal cords) at the point of maximal contact, due to chronic vocal strain. Often described as ‘singer’s nodes’ or ‘teacher’s nodes’.
   • Treatment: Voice therapy, vocal hygiene education, vocal rest. Surgery is rarely needed if therapy is followed.
2. Polyps:
   Larger, often fluid-filled or blister-like growths, frequently unilateral (on one vocal cord). Can result from acute vocal trauma (like yelling) or chronic irritation.
   • Treatment: Voice therapy, vocal rest, medication (e.g., corticosteroids). Surgery (microlaryngoscopy) is often required to remove the polyp.
3. Cancer (Laryngeal Cancer):
   Malignant growth on the larynx. Risk factors include smoking and excessive alcohol consumption.
   • Treatment: Depends heavily on the stage and location; may include radiation therapy, chemotherapy, or surgery (ranging from partial laryngectomy to total laryngectomy – complete removal of the larynx).
4. Contact Ulcers or Granulomas:
   Sores (ulcers) or granulated tissue masses (granulomas) on the vocal cords, often near the arytenoid cartilages posteriorly. Potential causes include forceful voice use (glottal attacks), intubation trauma, or laryngopharyngeal reflux (acid reflux affecting the throat).
   • Treatment: Voice therapy, medication (especially anti-reflux medication), behavioral changes, sometimes surgery for persistent granulomas.
5. Laryngitis:
   Inflammation or infection of the larynx, causing hoarseness or voice loss. Can be acute (often viral) or chronic (due to ongoing irritation).
   • Treatment: Voice rest, hydration, humidification, treating the underlying cause (e.g., antibiotics for bacterial infection, reflux management for chronic laryngitis).
6. Vocal Cord Paralysis:
   Inability of one or both vocal cords to move due to damage to the recurrent laryngeal nerve or superior laryngeal nerve.
   • Unilateral (one cord paralyzed): May cause a weak, breathy voice and sometimes difficulty swallowing. Treatment can include voice therapy or surgical procedures (medialization laryngoplasty, injection laryngoplasty e.g., with fat or synthetic materials like Prolaryn Gel – Teflon is rarely used now due to complications) to move the paralyzed cord closer to the midline.
   • Bilateral (both cords paralyzed): Can severely impact breathing if cords are paralyzed near the midline, potentially requiring a tracheostomy. If paralyzed in an open position, voice is very weak/absent. Treatment focuses on ensuring an adequate airway and potentially improving voice.