Anatomy of the Larynx
The larynx (voice box) consists of four basic anatomic components:
- A cartilaginous skeleton
- Intrinsic muscles
- Extrinsic muscles
- A mucosal lining
The cartilaginous skeleton of the larynx, which houses the vocal cords, is made up of the thyroid, cricoid, and arytenoid cartilages. These cartilages are connected to other structures of the head and neck through the extrinsic muscles. The intrinsic muscles of the larynx alter the position, shape, and tension of the vocal cords.
Functions of the Larynx
The larynx functions in swallowing, breathing, and voice production. The production of voice can be thought of in terms of three components:
- The production of airflow
- The generation and resonance of sound
- The articulation of voice
Production of Airflow
The lungs first supply adequate airflow to overcome the resistance of the closed vocal cords. The vocal cords are finely tuned neuromuscular units that adjust pitch, loudness, and tone by altering their position and tension.
The following diagram illustrates the vocal cord vibration cycle that occurs 200 to 400 times a second during sound production (phonation).The rapid opening and closing of the vocal cords occur in a vibratory pattern and are responsible for sound production. Thus, any structural, inflammatory, or neoplastic lesion of the vocal cord affects voice production and quality.
- A. Vocal cords closed immediately prior to phonation (voice production).
- B. Air pressure develops below vocal cords because of air from lungs during exhalation.
- C. Vocal cords separate briefly with the release of air. (1) Arrow points to the upper edge of the vocal cord.
- D. Vocal cords re-approximate. (2) Arrow points to the lower edge of vocal cord.
- E. Vocal cords together again.
Articulation of Voice
Final modification of the voice occurs in the mouth, nose, and throat, where the tongue, palate, cheek, and lips are involved in articulation (speech production).